ACS OTHER PRIMARY EQUIPMENT

Transcription

1 ACS OTHER PRIMARY EQUIPMENT Fleet Strategy Document 31/10/2013 Transpower New Zealand Limited All rights reserved. Page 1 of 70

2 C O P Y R I G H T 2013 T R A N S P O W E R N E W Z E A L A N D L I M I T E D. A L L R I G H T S R E S E R V E D This document is protected by copyright vested in Transpower New Zealand Limited ( Transpower ). No part of the document may be reproduced or transmitted in any form by any means including, without limitation, electronic, photocopying, recording or otherwise, without the prior written permission of Transpower. No information embodied in the documents which is not already in the public domain shall be communicated in any manner whatsoever to any third party without the prior written consent of Transpower. Any breach of the above obligations may be restrained by legal proceedings seeking remedies including injunctions, damages and costs. Transpower New Zealand Limited All rights reserved.

3 Table of Contents 1 INTRODUCTION Purpose Scope Stakeholders Strategic Alignment Document Structure ASSET FLEET Asset Statistics Asset Characteristics Asset Performance OBJECTIVES Safety Service Performance Cost Performance New Zealand Communities Asset Management Capability STRATEGIES Planning Delivery Operation Maintenance Disposal Asset Management Capability Summary of RCP2 fleet strategies APPENDICES A. ADDITIONAL SCOPE DETAIL B. TYPICAL ALTERNATING CURRENT STATIONS OTHER ASSET PHOTOGRAPHS C. ASSET CONDITION ADDITIONAL INFORMATION D. ADDITIONAL STATISTICS Transpower New Zealand Limited All rights reserved. Page 3 of 70

4 EXECUTIVE SUMMARY Introduction The ACS Other fleet includes outdoor instrument transformers, disconnectors and earth switches, outdoor bus sections, including buswork and support structures, and a range of other miscellaneous ancillary equipment. The ancillary equipment at each substation also includes an earth grid and a local service system, and most have oil containment facilities. The operational integrity and performance of these ancillary assets is essential to maintaining reliability of supply to customers and to ensuring public safety. Our asset management approach for ACS Other equipment seeks to achieve an appropriate level of reliability, and to achieve the least overall lifecycle cost for these assets, as outlined below. Instrument transformers Our ACS Other fleet includes approximately 5,000 instrument transformers. Instrument transformers generally perform well, and major failures are rare. Over the past 10 years the average age of our standalone instrument transformer population has decreased, and is now around 17 years. The average age has decreased as the result of the replacement of old defective and high-risk models, upgrades to meet new protection system requirements and the addition of new equipment to our network. All practical measures will be taken to maintain this good performance and avoid the safety and reliability risks that result from explosive failures. Our approach during RCP2 is to focus on populations of ageing instrument transformers and undertake replacements to minimise the risk of catastrophic failure. We will replace approximately 496 instrument transformers during RCP2 at a forecast cost of $15.8m. The planned rate of replacement represents approximately 2% of the population each year. Disconnectors and earth switches Our ACS Other fleet includes approximately 3,900 disconnectors and earth switches The fleet of disconnectors and earth switches is highly diverse, with a wide range of makes, models and configurations. The main types of disconnector in our fleet are of a design that requires precise alignment to ensure that they close fully, and remain closed. The disconnector fleet experiences a much higher rate of forced and fault outages than our international peers. The root cause of the poor performance is the vulnerability of a large proportion of our disconnector fleet to mal-alignment, leading to disconnectors found with contacts not completely closed. The mal-alignment of disconnectors can lead to overheating of the contacts, and there have been isolated instances of meltdown of contacts. Although the forced outage rate performance is poor, the physical condition of fleet is generally good. We have identified a range of improvements that are required to condition assessment processes and decision-making frameworks to optimise long-term asset management of disconnectors. Our strategy for improving performance of disconnectors includes a strong focus on improving the competence of the workforce to achieve satisfactory mechanical alignment. The training programme for our service providers will reduce the instances of mal-alignment that is the cause of most forced and fault outages. Transpower New Zealand Limited All rights reserved. Page 1 of 60

5 However, we also plan to completely replace some of the worst performing models and models with small populations. We have recognised that the asset management information we currently have available about disconnectors and earth switches is not of sufficient quality and consistency to support fully robust and consistent decision making about priorities for replacement and refurbishment. Improvements in asset condition information and in data quality are required, and initiatives to achieve these improvements have commenced. This will enable a more systematic approach to replacement and refurbishment decisions, and the development of an asset health model for long-range forecasting. We plan to replace 173 disconnectors and earth switches during the RCP2 period at an estimated cost of $12.4m. The planned rate of replacement is approximately 1% of the fleet each year. The improvements in asset management processes outlined above are expected to lead to changes in the priority of replacements, and to some re-allocation between replacement and refurbishment. However, the forecast expenditure during the period is a minimum necessary to maintain the fleet in an overall stable condition and to lift performance during the RCP2 period. Bus systems and support structures Our ACS Other fleet includes approximately 1,078 outdoor bus sections, including buswork and support structures. Outdoor switchyard busbars are critical points of connection within the transmission system. There is a diverse range of busbar designs. There are still some vertically stacked double busbar systems in service that present unacceptable safety risks. In addition, the configuration of some structures leads to significant operational constraints. The support structures for buswork, disconnectors and earth switches are also of diverse design and configuration. They include galvanised steel and aluminium lattice structures, and steel and concrete posts. Support structures are generally in good condition. Steel lattice structures at some sites require significant work to address corrosion. At other sites, some of the concrete bus support posts installed in the 1950s and 1960s have exposed and corroding reinforcing steel, causing the concrete to crack or spall. Our asset management approach for outdoor bus systems and support structures is to bring all of our busbars and bus structures to a state where they meet the latest seismic standards, provide the required clearances for service providers to carry out maintenance work safely, and provide appropriate operational flexibility and reliability. During RCP2, we will complete the major busbar refurbishment projects that began in RCP1 at Timaru, Wilton, Hawera and Waihou to address operational and maintenance constraints and ensure that all safety requirements can be met. A further major structure and buswork project will be undertaken at Kinleith Substation, and busbar re-insulation and refurbishment projects will be completed at Maraetai and Henderson. We will also undertake a nationwide investigation to assess the condition of concrete bus support posts and determine the required remedial works. This programme will build on the results of pilot surveys and remedial works that have already been completed at six sites. The forecast expenditure for bus replacements and refurbishments during the RCP2 period is $11.6m. Transpower New Zealand Limited All rights reserved. Page 2 of 60

6 Local service systems ACS Other Primary Equipment Our ACS Other fleet includes the local service power supply systems at each site. The design and condition of local service systems vary widely. These systems often date from the original commissioning of the station. At some older sites, the various components of the local service system, including the main distribution boards, are reaching end of life, with increasing risks to reliability. At some critical sites, the overall design of the local service system requires review, to ensure that it achieves an appropriate level of reliability. We plan to survey our fleet of low voltage alternating current (LVAC) supply panels and replace those in poor condition or of unsatisfactory design, and upgrade to the latest standards. The current design standard specifies a main 400 V switchboard and a separate LVAC panel for essential supplies. Presently, at some small stations the LVAC panels and the switchboards are combined. In these cases a new main 400 V switchboard will be installed when the LVAC panel is replaced. Based on a desktop study of current age and condition, we estimate that 34 LVAC panel replacements will be required during RCP2, at a forecast cost of $3.3m. In addition to these LVAC panel replacements, we will complete a major upgrade of the local service system at Islington Substation that commenced in RCP1. Improvements In our planning for RCP2 period we have made a number of improvements to the asset management of ACS Other equipment. Our planning decisions consider the whole-of-life of ACS Other assets covering planning, delivery, operations, maintenance and disposal, as well as their impacts on other assets, including circuit breakers and power transformers. Cost estimation for projects in RCP2 have been undertaken using tailored building blocks based on actual cost out-turns from completed or equivalent works. Further improvements during RCP2 will include: a comprehensive review of the asset management approach for disconnectors and earth switches, including the condition assessment framework and decision-making tools refinement of data collection and condition assessment techniques for a variety of assets, including buswork and support structures, local service systems and outdoor junction boxes (ODJBs) refinement and implementation of the asset criticality framework. Transpower New Zealand Limited All rights reserved. Page 3 of 60

7 SUMMARY OF STRATEGIES Main strategies The following summaries include the main strategies and their respective costs during the RCP2 period ( ). The main strategies are all capital expenditure strategies, which focus on replacing the above assets over the RCP2 period to improve the overall safety and reliability performance of the asset fleet. Capital expenditure Replace Instrument Transformers RCP2 Cost $15.8m Our strategy is to focus on populations of ageing instrument transformers, and undertake replacements to minimise the risk of catastrophic failure. The programme of work will include detailed examination of samples of ageing populations, to assist risk management and prioritisation. The plan will result in replacement of 2% of the population each year. We plan to replace 496 instrument transformers over the RCP2 period at an estimated cost of $15.8m. Replace Disconnectors and Earth Switches RCP2 Cost $12.4m Our strategy is to improve performance and reduce the complexity of asset management by completely replacing some of the worst performing models and other units in poor condition, and replacing models with small populations. Where it is economic, refurbishment will be used to extend the lives of some of our main models, as an alternative to replacement. The plan as submitted is for replacements alone, and will result in replacement of approximately 1% of the population each year. Planned asset management process improvements will lead to some re-prioritisation, and re-allocation from replacement to refurbishment. We plan to replace 173 disconnectors and earth switches over RCP2 at an estimated cost of $12.4m. Transpower New Zealand Limited All rights reserved. Page 4 of 60

8 Replace or Refurbish Bus Systems RCP2 Cost $11.6m Our strategy is to replace or refurbish busbar systems at 50 kv 1 and above that present realtively high safety or performance risks or impose significant operational constraints. This will reduce the likelihood of outages and safety incidents. As part of the Kinleith Substation rebuild project, we plan to spend approximately $5.5m on replacing the 110 kv structure and associated buswork. During RCP2, we also plan to complete the last of five bus projects that began in RCP1 at Timaru, Wilton, Hawera and Waihou. The total forecast expenditure for bus system replacement and refurbishment for the RCP2 period is $11.6m. Replace and Upgrade Substation Local Service RCP2 Cost $6.3m Our strategy is to replace substation LVAC panels in poor condition and install a main 400 V switchboard as required. This will lead to reduced failure risk for these important assets. We plan to replace LVAC panels and switchboards at 34 sites over RCP2 at an estimated cost of $3.3m. In addition, we plan to complete a major upgrade of the local service system at Islington Substation that began in RCP1, at an estimated cost in RCP2 of $3.0m. Chapter 4 has further details on these strategies and a discussion of the remaining strategies. 1 This is in addition to the 33 kv switchyard replacement programme described in the Outdoor 33 kv Switchyard strategy. Transpower New Zealand Limited All rights reserved. Page 5 of 60

9 1 INTRODUCTION Chapter 1 introduces the purpose, scope, stakeholders, and strategic alignment of the AC Stations Other Primary Equipment Fleet Strategy. 1.1 Purpose We plan, build, maintain and operate New Zealand s high-voltage electricity transmission network ( Grid ) which includes a range of ancillary equipment in AC substations ( ACS Other ). These assets play an important role in enabling the safe and reliable operation of substations. The purpose of this fleet strategy document is to describe our approach to the lifecycle management of the ACS Other fleet. This includes a description of the asset fleet, objectives for future performance and strategies being adopted to achieve these objectives. The strategy sets the high-level direction for asset management activities across the lifecycle of the assets. These activities include Planning, Delivery, Operations, Maintenance, and Disposal. This document has been developed based on good practice guidance from internationally recognised sources, including BSI PAS 55: Scope The scope of the strategy includes the following substation ancillary equipment for 50 kv and above: free- standing instrument transformers 2 outdoor disconnectors and earth switches 3 outdoor buswork, including support structures and lightning protection earthing resistors surge arrestors local service supply low voltage alternating current (LVAC) oil containment outdoor junction boxes (ODJBs) earth grids. Major primary AC station equipment fleets are covered in separate dedicated strategies and the types of equipment above for 33 kv and below are described in the Outdoor 33 kv Switchyard Fleet Strategy. Further detail on the scope of this fleet strategy is provided in Appendix A. Photographs of typical AC station equipment are provided in Appendix B. 2 3 Integral instrument transformers are treated as a component of the associated switchgear and are not included in the scope of this document. See the indoor switchgear and the outdoor circuit breaker strategies. Disconnectors and earth switches that are part of indoor switchgear, including gas insulated switchgear, are covered by the Indoor Switchgear Fleet Strategy Transpower New Zealand Limited All rights reserved. Page 6 of 60

10 1.2.1 Exclusions The following are not covered in this fleet strategy: ACS Other Primary Equipment instrument transformers, disconnectors and other equipment that is integral to indoor switchgear disconnectors and other AC substation primary equipment in outdoor structures operating at voltages below 50 kv disconnectors and earth switches that are integral to outdoor disconnecting circuit breakers instrument transformers that are components of outdoor dead tank circuit breakers equipment associated with the HVDC system relays, switches, AC/DC supplies and secondary wiring in ODJBs. The equipment listed above is covered as part of other fleet strategies. 1.3 Stakeholders ACS Other assets are important components of the transmission system. Correct operation and maintenance of this equipment is essential for the safe and reliable operation of substations. The key stakeholders for this asset fleet include: Transpower Groups: Grid Development, Performance and Projects service providers regulatory bodies: Commerce Commission and Electricity Authority customers, including distribution network businesses and generators. 1.4 Strategic Alignment A good asset management system shows clear hierarchical connectivity or line of sight between the high-level organisation policy and strategic plan, and the daily activities of managing the assets. This document forms part of that connectivity by setting out the strategy for managing ACS Other equipment to deliver our overall Asset Management Strategy. Transpower New Zealand Limited All rights reserved. Page 7 of 60

11 This hierarchical connectivity is represented graphically in Figure 1 below. It indicates where the fleet strategy and plans fit within our asset management system. As shown in Figure 1, this fleet strategy directly informs the Asset Management Plans. Corporate Objectives & Strategy Asset Management Policy Asset Management Strategy Lifecycle Strategies Planning Delivery Operations Maintenance Disposal ACS Other Equipment Strategy Disconnectors & Earthswitches Plan Instrument Transformers Plan Other Station Assets Plan Figure 1: The ACS Other Fleet Strategy within the Asset Management Hierarchy 1.5 Document Structure The rest of this document is structured as follows. Chapter 2 provides an overview of the ACS Other fleet including fleet statistics, characteristics and their performance. Chapter 3 sets out asset management related objectives for the ACS Other fleet. These objectives have been aligned with the corporate and asset management policies, and with high-level asset management objectives and targets. Chapter 4 sets out the fleet specific strategies for the management of the assets. These strategies provide medium-term to long-term guidance and direction for asset management decisions and will support the achievement of the objectives in chapter 3. Appendices are included that provide further detailed information to supplement the fleet strategy. Transpower New Zealand Limited All rights reserved. Page 8 of 60

12 2 ASSET FLEET Chapter 2 provides an overview of the ACS Other asset fleet, including: Asset statistics: including population, diversity, age profile and spares Asset characteristics: including safety considerations, asset criticality, asset condition, maintenance requirements and interaction with other assets Asset performance: including reliability, safety, and risks and issues. Our 178 AC substations 4 contain a large number of individual assets that collectively form the Grid. The ACS Other fleet provides a variety of functions to support the operation of these installations. 2.1 Asset Statistics This section outlines the population of the ACS Other asset fleet, its diversity and age profiles. The asset fleet includes: instrument transformers disconnectors and earth switches outdoor bus systems other ancillary equipment Asset Population Instrument transformers The purpose of instrument transformers is to convert high voltages and currents to lower levels that can be safely measured by instrumentation and protective equipment. We have approximately 5,000 freestanding (standalone) units 5 rated 50 kv to 220 kv in service at our AC stations. An additional number of instrument transformers are integrated within larger primary equipment - such as indoor gas insulated switchgear (GIS) and outdoor dead tank circuit-breakers - and are not considered in this document. Table 1 details the numbers of the four types of instrument transformers. 4 5 Total number of sites where there is primary station equipment owned and operated by Transpower A single phase free-standing instrument transformer is represented as a single unit. However, a freestanding instrument transformer with all three phases in one integrated assembly is also represented as a single physical unit. The majority of instrument transformers are single phase units. Transpower New Zealand Limited All rights reserved. Page 9 of 60

13 Type Total Current transformers 3,270 Capacitor voltage transformers (CVTs) 948 Voltage transformers 667 Neutral current transformers (NCTs) 77 Total 4,962 Table 1: Instrument transformer population as at June 2013 Disconnectors and earth switches Disconnectors are mechanical devices used to isolate major equipment from high voltages for maintenance or operational purposes. The isolated equipment may include power transformers, circuit breakers, interconnected buses and transmission lines. The majority of the 50 kv and 110 kv units are manually operated whereas the majority of the 220 kv units are motor operated. Earth switches are used to ensure that isolated equipment is safe to work on. They protect personnel from accidental livening of the equipment and risks arising from induced voltages from adjacent equipment. They are mostly manually operated, and are used to connect the high-voltage conductors on buses, power transformers and other equipment to earth. We have approximately 2,900 freestanding disconnectors (including disconnectors installed with integral earth switch arms) and approximately 900 standalone earth switches in service at our AC stations. Table 2 details the numbers of freestanding disconnectors and earth switches. Type Population Disconnectors 2,929 Earth switches 929 Total 3,858 Table 2: Population of disconnectors and earth switches at June 2013 Note: An additional number of disconnector and earth switches are integral within larger primary equipment such as indoor GIS and outdoor disconnecting circuit breakers and are not included in this document. Outdoor bus systems We have 199 installations that contain outdoor buswork and support structures. 6 Outdoor bus systems are switchyard structures comprising of gantries, lattice structures, high-voltage conductors, associated primary clamps/accessories, support posts and insulators. The majority of our sites have a number of switchyard structures of different voltages, sometimes including two or more structures of the same voltage. The various types of structures in service include older, high-level galvanised and aluminium lattice structures with flexible conductors, and low-level rigid busbars mounted on concrete or steel posts with insulators. A few substations have outdoor-type structures and equipment which are housed indoors, such as at the New Plymouth Substation. 6 This document only considers outdoor buswork and support structures for voltages above 50 kv. For 33 kv and below outdoor buswork and support structures, see the Outdoor 33 kv Switchyard Fleet Strategy. Transpower New Zealand Limited All rights reserved. Page 10 of 60

14 Lightning protection systems ACS Other Primary Equipment A lightning strike inside a substation can have widespread effects on electricity networks and can pose a significant risk to personnel in the area. Damage to equipment caused by a lightning strike can be extremely costly and time consuming to repair. Our substations are designed with lightning protection to reduce the likelihood of a lightning strike on high-voltage equipment. HV buses and equipment are generally protected from lightning strikes using lightning masts, rods, overhead earthwires or surge arresters. Our standard lightning protection design for new installations includes lightning masts and spikes, along with surge arresters integrated with power transformers. Other equipment Table 4 shows the population of other equipment by type and voltage. Type Voltage kv 110 kv 220 kv N/A Total Neutral Earthing Resistors (NER) Surge arresters ,375 Neutral Earthing Resistors (NER) Table 3: Populations of other assets as of June 2013 Neutral earthing resistors (NERs) are associated with HV power and earthing transformers. Their purpose is to limit fault currents and ensure the correct operation of protection equipment when an earth fault occurs. They are connected between the neutral point of a star-wound, high-voltage power transformer winding and earth. The majority of our NERs are freestanding, with the rest being integrated with earthing transformers. Surge arresters Prior to the installation of surge arresters, rod gaps and arcing horns were used to protect equipment from overvoltages due to lightning strikes and switching surges. These were generally unreliable and caused a relatively large number of outages from flashovers due to weather conditions, wildlife and flying debris getting between the electrodes. In addition they were also found to cause radio interference in damp weather. The early surge arresters were a gap type. These were unreliable and often failed explosively on operation. Newer and more reliable gapless metal oxide surge arresters were introduced in the mid-1970s, and these have replaced the older overvoltage protection devices. We have approximately 1,375 outdoor, freestanding gapless surge arresters rated 50 kv to 220 kv in service. All high-risk sites for lightning strikes or switching surges have been identified and mitigated by the installation of surge arresters. A few of the older surge arresters remain at New Plymouth and Rangipo. Some other sites still have rod gaps and arcing horns. The remaining older surge arrestors and rod gaps will be removed as a priority during RCP1 and RCP2. Local service supply The 400/230 V AC local service electrical supply is normally sourced from one or more local service transformers connected to the medium-voltage or low-voltage busbars at the station or from a metered connection to the local distributor s system. Transpower New Zealand Limited All rights reserved. Page 11 of 60

15 The local service transformers are connected by cable to an indoor AC main 400/230 V switchboard or LVAC panel. The main 400 V switchboard and LVAC board control and distribute local service power to the station services, including essential and non-essential equipment, such as: DC battery chargers transformer cooling fans and pumps circuit breaker operating mechanisms switchyard and control building lighting and power outlets communication equipment and some control equipment emergency lighting and security systems building services including air conditioning oil separator units drainage All stations have at least one 400 V board, with some of the larger sites having extensive local service distribution systems with multiple distribution boards. At 11 sites, the local service system includes a standby generator. Oil containment Sites with major oil-filled equipment such as power transformers generally have one or more oil containment facilities to contain oil leaks and spills. At a few sites, oil containment facilities are yet to be installed. The oil containment facilities are required to meet our obligations under the Resource Management Act. The residual levels of oil in stormwater discharged from the site must be kept within permissible levels set by local authorities. Oil containment mitigates the risk of oil contamination of the surrounding land and waterways by capturing oil spills and leaks, and removes oil from stormwater before stormwater is discharged into the environment. There are oil containment systems in service at more than half of our substations. These facilities typically comprise bunded areas around oil-filled equipment, oil/water separators and underground oil containment tanks of sufficient volume to hold the oil from the largest oil-filled item on site. The oil separators in use include gravity, American Petroleum Institute (API) standard, and plate types. The standard design for new oil containment facilities is to use a bulk oil containment tank with a plate separator to remove the oil from stormwater effluent. There are currently 48 plate separator systems in service. A secondary benefit of oil containment drains and tanks is that, in the event of a transformer explosion and oil fire, they help to extinguish burning oil flowing from the transformer. Earth grids Earth grids are a network of copper conductors buried in the ground beneath substation switchyards to ensure electrical safety during earth fault conditions. A station earth grid normally has a long life (in excess of 50 years) and requires little attention. However, it may require modification if the projected fault current increases beyond the original design level, or if the switchyard is extended. Transpower New Zealand Limited All rights reserved. Page 12 of 60

16 Switchyard surfacing plays an important role in conjunction with the earth grid, in ensuring electrical safety for personnel during fault conditions. The switchyard surfacing provides an insulating layer that helps to mitigate the risks of step and touch potential hazards during fault conditions. The condition, maintenance and refurbishment of switchyard surfacing is covered in the Buildings and Grounds Fleet Strategy. Outdoor junction boxes Most of our substations have ODJBs, which serve multiple purposes. They provide a cabling interface point in the switchyard for most of the critical control and protection functions of the station. Specific functions implemented in ODJBs may include isolation switches for bus-zone protection, and isolation switches and loading resistors for instrument transformers. These isolation switches allow equipment to be safely taken out of service for maintenance or repairs. The ODJBs also provide a point of connection for the distribution of AC and DC supplies in the switchyard. They provide power for the operating mechanisms of circuit breakers, motor operated disconnectors, anti-condensation heating, and other functionality to support operational equipment. The relays, switches, AC/DC supplies and secondary wiring in the ODJB are considered in the Secondary Assets Fleet Strategy Fleet Diversity Asset fleet diversity is an important asset management consideration, with implications for interchangeability and contingency response, spares holdings, maintenance support, condition assessment and asset health forecasting, asset knowledge and training. Instrument transformers Diversity of the fleet is diminishing as older equipment is replaced with newer standard equipment purchased from a few preferred manufacturers. However, there is still a reasonably high level of diversity in the fleet of current transformers, as shown in Table 4. Type Voltage kv No of Manufacturers No of Models Current transformers Capacitor voltage transformers Voltage transformers Neutral current transformers N/A 8 32 Table 4: Diversity of Instrument Transformers Instrument transformers are mostly readily interchangeable, because they are freestanding and the majority have standard ratings. Diversity is still an issue, but is less of a problem than for other equipment. Transpower New Zealand Limited All rights reserved. Page 13 of 60

17 Disconnectors and earth switches ACS Other Primary Equipment From the 1960s to 1990s we purchased most of our disconnectors and earth switches from one company. A number of other manufacturers were invited to tender in the 1990s and, as a consequence, the fleet became more diverse from that time. The present disconnector fleet compromises approximately 126 models. In addition to the manufacturer diversity, there are seven different configurations with different current and fault ratings, which are: single side break disconnector vertical break disconnector centre rotating double break disconnector centre break disconnector rocking post disconnector pantograph disconnector vertical earth switch. Table 5 shows the diversity of the fleet by manufacturer and model. Type Voltage kv No. of Manufacturers No. of Models Disconnectors Earth switches Total Table 5: Diversity of disconnectors and earth switches The fleet includes approximately 20 families of broadly similar disconnectors, with at least 10 (and often hundreds) of individual assets in each family. However, there are also another 20 models of disconnectors with less than 10 individual assets of each type. The diversity of the disconnectors and earth switches will reduce somewhat during RCP2, as we intend to totally replace some models that have small individual populations. The replacement programme is described in subsection Outdoor bus systems Bus systems include high-voltage conductors (flexible and rigid), support structures, mechanical clamps and compression fittings, termination hardware, and insulators. Most new outdoor bus structures are the low-level type mounted on galvanised steel posts, but there is a diverse range of older structures in service, as shown in Table 6. Transpower New Zealand Limited All rights reserved. Page 14 of 60

18 Support structures Type Aluminium lattice structures Galvanised steel lattice structures Reinforced concrete posts Galvanised steel posts Installation Era and Purpose Strung busbars, disconnectors, and line terminations pre-1970 Strung busbars, disconnectors, pre-1985 Tubular conductor busbar supports, disconnectors, earth switches, instrument transformers from the 1960s to 1985 ACS Other Primary Equipment Tubular conductor busbar supports, disconnectors earth switches, instrument transformers since 1985 (new line terminations since 1990) Wood poles Conductors Type A few older substations, mostly rural Table 6: Support Structures Installation Era and Purpose Installation Era Flexible stranded conductor strung busbars (copper) Flexible hollow-core conductor strung busbars (copper) Tubular and channel supported busbars (copper) Flexible stranded conductor strung busbars (aluminium alloy) 1940s 1980s substations 1940s 1980s substations 1960s 1970s substations 1980s present substations Insulators Tubular and channel supported busbars (aluminium alloy) 1980s present substations Table 7: AC Stations conductor types and era Type Cap and pin porcelain insulators Porcelain disc insulators Glass disc insulators Insulator use/age Busbar support and disconnectors pre 1980 Strung bus pre 1970 (no longer used) Strung bus post 1970 to present day Solid core porcelain post insulators Composite long rod insulators Busbar support and disconnectors since mid-1980s to present day Strung bus in highly contaminated areas since late 1990s to present day Table 8: AC Stations insulator types and era Diversity of other assets NERs The NERs were supplied by nine manufacturers. Although some standardisation in ratings has been applied, most units are customised to suit the site. The main types of resistors are metal grid resistors and liquid resistors. We have a number of freestanding NERs rated up to 66 kv. By 2015, the last of the liquid resistors will have been removed from service, and all remaining resistors will be air-insulated, stainless steel element types. While the diversity in ratings limits interchangeability, the units are very reliable. Surge arresters Since the mid-1980s, all surge arresters purchased have been the gapless type and purchased from three manufacturers. The majority have standard ratings. Diversity is not a Transpower New Zealand Limited All rights reserved. Page 15 of 60

19 major problem as the surge arresters of different makes and types are readily interchangeable. Local service supplies The local service transformers, switchboards and LVAC Boards, including high-voltage cables and low-voltage cables are of highly diverse design and manufacture. However, in general, replacements for this class of equipment are available at relatively short notice from local suppliers who also supply this equipment to many other end users. As a result, the diversity in design and manufacture of local service equipment does not lead to significant risks. Oil containment facilities There are several types of oil spill containment systems in service. The design of each system is customised for the station and local weather conditions. The plate separator systems are the most critical items from a risk perspective, but replacement equipment is generally available from local suppliers because they are common assets in many industries, and so diversity does not lead to significant risks. Earth grids While earth grids comprise of different sized copper conductors depending on the fault level, diversity is not an issue as copper conductors are readily available from the market and have very short lead times Age Profile Our assets have been installed progressively, with particular periods of Grid development in the 1930s and the 1950s 1980s. The average life expectancy across the fleet is upwards of 50 years. A large proportion of station assets installed in the 1950s 1970s are nearing the end of their expected life. Life expectancy is the nominal life established for fixed asset accounting purposes. It represents the typical average life that is expected from a type of equipment before it is no longer fit to remain in service. Transpower New Zealand Limited All rights reserved. Page 16 of 60

20 Instrument transformers ACS Other Primary Equipment The average age of our standalone instrument transformer population has steadily decreased over the past decade, and is now around 17 years (see Figure 2). The decrease in average age is the result of the replacement of old defective and high-risk models, upgrades to meet new protection system requirements, and additions of new equipment to the network. Manufacturers estimate that the life of an instrument transformer is years. Yet our experience is that well-designed and well-built instrument transformers can have a useful life of up to 50 years. INSTRUMENT TRANSFORMER - AGE PROFILE CTS VTS CVTS AGE (YEARS) Disconnectors and earth switches Figure 2: Instrument Transformers Age Profile Under normal operating and environmental conditions, disconnectors and earth switches have life expectancies in excess of 55 years. Yet they typically require more maintenance as they age, because operating mechanisms and lubricants deteriorate over time. The age profile shown in Figure 3 is based on the date of original installation. However, many disconnectors have had component replacements in the intervening period, including the renewal of support insulators, contacts, auxiliary switches and earth braids. The effect of these component replacements is to significantly extend the expected lives of the disconnector as a whole. DISCONNECTOR AND EARTHSWITCH - AGE PROFILE DISCONNECTORS EARTH SWITCHES AGE (YEARS) Figure 3: Disconnectors and Earth Switches Age Profile A relatively large number of disconnectors and earth switches will begin reaching the end of their nominal life expectancy by the beginning of the RCP3 period in However, as Transpower New Zealand Limited All rights reserved. Page 17 of 60

21 outlined above, many disconnectors have had renewals of components, leading to significant extensions to life expectancy. Outdoor bus systems The life expectancy of all types of outdoor bus systems is approximately 55 years. The age profile show in Figure 4 relates to the age of initial installation. However, many of the bus systems have had components replaced in the interim and include extensions that were installed more recently. BUS SYSTEM - AGE PROFILE AGE (YEARS) Other equipment age profile Figure 4: Bus System Age Profile The age profiles of the fleets of other station equipment covered by this strategy are summarised in Tables 9 to 12, along with their nominal life expectancy. The expected life of the equipment has been estimated by taking into account our experience, other utilities experience, and the manufacturer s recommendations. NERs Type Average Age (years) Life Expectancy (years) Earthing resistors Surge arresters Local service systems Oil containment Earth grids Table 9: Other Equipment Average Age and Life Expectancy Our metal grid NERs are relatively modern, with the older liquid type currently being phased out. The average age of the metal type resistor is approximately 9.2 years whereas the liquid type resistors are approximately 30 years of age. The life expectancy of an NER is 50 years. The actual rated voltages differ slightly from the system voltages, so they have been grouped into the nearest standard voltage. Transpower New Zealand Limited All rights reserved. Page 18 of 60

22 Type Voltage kv Average Age (Years) Life Expectancy Metal Surge arresters Liquid Overall Table 10: Other Equipment Average Age and Life Expectancy Modern gapless surge arresters have almost completely replaced the older and unreliable gap-based models. Gapless type surge arresters have been in service for less than 20 years and the expected life expectancy of 40 years is a conservative estimate that has not yet been proven. Type testing has determined that these units deteriorate in proportion to the number of operations and fault current, so the life of the surge arrester will depend on its location within the transmission system. Local service systems Voltage (kv) Average Age (Years) Life Expectancy Overall Table 11: Surge Arresters - Average Age and Life Expectancy The age profile of the various components of local service systems are discussed below. Local service transformers Voltage (kv) Average Age (Years) Life Expectancy Overall Table 12: Local Service Transformers - Average Age and Life Expectancy Switchboards and LVAC panels The nominal life expectancy of local service systems is 55 years. Approximately 20% of the switchboards and LVAC panels is aged 60 years or more, and the balance of the population has an average age of 45.5 years. Transpower New Zealand Limited All rights reserved. Page 19 of 60

23 Local service power cables ACS Other Primary Equipment The low-voltage (400 V) cables in the local service system are not individually recorded in the asset management system. The older paper-insulated cables are often replaced when the local service switchboard or LVAC panel is replaced or upgraded. On this basis, the average age of cables would be similar to that of the associated local service transformer, switchboard and LVAC panel Spares There is a wide variation in the spares required for the equipment classes covered by this strategy, based on the expected modes of failure, the criticality, and the expected lead times for procurement of items needed for repair or replacement. The three classes of spares held are: unit spares new standard units specifically purchased as national strategic spares component spares unused units purchased as spares for site specific use decommissioned spares removed from service in good serviceable condition. Instrument transformers spares Current Transformers The current transformers (CTs) have two standard ratings, 1200 A and 2400 A. Outside of this, there are a few CTs with a higher rating of 4000 A. The minimum number of standard CTs required to be held as spares is six of each rating at each common voltage (66 kv, 110 kv, and 220 kv). Voltage transformers and capacitor voltage transformers The minimum number of voltage transformers (VTs) and capacitor voltage transformers (CVTs) required to be held as spares is six of each rating of 220 kv CVT and three 110 kv CVTs, as well as six 110 kv VTs and three 66 kv and 50 kv VTs. Disconnectors and earth switches spares Disconnectors and earth switches are important for operational efficiency, but are not critically essential for the operation of the transmission system. In the event of a failure, disconnectors may be temporarily bypassed with overhead conductors/jumpers 7 and temporary earths may be used as replacements for the earth switch. As a consequence, complete unit spares for this type of equipment are not a high priority. The normal component spares for a disconnector and earth switch are three phase sets of current carrying components, sets of interlocking solenoids and motor drives. A number of complete disconnectors and earth switches of various types are held in stock. Outdoor bus systems The outdoor bus systems comprise support structures, as well as the buswork conductors and insulators. 7 Bypassing disconnectors can lead to significant operational difficulties and disruptions for customers and is only considered as an emergency measure. Transpower New Zealand Limited All rights reserved. Page 20 of 60

24 There is no formal spares policy for support structures, mainly because they rarely fail and parts may be manufactured quickly in an emergency for temporary repair. There are four types of buswork: rigid, flexible, aluminium and copper. Quantities of standard size conductors and fittings are held in our warehouses and by service providers. The warehouses stock a number of insulators with a minimum reorder level to meet expected maintenance requirements and to have a few available for projects. The insulators stored are standard units and are fully interchangeable with the majority of insulators in service. Other equipment Surge arresters Our spares requirement is that a minimum of three spare surge arresters (of each voltage rating) be held. Local Service Transformers There is no formal policy on the number of spare local service transformers but there are a number of local service transformers of different voltages and ratings in stock. Switchboards and LVAC panels There are no complete switchboard or LVAC panel spares. Faulty switchboard and LVAC equipment (such as switches or fuses) can generally be replaced with off-the-shelf components, often of different manufacture and type, so there has been no need to stock spares. Most LVAC panels also have provision for a diesel generator connection as an emergency backup. Earth grids Earth grids are constructed from either flexible copper conductors or rectangular copper straps. Drums and lengths of conductors are held, in the warehouses and by contractors, largely for project work. Sections of earth grids typically deteriorate gradually in service rather than experiencing a sudden failure, so their replacement can be planned in advance without the need for spares. However, the theft of sections of earth grids requires access to spare conductors to enable immediate repair. 2.2 Asset Characteristics The ACS stations other primary equipment can be characterised according to: safety and environmental considerations asset criticality asset condition maintenance requirements interaction with other assets emerging technologies. These characteristics and the associated risks are discussed in the following subsections. Transpower New Zealand Limited All rights reserved. Page 21 of 60

25 2.2.1 Safety and Environmental Considerations ACS Other Primary Equipment We are committed to ensuring that safety and environmental risks are minimised at all times. Safety considerations Instrument transformers consequences of major failure Almost all of our freestanding instrument transformers use porcelain insulators. Although major failures of instrument transformers are rare, explosions have been known to occur. Explosive failures typically result in shards of porcelain being projected considerable distances, with the potential to cause serious harm. Working at heights The existing structures present significant falling hazards. Maintenance of the physical structure, buswork, disconnectors and earth switches as well as instrument transformers may require work at heights of 3m to 20m. Access to low-level buswork is typically carried out with the use of mobile elevating work platforms or scaffolding to reduce the risk of falls. High-level buswork may be accessed using high lift cranes for heavy and large components. Access by climbing the lattice structure may be required in some circumstances, but this increases the risk of injury from falls or other incidents. We are working to improve the safety of our bus structures through refurbishment in RCP1 and RCP2 (see subsection 4.1.2). The programme of conversions of outdoor 33 kv switchyards to indoor switchgear is largely driven by safety considerations. This programme is described in the Outdoor 33 kv Switchyard Fleet Strategy. Earth potential rise and transferred potentials The station earth grid provides an essential safety function by dissipating fault currents into the ground without creating excessive earth voltage rise and hazards to people or damage to other equipment. All stations have an earth grid that covers the entire area of the switchyard (as well as some area outside it). Larger stations may have two or more smaller interconnected earth grids. An earth grid must be sufficiently rated for the fault currents that can occur at a particular site. The design of the earth grid also takes into account the resistivity of the ground beneath the switchyard. An earth fault in the transmission network can lead to large currents flowing into the ground via the earth grid. These earth fault currents can reach thousands of amps and can temporarily raise the voltage on equipment and on the surface of the ground to dangerous levels. The voltages present during earth fault conditions can be a serious hazard because of the risk of electrocution caused by current flowing between a person s legs or between one leg and an arm touching an earthed metal object. The earth grid is designed to provide an effective safety function by keeping these step and touch potentials to within approved limits. The switchyard ground surfacing is an important factor in the safety performance of the station earth grid in the event of an earth fault. At most substations, the earth grid design relies on the provision of a surface layer of high resistivity crushed aggregate. Transpower New Zealand Limited All rights reserved. Page 22 of 60

26 Hazardous electrolyte ACS Other Primary Equipment The electrolyte used in liquid resistors is corrosive to the skin, eyes, and respiratory tract. It may also be carcinogenic. Suitable personal protective equipment must be worn when handling electrolyte. Care must be taken to ensure that any spilt electrolyte does not enter any waterway or storm water system. This type of equipment is being phased out, and the last of its type will be removed from service by Environmental concerns Oil spills Oil spills are a serious environmental concern because they can easily enter waterways, leading to widespread environmental damage. Once oil spills enter waterways, it is very difficult to remediate the area. Oil spills can occur during oil filling or emptying, or during on line oil treatment. The quantity of oil spilled in these cases could be hundreds of litres. The worst oil spill will occur with an explosive failure of a power transformer that may result in the spill of several thousands of litres of oil. This may sometimes be accompanied with an oil fire in the transformer which may last for days. Such major failure and oil spill events are very rare. As outlined in subsection 2.1.1, sites with major oil-filled equipment such as power transformers generally have one or more oil containment facilities to contain oil leaks and spills. Service providers working with oil-filled equipment are required to have oil spill kits on hand to contain and mop up small oil spills. For larger oil spills, each station has one or more oil spill kits sized to deal with oil spills up to 1,000 litres Asset Criticality We have established a process to determine and model criticality based on consideration of the importance of the site or circuit in terms of the load carried; the level of reliability required by the relevant customer; constraints and effects that would be placed on the rest of the Grid in the event of a failure; and the level of redundancy. Based on these factors we have established a framework for assigning asset criticality, which classifies all assets as low, medium, or high criticality. This approach is at an early stage of development and implementation, so it will continue to be refined and improved over RCP2. Further information on the asset criticality approach is provided in the document Asset Risk Management Criticality Framework. Asset management is adapted to recognise the differing levels of criticality to mitigate the risk of failures at critical sites and circuits and to allow less capital expenditure at sites that are less critical. The strategies in chapter 4 demonstrate how criticality is considered in asset management, particularly through earlier or later replacement and more or less frequent maintenance. Criticality of the ACS Other fleet is generally linked to either the criticality of the primary assets to which they connect or the substation in which they are located. Transpower New Zealand Limited All rights reserved. Page 23 of 60

27 Figures 5 and 6 show the proportion of instrument transformers and disconnector and earth switches in each criticality category. INSTRUMENT TRANSFORMERS - CRITICALITY LOW (51%) MEDIUM (38%) HIGH (11%) Figure 5: Instrument Transformers Criticality DISCONNECTORS AND EARTHSWITCHES - CRITICALITY LOW (44%) MEDIUM (45%) HIGH (11%) Figure 6: Disconnectors and Earth Switches Criticality Asset Condition Asset condition refers to the most recently observed physical condition of an asset by field personnel during a condition assessment. Condition assessment for ACS Other assets is scored on a scale of 1 to 10, with 1 representing assets in poor condition (or with a high failure rate), and 10 representing assets that are in an as new condition. The following discussion outlines the condition of the ACS Other fleet. Instrument transformers In general, based on the results of visual inspections and condition assessment tests, the fleet is in good condition. 8 Disconnectors and earth switches Condition assessment information for disconnectors and earth switches is available from records in our maintenance management system. 8 See subsection for a fuller discussion of the condition assessment and risks of older instrument transformers. Transpower New Zealand Limited All rights reserved. Page 24 of 60

28 Figure 7 shows that the majority of the fleet currently has a reported condition assessment score between 8 and 10. However, as outlined in subsection 2.3.3, we have recognised significant limitations in the validity and usefulness of the current condition assessment data, and have initiated a programme of major improvements. DISCONNECTORS AND EARTH SWITCHES - CONDITION RANGE 0-2 (1%) 2-5 (2%) 5-8 (39%) 8-10 (59%) Figure 7: Disconnectors and Earth switches - Condition Appendix C contains details of the condition indicators currently used for the disconnector fleet. Outdoor busbar systems Many older stations have steel lattice gantry structures. Some of these are now showing significant signs of corrosion. At some sites, the steel structures have been painted to extend their lives. At a few sites, corrosion has advanced to the point where replacement of gantry sections is required. Aluminium lattice structures are found at a few substations. Their condition is generally good, but they are prone to distortion if the strung bus is replaced with a larger conductor or heavier disconnectors with uprating of the busbar. The concrete posts installed in the 1950s and 1960s are deteriorating at many sites, and reinforcing steel is exposed and corroding causing posts to crack or spall. The deterioration may affect a post s mechanical strength and its strength needs to be reviewed to ensure it meets current seismic requirements. A previous concrete post refurbishment project at six stations found an average of 5% of the concrete posts on the station were cracked with chunks of concrete missing and the reinforcing steel exposed. Most of the cracked posts could be repaired with only a few needing replacement. A site-by-site investigation is planned for RCP2 (see subsection 4.4.2) to determine the extent and magnitude of the problem and to prepare a plan for refurbishment or replacement of the damaged posts. Galvanised steel posts are generally in good condition. However, the performance of the grouting under the post baseplates has often proved unsatisfactory. Grout shrinkage lets water in, resulting in corrosion of the baseplate and holding-down bolts. Lightning protection In the last five years, surveys and detailed lightning protection studies were carried out at 24 substations. It was found that three of those substations were seriously deficient and the issues have since been remedied. Another preliminary survey identified a further 17 additional substations requiring detailed lightning protection studies. This is addressed in subsection Transpower New Zealand Limited All rights reserved. Page 25 of 60

29 Resistors ACS Other Primary Equipment All of our metal grid resistors are in reasonable condition and require very little maintenance. The last of the electrolyte resistors will be replaced with metal grid resistors during the RCP1 period. Surge arresters Modern surge arresters are exceptionally reliable and are relatively maintenance free. A basic in-service visual inspection is carried out annually. A more thorough inspection is carried out when the associated branch is released from service for work on adjacent equipment, typically every four years. These inspections show that the fleet is in very good condition. There are a small number of the older type of surge arresters (gap type) that are much less reliable than the modern gapless types, regardless of condition. We aim to replace all of these during the RCP2 period, as described in subsection Local service systems The local service systems and associated components often date from the original commissioning of the substation site. As a consequence, the local service equipment is often considerably older than most of the main station equipment. Recent detailed condition assessments of a number of LVAC boards with deteriorated components has highlighted the need to place additional focus on these assets, particularly at older sites. The age of many of the components in local service systems is now beyond their expected lives. Many of the older local service transformers have compound-filled cable boxes that make the transformers difficult to maintain and test, and consequently their condition is unknown. The older cables are armoured, lead-sheathed, paper-insulated types. A number of these have failed as a result of the lead cracking with cable movement allowing moisture ingress. Earth grids The copper conductor and connections used for earth grids can deteriorate as a result of acids in the soil and they can also be damaged by heavy vehicles or digging. It is necessary to regularly test the earth grid to determine the condition and carry out essential repairs before the safety performance is compromised. Outdoor Junction Boxes Five ODJBs have been replaced due to condition in the last five years, and a recent enquiry found there are a small number of junction boxes in poor condition that are likely to require replacement during RCP2. The ODJB replacement programme is described in subsection Maintenance Requirements This subsection describes the maintenance requirements of the fleets of AC substations other primary assets. These requirements have informed the maintenance strategies (section 4.4). The most common types of maintenance carried out on ACS Other assets are: preventive maintenance, including: - condition assessments - servicing Transpower New Zealand Limited All rights reserved. Page 26 of 60

30 corrective maintenance, including: - repairs - fault response maintenance projects. ACS Other Primary Equipment Maintenance projects typically consist of relatively high-value planned repairs or replacements of components of larger assets. Maintenance projects would not be expected to increase the original design life of the larger assets. Maintenance jobs are typically run as a project where there are operational and financial efficiencies from doing so. The Maintenance Lifecycle Strategy provides further details on the above maintenance works. We undertake regular condition assessments on the ACS Other asset fleet. Assets such as instrument transformers, disconnectors and surge arresters are normally grouped around a major item such as a power transformer or capacitor bank. Maintenance on any equipment associated with one of these items will involve an outage of the whole group and maintenance is usually carried out on all associated equipment at the same time. Instrument transformers A 2009 CIGRE survey of 12 Australian and New Zealand transmission companies identified that the most common causes of failure of instrument transformers can be attributed to ageing, moisture ingress or oil contamination. We use inspections of external condition, typically scheduled at 4-yearly intervals, to identify any evidence of deterioration. Disconnectors and earth switches Disconnectors and earth switches are typically operated only rarely, and will at most be operated only a few times a year. Some have a tendency to become difficult to operate, due to infrequent use and degradation of lubricants as a result of exposure to the environment. The main problems to be addressed by routine maintenance are poor contact alignment, loss of contact spring pressure and corrosion of the contact braids. Gantry-mounted disconnectors and earth switches are particularly difficult to align because of the lengthy control rods and multiple linkages. Shaking due to seismic events may also cause the equipment to go out of alignment. Poor contact alignment will cause overheating or damage of the contacts. Infrared thermography is used as the main means to identify overheating contacts. For some disconnectors, correct alignment in the closed state can be verified from ground level by inspecting match marks. Outdoor busbar systems Most 50 kv 110 kv substations have galvanised steel lattice structures. Many older structures at stations near the coast and in industrial and geothermal areas require corrosion repairs and painting to preserve and extend their life. Lattice structures also require periodic tightening of bolts, and programmes of work for replacement of corroded bolts. Other stations have concrete bus support posts, and at some sites these posts show signs of cracking and spalling. As the condition of bus posts deteriorate, the bus system will become increasingly at risk, and as the posts continue to age the problem will become more serious. Transpower New Zealand Limited All rights reserved. Page 27 of 60

31 This has the potential to compromise the integrity of the bus system, and create safety hazards for personnel in the vicinity. Deterioration of support posts must be addressed by repairing or replacing ageing bus posts. There has been an increasing need for remedial works, life extension and partial replacement of bus systems as they age. This is expected to continue over the next 10 years Interaction with Other Assets The ancillary equipment at AC substations supports the major equipment such as circuit breakers, indoor switchgear, power transformers, reactive power, secondary systems, and substation management systems. Disconnectors and earth switches have an important relationship as they are usually mounted on a common stand and operated together for isolation and earthing purposes. Disconnectors can sometimes be the limiting factor on the rating of a complete branch. In these cases, the rating of the whole branch can be increased by uprating or replacing the disconnectors. In some instances, it has been possible to uprate a disconnector using reference to updated type tests provided by the original manufacturer. In other cases, the head gear of the disconnector has been replaced to provide a higher rating. The level of uprating that can be achieved is limited by the components (such as contacts, and flexible braids) that can be fitted, and the economics of the uprating. We have installed disconnecting circuit breakers in special situations. The disconnecting circuit breaker removes the need for traditional disconnector and their associated maintenance interval period of four years. The disconnecting circuit breaker has a maintenance interval period of eight years (which is the typical maintenance period for circuit breakers). The introduction of these disconnecting circuit breakers will reduce the need for planned outages for disconnector maintenance, and also rationalise a few of the 110 kv disconnector and earth switch fleet. 9 Our integrated works planning (IWP) process allows for coordination of works to minimise disruption and cost. Works on ACS Other assets will be coordinated with works on the main types of primary AC station equipment (such as transformers). In particular, work on buses and structures can usually be coordinated with work on other primary equipment Emerging Technologies Continuous improvements are being made in the technology of electricity transmission equipment, which provide opportunities to improve service to customers. To capture the opportunities without accepting undue risk, we undertake a conservative approach to new technology by developing a thorough understanding of the technology, including its benefits and risks, and testing the technology on the Grid. The main emerging technologies in the ACS Other fleet are discussed below. Optical instrument transformers Optical instrument transformers are slowly being adopted by overseas transmission utilities. The units are very accurate and have a much expanded current/voltage range so that one device may be used for several standard ratings. The disadvantage is that they are not 9 This is detailed in the ACS Outdoor Circuit Breakers Fleet Strategy. Transpower New Zealand Limited All rights reserved. Page 28 of 60

32 compatible with our standard protection and instrumentation; so special equipment has to be purchased to be used with them. We are trialling a set of 110 kv optical instrument transformers as an alternative to the present wound instrument transformers. Subject to proven reliability and accuracy, they will be introduced progressively across the transmission system. Compact integrated switchgear We are exploring and developing the potential for the use of compact integrated switchgear to eliminate the requirement for outdoor, air-insulated disconnectors and earth switches. Local service supply The new LVAC design standard advocates the use of power VTs as an alternative to local service transformers for an emergency power supply. 2.3 Asset Performance This section describes the historic reliability performance of the ACS Other assets together with a summary of key identified risks and issues Safety and Environmental Performance Vertically stacked double busbar systems Work being carried out above live equipment in vertically stacked double busbar systems has caused serious safety hazards and loss of supply events when tools and equipment have been dropped onto the bus below. One such event occurred at Wilton Substation in April We now prohibit work above live buses due to the associated safety hazards. Instrument transformer explosive failures We have had previous experience of violent failures of instrument transformers. These violent failures are now rare, but some previous failures have led to explosions, with porcelain projectiles travelling considerable distances across the switchyard and damaging other equipment Reliability Achieving an appropriate level of reliability for our asset fleets is a key objective for us, as it directly affects the services received by customers. Reliability is measured primarily by the frequency and length of outages. Instrument transformers Major failures Major failures are those that cause prolonged outages, result in significant damage to other equipment, or create serious safety risks. Major failures of 110 kv VTs occurred in 2003 and 2006, involving two different types. In the first case, the failure caused significant collateral damage. Investigation of both failures led to the identification of poor batches of VTs that were subsequently completely replaced, as high priority work. Transpower New Zealand Limited All rights reserved. Page 29 of 60

33 Forced and fault outages ACS Other Primary Equipment Over the past 7 years, on average we have had five instrument transformer forced or fault outages each year. Figure 8 shows the historic performance of instrument transformers. INSTRUMENT TRANSFORMERS - FORCED AND FAULT OUTAGES ENVIRONMENTAL FAULTY CONNECTIONS FAULTY/DETERIORATED OTHER 2006/07 07/08 08/09 09/10 10/11 11/12 12/13 Figure 8: Instrument Transformers: Forced and Fault Outages We are seeking to improve the reliability of instrument transformers with a replacement programme during RCP2, as described in subsection Disconnectors and earth switches Figure 9 shows the historic number of forced and fault outages for disconnectors. DISCONNECTOR AND EARTHSWITCHES - FORCED AND FAULT OUTAGES EQUIPMENT FAILURE OTHER /04 04/05 06/07 08/09 10/11 Figure 9: Disconnectors - Forced and Fault Outages The 2- yearly international ITOMS benchmarking process shows that we have a high rate of forced and fault outages of disconnectors compared with our international peers. 10 Figure 10 is taken from the ITOMS 2011 report and shows composite service level and costs 10 International Transmission Operations & Maintenance Study (ITOMS) is an international benchmarking study, comparing performance and maintenance cost between transmission utilities from North America, Europe, Asia and Australasia. Transpower New Zealand Limited All rights reserved. Page 30 of 60

34 for disconnectors. We are represented by the S marker, while the others represent overseas transmission networks. Figure 10: ITOMS Benchmarking Round - Disconnectors The benchmark results show that our disconnector and earth switch performance is significantly worse than our peers across all voltage classes. Our rate of forced and fault outage is approximately 8 times higher than the best ITOMS performer and 5 times higher than the average. The main cause of the poor performance is the vulnerability of much of our fleet to contacts not closing fully, or not remaining fully closed, as a consequence of mal-alignment of the mechanism. Further discussion on the high rate of forced and fault outages of disconnectors is included in subsection However, it should be noted that performance in the ITOMS benchmark surveys is not an accurate indication of the effect of disconnector performance on service to customers. Most forced outages of disconnectors do not result in an immediate loss of service to connected customers. Further, most of these forced outages are of relatively short duration. However, in a few severe cases, a contact meltdown has occurred, requiring extensive remedial work. Other equipment NERs NERs in general have not caused a forced outage or safety incident. There have been incidents where a transformer tripping/incident has caused the transformer and the NER to fail. Such incidences would be captured as a transformer failure and are shown in the power Transpower New Zealand Limited All rights reserved. Page 31 of 60

35 transformer strategy. There was one incident where a NER thermometer operated incorrectly, causing a forced outage of the associated power transformer Risks and Issues This subsection briefly discusses the most significant risks and issues facing the asset management of the ACS Other fleet, including the drivers and causes of the risks as well as the potential outcomes. Risk management for older instrument transformers The recent performance of instrument transformers has been good, but we know from experience here and elsewhere that instrument transformers can fail explosively, with severe consequences. There are large populations of some types of instrument transformers in service, and by the end of the RCP2 period some of these populations will have an average age greater than 40 years. One example is the ASEA 220 kv CT- type IMBD and IMBE. By the end of the RCP2 period, if there are no planned replacements, 245 of these CTs will be more than 40 years old. We aim to keep the risk of major failures as low as possible, because of the safety and reliability consequences of major failures. However, our standard inspections and tests do not provide detailed insights into internal condition. Modern instrument transformers are hermetically sealed, and we do not undertake routine diagnostic oil sampling, because we consider that the risk involved in undertaking such sampling outweighs the likely benefits. There is a risk that because of the limitations of routine condition assessment, a serious and unexpected mode of failure of one of these of older instrument transformers may emerge. This would lead to the need for urgent action to mitigate safety and reliability risks, across a significant population. A strategy to manage this risk is outlined in section 4.4.1, involving proactive replacement and detailed internal condition assessments of a small sample of instrument transformers from larger populations of ageing instrument transformers. Non-standard instrument transformers A number of older instrument transformers, manufactured before the 1970s, when the current standards were introduced, have ratios and classes that differ from the present standards. As described in subsection 4.1.2, this factor will be considered in the planning to replace the instrument transformers. Diversity of disconnector and earth switches Diversity is a significant issue for the fleet of disconnectors/earth switches because there are approximately 126 different models in service. This fleet diversity leads to significant complexity and cost in the work required to: establish and maintain basic asset information, drawings and records develop, implement and improve maintenance procedures assess and manage spares requirements undertake condition assessment Transpower New Zealand Limited All rights reserved. Page 32 of 60

36 develop asset health models develop asset management strategies forecast future expenditure requirements. ACS Other Primary Equipment The diversity of the disconnectors and earth switches will reduce somewhat during RCP2, as we plan to totally replace some models that have small individual populations. The replacement programme is described in subsection Asset knowledge and condition assessment of disconnectors The basic data and supporting information held about disconnectors requires improvement. There are inconsistencies in some of the basic data, and benefits could be obtained by formally identifying families of similar models of disconnectors. Supporting information for the various families of disconnectors requires some improvement, and this information needs to be published to make it more readily available to service providers. We have found that the current condition assessment process for disconnectors does not deliver a sufficiently robust indication of condition. There are some inadequacies in the design of the condition assessment framework, including the lack of a guide to ensure consistent scoring of condition. We have begun to implement significant improvements to condition assessment processes, including the provision of photographic guides to ensure a more comprehensive and consistent approach to condition assessment. Disconnectors and earth switches assembled on site Our standard practice is to procure disconnectors and earth switches that are shipped from the manufacturer as a packed set of components. We normally procure the support insulators separately. The complete disconnector and earth switch is then assembled on its support insulators at site, usually without the presence of a representative of the original manufacturer. Considerable care is required in installing and aligning the drive mechanisms to ensure satisfactory operation. Vulnerability of disconnectors to mal-alignment The main cause of the high rate of forced outages of disconnectors is the vulnerability of much of our fleet to contacts not closing fully, or not remaining fully closed, as a consequence of mal-alignment of the mechanism. Disconnectors are typically forced out of service following inspections where it is identified that a disconnector is not fully closed, or where overheating contacts are identified during infrared thermography surveys at substations. In a few severe cases, a contact meltdown has occurred. The vulnerability to mal-alignment is a problem that affects most of the disconnectors from a single manufacturer. Given that the majority of the fleet is from this single manufacturer, this vulnerability has major consequences for reliability of the fleet as a whole. Significant attention has been given recently to lifting the competency of the field workforce in achieving satisfactory alignment. Further details of the training and competency initiative are given in subsection Improvements in performance are expected over the next few years. Transpower New Zealand Limited All rights reserved. Page 33 of 60

37 Lack of disconnector and earth switch type test records ACS Other Primary Equipment Type test certificates for disconnectors and earth switches provide proof of the load and fault current ratings of the equipment, and are required when determining operational ratings for emergency loading or changes in operational conditions. A proportion of our disconnector and earth switch fleet (approximately 6%) have inaccurate or no records of type test results. Many of the disconnectors also do not have a nameplate and their formal ratings are unknown. This makes it hard to determine whether the units are sufficiently rated for the branch or not and whether uprating is required. To temporarily alleviate the issue, we have assigned these units with ratings based on the type of contacts and the type of disconnector/earth switch. Some units lacking a formal rating supported by type tests have been prioritised for replacement in the RCP2 (see subsection 4.1.2). Busbar designs Older busbar systems were originally designed for use with dead tank bulk oil circuit breakers and typically have lower busbar heights. This makes it difficult to retrofit the currently preferred live tank sulphur hexafluoride (SF 6 ) circuit breakers because of maintenance clearance requirements. The older busbar systems also have no provision for bus section breakers, which are now required at many existing sites due to increased expectations for system security and increasing loads. Vertically stacked double busbar systems are being removed from the system. These systems are considered unsafe as they may require maintenance work to be performed above or below live equipment. The consequences of an accident occurring in this situation can be high, with the potential to cause a fatality. To minimise safety hazards, work above live busbars has been prohibited. During RCP2 we will put a suitable standardised busbar design in place that will be used for new and replacement busbars. The standardised design will also be used as far as practicable for busbar refurbishments. During RCP2 we will undertake a number of refurbishments, as described in subsection In addition, a number of 33 kv busbar systems will be removed and replaced with indoor switchgear (refer to the Outdoor 33 kv Switchyards Fleet Strategy). Application of portable earths in outdoor structures Maintenance work in outdoor structures requires the application of portable earths. There are significant risks in applying portable earths in outdoor switchyards. Portable earthing equipment is long and heavy, and this makes it difficult to handle. Manoeuvring portable earthing equipment in close proximity to live equipment can present a significant hazard. The risks associated with handling portable earths in the tight clearances typically found in outdoor, medium-voltage switchyards will gradually reduce over time, as more of these switchyards are converted to indoor switchboards. Gap-type surge arresters A number of gap-type surge arresters remain in service, but there are concerns about their ability to safely discharge higher impulse currents. In addition, if they operate, they create an earth fault on the system that can be the trigger for a major outage. Gap-type surge arresters have proven to be unreliable and can cause outages without a lightning strike. Rod gaps are an old and unreliable technology and have caused a number of outages. We are Transpower New Zealand Limited All rights reserved. Page 34 of 60

38 continuing a programme to replace the gap-type surge arresters, as described in subsection Overhead earth wire lightning protection Overhead earthwires provide lightning protection coverage via conductors that are strung between structures within substations and, in some cases, above live equipment. Mechanical failure of a critical earthwire or its attachment point hardware can cause it to fall onto live equipment, damaging the equipment and creating a fault. This can cause significant network outages and major damage to equipment that is costly to repair. System outages can be particularly large if a failed earthwire causes a fault on a bus. Local service system reliability Local service power provides important services at substations. Loss of local service power supply at a substation, even for a short period, can lead to immediate consequences for the operation and capability of some major equipment such as synchronous condensers, Static Var Compensators and power transformers. This equipment may shut down following loss of local service power, or operate at a restricted rating. Loss of the local service alternating current supply for an extended period will lead to discharge of critical station batteries supplying the control and protection system. This can ultimately lead to the complete failure of all power system control and protection at the site, with potentially widespread consequences in the event of a power system fault. Large sites generally have two independent sources of local service power, and there are backup emergency generators at a few sites. In some cases, specific provision has been made to rapidly connect mobile generators in the event of a local service failure. Local service switchboards can be a point of common mode failure, even if the site has more than one source of infeed. As outlined in section 2.2.3, the local service equipment at some older sites is in deteriorated condition, and often no longer fully meets current requirements. In particular, at some of our largest sites, the local service equipment does not meet current expectations for security and reliability. Some local service installations are located in cable basements, and lack adequate physical segregation from other services. Subsection describes the replacements that will be undertaken in RCP2 to address this issue. Transpower New Zealand Limited All rights reserved. Page 35 of 60

39 3 OBJECTIVES Chapter 3 sets out asset management related objectives for the ACS Other fleets. As described in section 1.5, these objectives have been aligned with our corporate management objectives, and higher-level asset management objectives and targets as set out in the Asset Management Strategy. Our overarching vision for our ACS Other fleets is to ensure that it operates safely and reliably over its expected life. Specific objectives have been defined in the following five areas: Safety Service performance Cost performance New Zealand communities Asset management capability. These objectives are set out below, while the strategies to achieve them are discussed in chapter Safety We are committed to becoming a leader in safety by achieving injury-free workplaces for our employees and to mitigating risks to the general public. Safety is a fundamental organisational value and we consider that all incidents are preventable. Safety Objectives for ACS Other Fleets - Zero fatalities and injuries while maintaining, repairing or installing other station equipment. - Minimise risk of injuries from explosions of instrument transformers. - Appropriately rated disconnectors and earth switches are provided to enable safe operation of Grid assets. - Earth grid design and condition ensures that step and touch potentials are kept within safe limits. 3.2 Service Performance Ensuring appropriate levels of service performance is a key underlying objective. The overall service performance objectives for the Grid in terms of Grid Performance (reliability) and Asset Performance (availability) are set out in the Asset Management Strategy. Grid performance objectives state that a set of measures are to be met for Grid Exit Points (GXPs) based on the criticality of the connected load. In addition, asset performance objectives linked to system availability have been defined. These high-level objectives are supported by a number of fleet specific objectives, and we will work towards these being formally linked in the future. Transpower New Zealand Limited All rights reserved. Page 36 of 60

40 Service Performance Objectives for ACS Other Fleets - 10-year rolling average for major failures of instrument transformers remains less than 0.05% each year. It is currently less than 0.05% each year year rolling average rate of instrument transformer forced outages to be less than 5 events per annum. - Reduce the number of disconnector/earth switch forced outages to 50% of the 2011 level by Design and condition of local service systems at key substations is commensurate with the risks associated with sustained loss of 400 V supply. 3.3 Cost Performance Effective asset management requires optimising lifecycle asset costs while managing risks and maintaining performance. We are committed to implementing systems and decisionmaking processes that allow us to effectively manage the lifecycle costs of our assets. Cost Performance Objectives for ACS Other Fleets - Minimise whole-of-life cost, including: o improved procurement processes, considering maintenance costs and capital costs o extended warranties in place for new equipment o apply lifecycle cost analysis to the decisions between replacement and refurbishment of disconnectors. - Further reduce model diversity to help reduce maintenance costs. 3.4 New Zealand Communities Asset management activities associated with the ACS Other fleets have the potential to impact on both the environment and on the day-to-day lives of various stakeholders. Relationships with landowners and communities are of great importance to us and we are committed to using asset management approaches that protect the natural environment. New Zealand Communities Objectives for ACS Other Fleets - Oil containment facilities minimise spills of oil to the environment. - Minimise risk of damage to third party property from instrument transformer explosions. 3.5 Asset Management Capability We aim to be recognised as a leading asset management company. To achieve this, we have set out a number of maturity and capability related objectives. These objectives have been grouped under a number of processes and disciplines that include: Transpower New Zealand Limited All rights reserved. Page 37 of 60

41 Risk management Asset Knowledge Training and Competency Continual Improvement and Innovation. ACS Other Primary Equipment The rest of this section discusses objectives in these areas relevant to the ACS Other fleets Risk Management Understanding and managing asset-related risk is essential to successful asset management. We currently use asset criticality and asset health as a proxy for a fully modelled asset risk approach. Asset criticality is a key element of many asset management systems. We are currently at an early stage of developing and implementing the framework as we work towards formal and consistent integration of asset criticality into the asset management system. We have commenced this by prioritising fleet replacement expenditure programmes, based on the criticality framework. Risk Management Objectives for ACS Other Fleets - Develop asset health models for instrument transformers and disconnectors. - Apply asset criticality to the prioritisation of capital expenditure Asset Knowledge We are committed to ensuring that our asset knowledge standards are well defined to ensure good asset management decisions. Relevant asset knowledge comes from a variety of sources including experience from assets on the Grid and information from the manufacturers. This asset knowledge must be captured and recorded in such a way that it can be conveniently accessed. Asset Knowledge Objectives for ACS Other Fleets - Revise condition assessment regime for outdoor structures and disconnectors to align with the steel and insulator condition scoring system used for transmission lines assets. - Establish an appropriate asset condition assessment process for: o o local service systems ODJBs. - Share failure knowledge with other network operators Training and Competency We are committed to developing and retaining the right mix of talented, competent and motivated staff to improve our asset management capability. Transpower New Zealand Limited All rights reserved. Page 38 of 60

42 Training and Competency Objectives for ACS Other Fleets ACS Other Primary Equipment - Ensure continued competence of the field workforce in the setup and alignment of disconnectors. - Ensure appropriate training is available for all new technologies Continual Improvement and Innovation Continual improvement and innovation are important aspects of asset management. A large source of continual improvement initiatives will be ongoing learning from our asset management experience. Continual Improvement and Innovation Objective for ACS Other Fleets - Continue to explore the potential of non-conventional instrument transformers. Transpower New Zealand Limited All rights reserved. Page 39 of 60

43 4 STRATEGIES Chapter 4 sets out our fleet specific strategies for the management of the fleet of ACS Other assets. These strategies are designed to support the achievement of the objectives in chapter 3 and reflect the characteristics, issues and risks identified in chapter 2. The strategies are aligned with our lifecycle strategies below and the chapter has been drafted to be read in conjunction with them. Planning Lifecycle Strategy Delivery Lifecycle Strategy Operations Lifecycle Strategy Maintenance Lifecycle Strategy Disposal Lifecycle Strategy This chapter also discusses personnel and service provider capability related strategies which cover asset knowledge, training and competence. Scope of strategies The strategies focus on expenditure that is planned to occur over the RCP2 period ( ), but also include expenditure from 1 July 2013 to the start of the RCP2 period and some expenditure after the RCP2 period (where relevant). Capex planned for the RCP2 period is covered by the strategies in sections 4.1 and 4.2, and opex is covered by the strategies in sections 4.3 to 4.6. The majority of the capex consists of replacements, particularly instrument transformers and disconnectors and earth switches, as described in subsection Planning This section describes our strategies for planning activities for the ACS Other fleet. Planning activities Planning activities are primarily concerned with identifying the need to make capital investments in the asset fleet. The main types of investment considered for this fleet are enhancement and development, replacement and refurbishment. We support these activities through a number of processes, including: Integrated Works Planning (IWP) cost estimation. The planning lifecycle strategies for the ACS Other fleet are described in the subsections below. Capital investment drivers Categories of capital investment generally have specific drivers or triggers that are derived from the state of the overall system or of individual assets. These drivers include demand growth, safety, compliance with Grid reliability standards and failure risk (indicated by asset criticality and condition). Transpower New Zealand Limited All rights reserved. Page 40 of 60

44 Specific examples that drive capital investment in ACS Other assets include: ACS Other Primary Equipment modifications or replacements of bus structures to improve safety new substation developments or expansions, driven by demand replacements for deteriorated or, in rare cases, failed assets. The strategies below consider the long-term implications for these drivers as we extend our planning horizon as part of our programme of asset management improvement Enhancement and Development This subsection describes enhancement and development investments for the ASC Other fleet. Enhancement and development investments are undertaken in response to a number of drivers including supply and demand forecasts, and the need to maintain appropriate levels of availability. The most important driver for investments in the fleet of ACS Other assets is the need to facilitate new or uprated AC substation assets. Islington local service system upgrade Complete the upgrade of the Islington low-voltage supply system, which commenced in RCP1. We have carried out studies assessing the potential for high impact, low probability (HILP) risks at Islington Substation. This site is particularly critical, with the potential HILP events to cause major impacts on the reliability of supply to the upper half of the South Island. The risk studies have indicated that the local service system is an area of significant risk for the Islington Substation, particularly in terms of fire risk. To address this, we have commenced a project in RCP1 to remove the main LVAC supply system from the cable basement and install it adjacent to the main building where there will be less fire risk. The essential and non-essential switchboards will be separated to further reduce risk. We will also improve the reliability of the system by replacing the aged and non-standard LVAC local service transformers with four 33 kv/415 V transformers to supply the Islington Substation and the National Grid Operating Centre (NGOC) building. Based on the cost estimation of the detailed design, we estimate that the portion of the project remaining in RCP2 will cost approximately $3m Replacement and Refurbishment Replacement is expenditure to replace substantially all of an asset. Refurbishment is expenditure on an asset that creates a material extension to the end of life of the asset. It does not improve its attributes. This is distinct from maintenance work, which is carried out to ensure that an asset is able to perform its designated function for its normal life expectancy. Specific interventions have been defined for the fleet of ACS Other equipment based on their condition and informed by their relative criticality. These interventions and their rationale are set out below. Transpower New Zealand Limited All rights reserved. Page 41 of 60

45 Instrument transformers ACS Other Primary Equipment Figure 11 provides an overview of the process used to identify instrument transformers for replacement. The specific replacement strategy for the fleet of instrument transformers is described in the diagram. PHASE 1 Initial Drivers PHASE 2 Technical Analysis Asset Diagnostics (MMS Data) - Visual inspection - Insulation tests - Operational tests - Condition Assessment data Instrument transformer has reached the end of its financial or engineering life Initiated at years Performance (SFIRs) - Operational Safety - Operation - Failure history (including overseas experience Instrument transformer has an emerging or generic defect (CA data, SFIRs) Initiated on defect Risk - Operational safety risk based on diagnostic tests - Impact of failure - Site criticality - Public risk Spares availability and condition (Inventory) - Replacement spares - Component spares Population size Technology Environment - Oil REPLACE Replace in 1-5 years ONGOING MONITORING Re-evaluate in 1-5 years Figure 11: Instrument Transformer Replacement Assessment Instrument transformer replacement programme Identify and replace ageing and poor condition instrument transformers. As outlined in subsection 2.3.3, there is a risk that, because of the limitations of routine condition assessment, a serious and unexpected mode of failure may emerge with some of the older instrument transformers. The size of some of these older populations and the severe consequences of any major failure indicate that a conservative asset management approach is required. A small number of units from larger populations of ageing instrument transformers will be treated as samples and will be replaced to allow detailed internal condition assessments, as outlined in subsection Poor condition transformers are classified as those that meet the following criteria: condition assessment inspection and test and/or service history show insulation or other major component deterioration beyond specified limits service experience or reports from other utilities indicate a generic problem leading to the risk of catastrophic failure of a particular make or model Transpower New Zealand Limited All rights reserved. Page 42 of 60

46 ACS Other Primary Equipment the current or fault rating is not adequate for the required service duty (where applicable). We have a number of non-standard instrument transformers, which are pre-1970s units that do not meet the current ratio or class standards together with current requirements for accuracy and seismic strength. When non-standard ratio instrument transformers fail, or when an upgrade opportunity arises, they will be replaced with standard assets. The replacement of a non-standard ratio instrument transformer may necessitate other project works, including protection setting changes, recalibration of revenue metering and replacement of differential protection CTs. Based on the current condition and status of instrument transformers, we estimate that 496 instrument transformers will require replacement over the RCP2 period as summarised in Table 13. Type Forecast RCP2 Replacements CT 339 NCT 4 CVT 132 VT 21 Table 13: Instrument Transformer Replacements 11 The overall rate of replacement planned during the 5-year RCP2 period is an average of 2% of the fleet each year. The cost of the instrument transformer replacements has been forecast for the RCP2 period using volumetric forecasting, based on the estimated unit costs provided in Table Type kv 110 kv 220 kv CT N/A $103,000 $104,000 CVT N/A N/A $86,000 VT $59,000 $63,000 N/A NCT N/A $15,000 $21,000 Table 14: Estimated Instrument Transformer Replacement Costs for each Three Phase Set 12 The forecast expenditure for the RCP2 period for instrument transformer replacements is $15.8m. Disconnectors and earth switches As outlined in subsection 2.1.2, our fleet of almost 4,000 disconnectors and earth switches is highly diverse, with a wide range of makes and models. In addition, a relatively large number of disconnectors and earth switches will reach the end of their nominal life expectancy by the beginning of RCP3. Finally, as discussed in 2.3.2, the reliability is poor, with a rate of forced and fault outage that is the worst of all ITOMS benchmark study participants These are the number of replacement projects where each project will replace three freestanding instrument transformers. These costs refer to the cost for each three phase set, which each include three individual instrument transformers. Transpower New Zealand Limited All rights reserved. Page 43 of 60

47 The main cause of the poor performance is the vulnerability of much of our fleet to contacts not closing fully, or not remaining fully closed, as a consequence of mal-alignment of the mechanism. We are working to improve the performance of disconnectors by improving the training of our service providers in achieving optimum alignment, as outlined in subsection We also recognise a need to improve asset knowledge and condition assessment processes, as outlined below and in subsection Our overall asset management approach for disconnectors is not yet fully mature, and the improvements outlined above are key to lifting performance over the longer term. Given the preceding background, the following section outlines our approach to planning the replacement and refurbishment of disconnectors and earth switches. Disconnectors and earth switches replacement/refurbishment programme Replace or refurbish disconnectors and earth switches when they reach replacement criteria. Major interventions for disconnectors and earth switches can be either replacement or refurbishment. These two interventions are outlined below. Replacement of disconnectors and earth switches As outlined above, one of our key initiatives to improve performance is the ongoing programme of training of service providers to ensure that disconnectors are correctly aligned. However, our strategy for improving performance also includes total replacement of some of the worst performing models. We also seek to reduce asset management complexity by reducing the diversity of the fleet. We will review all the populations of disconnectors where there are fewer than 20 of a broadly similar type in service, and prioritise these for replacement where practical. Disconnectors and earth switches will be considered for replacement based on one or more of the following criteria: presence of an emerging or generic defect based on condition data and/or performance records, where a maintenance or refurbishment solution is not costeffective, or cannot effectively resolve the root cause essential spares are no longer available or cannot be economically manufactured there is no traceable type test certificate to provide support for the rating of the asset operational requirements for the site are for remote control of the disconnnector, but it is not possible to motorise the existing equipment the model is of a type with a population of 20 or less, and is more than 20 years old. Refurbishment of disconnectors and earth switches For some disconnectors/earth switches it is possible to undertake refurbishment to extend the life of the asset, as an alternative to replacement. Refurbishment typically involves removing part or the entire unit for overhauling in a workshop. If there is a reasonably large population of identical equipment, refurbishment can be implemented as an exchange Transpower New Zealand Limited All rights reserved. Page 44 of 60

48 programme, where previously refurbished equipment is exchanged on site, to minimise outage time. A disconnector/earth switch will be considered for refurbishment when the following apply: the mechanical and electrical properties of the refurbished asset meet, or exceed, that of the original asset parts are available to refurbish a disconnector/earth switch that would otherwise be replaced cost of refurbishment or repair is less than 80% of a new disconnector/earth switch there is an ongoing need for that type of disconnector/earth switch and it is still required in the system following bus rationalisation. A number of defective models would not be considered for refurbishment as this would not remove the associated design defects present in the models. RCP2 plan We have recognised that the asset management information we currently have available about disconnectors and earth switches is not of sufficient quality and consistency to support fully robust and consistent decision making about priorities for replacement and refurbishment. Improvements in asset condition information and in data quality are required, and initiatives to achieve these improvements have commenced. This will enable a more systematic approach to replacement and refurbishment decisions, and the development of an asset health model for long-range forecasting. We also require improved understanding of the typical costs for refurbishment of different types of disconnectors from a variety of states of as-found condition. Improved condition assessment data, together with these improvements in cost estimation can then be used as inputs to a more robust decision making framework. Following from the above, the present RCP2 plan includes a compilation of disconnector replacement projects, but these represents a provision rather than a firm plan for specific assets. The total number of disconnectors and earth switches forecast to require replacement or refurbishment over RCP2 is 173, broken down by voltage, as noted in Table kv 110 kv 220 kv Disconnectors and earth switches Table 15: Forecast RCP2 Replacements and Refurbishments of Disconnectors and Earth Switches The rate of replacement planned during the 5-year RCP2 period is an average of approximately 1% of the fleet each year. Cost estimates for each disconnector or earth switch replacement have been completed as volumetric projects using US Cost estimates. The unit rates used are based on recent replacement project costs. Based on the above volumes and costs, the total expenditure forecast for the RCP2 period for disconnector and earth switch replacements is $12.4m. The improvements in asset management outlined above are expected to lead to significant re-prioritising of work on disconnectors and earth switches, and the allocation of funds Transpower New Zealand Limited All rights reserved. Page 45 of 60

49 towards refurbishment of many models, rather than replacement. However, the level of expenditure proposed for the period is considered to be a minimum that will maintain the fleet in an acceptable condition and enable the necessary improvements in performance. Other equipment Bus system refurbishments Replace or refurbish busbar systems at 50 kv and above that present greater safety or performance risks than modern designs or impose operational constraints. There are still some vertically stacked double busbar systems in service that present greater safety risks than modern designs. In addition, the configuration of some structures leads to significant operational and maintenance constraints. We have an ongoing programme to replace or refurbish these systems to ensure that the buses and structures provide the required physical clearances for contractors to carry out maintenance work safely and provide appropriate operational flexibility. Low-level structure designs are preferred as a replacement solution. However, it is often not practical to replace the older lattice types with low-level structures, particularly in cramped sites, because they have a much larger footprint than the original lattice type. Busbars and structures will also be brought to a state where they meet the latest seismic standards. Improvement in the seismic capability of the buses and structures will make the network more resilient to earthquake events, and reduce the safety hazard to personnel during an earthquake. During RCP2, we will complete the last of five bus projects that commenced during RCP1 at Timaru, Wilton, Hawera and Waihou. In addition, approximately $5.5m will be spent on a major project to replace the 110 kv structure and buswork at Kinleith Substation. Busbar reinsulation and refurbishment projects will be completed at Maraetai and Henderson. The forecast expenditure for bus replacements and refurbishments during the RCP2 period is $11.6m. The cost of each project has been estimated individually, and further information on the cost estimation method is provided in subsection Surge arrester replacements Replace all gap-type surge arresters. As discussed in subsection 2.3.3, we have significant concerns about the reliability of the few remaining older gap-type surge arresters. During RCP2, we will continue the ongoing programme to replace these assets with modern gapless surge arresters. By the start of RCP2 we forecast that there will be two 110 kv gap-type surge arresters and four 220 kv gap-type surge arresters left, which will all be replaced during RCP2. Estimates of the cost for each replacement have been completed as volumetric projects using US Cost. The unit rates used are based on recent replacement project costs. 110 kv 220 kv Surge arresters $51,000 $54,000 Table 16: Estimated Costs for each Unit for Replacement Surge Arresters Transpower New Zealand Limited All rights reserved. Page 46 of 60

50 The total expenditure forecast for the RCP2 period for gap-type surge arrester replacements is approximately $320,000. Substation LVAC panel replacements Survey substation LVAC panels and undertake replacements based on condition criteria and install a main 400 V switchboard as required. A number of LVAC panels have problems with worn and deteriorated components. Many LVAC panels are of an age and condition where replacement is deemed necessary to ensure reliable operation. The current design standard specifies a main 400 V switchboard and a separate LVAC panel for essential supplies. At some small stations the LVAC panel and the switchboard are combined. In these cases, a new main 400 V switchboard will be installed when the LVAC panel is replaced. Based on a desktop study, we estimate that approximately 34 sites will require LVAC panel replacements. A system-wide survey is planned to confirm the condition assessment of all LVAC panels, and identify the detailed scope of work, before the programme commences. The forecast of expenditure during RCP2 is a volumetric forecast, which is described in subsection and based on the estimated unit costs noted in Table 17. Type Unit Cost LVAC panel $94,000 Panel and switchboard $120,000 Table 17: Estimated Unit Costs of LVAC Panel Replacements The overall forecast cost for the replacement of LVAC panels during RCP2, including installation of switchboards where required, is approximately $3.3m. Where feasible, the replacement of LVAC panels in poor condition will be coordinated with other major projects at the site, such as power transformer replacement, indoor switchboard replacement, or conversion of outdoor medium-voltage switchgear to indoor switchgear. In addition to the nationwide replacement of LVAC panels in poor condition, we plan to complete the Islington substation local service system upgrade project that began in RCP1, at an estimated cost of $3m during RCP2, as outlined in section above. Outdoor Junction Boxes Survey all ODJBs and replace units that meet replacement criteria. The aim of this strategy is to replace ODJBs that do not meet our maintenance, operational and standards requirements. The replacements are to be carried out as part of a larger project that replaces or upgrades the associated equipment, such as a power transformer, circuit breaker, and so on. However, any urgent replacements will be implemented as soon as possible. Criteria for the replacement of ODJBs may include: metalwork severely corroded Transpower New Zealand Limited All rights reserved. Page 47 of 60

51 inadequate structural design exposed live terminals and connections ACS Other Primary Equipment circuitry and equipment underrated for present fault and full load conditions congested insufficient space or clearances to install such items as additional relays, LV circuit breakers, switches, miniature circuit breakers, resistors and cables instrumentation, if fitted, operating incorrectly. Volumes and costs Further investigations will be required to confirm the number of ODJBs that need be replaced and establish priorities. This will include establishing a more robust condition assessment framework. However, our current volume forecast is that 37 ODJBs will be required to be replaced during RCP2. Based on an estimated average cost of $50,000 for each ODJB, the total cost for ODJB replacements is forecast to be $1.9m over RCP2. Substation lightning protection upgrade Upgrade the lightning protection system at substations where our standard is currently not being met. The purpose of this strategy is to ensure all existing lightning protection systems at our substations are adequate. Existing protection systems will be evaluated and where inadequacies are detected (such as excessive degradation), replacement of necessary parts of the system will be carried out. Earthwires used for lightning protection above 110 kv and 220 kv buses are, where practicable, to be removed and replaced with lightning masts. The investigation of lightning protection at substations will be prioritised by criticality of the substation/equipment and lightning intensity at each site, and a programme prepared to address identified deficiencies. At a few critical sites, we have undertaken specific projects to upgrade lightning protection. Our approach for implementing lightning protection upgrades at other sites is under review. In general, we will coordinate the review and upgrade of lightning protection with other major works at the site. We have not identified any specific lightning protection projects as being required for the RCP2 period, so have not forecasted a cost for this strategy Integrated Works Planning Our capital governance process IWP includes the creation of business cases that track capital projects through three approval gates. Works are optimised into groupings that produce more efficient and coordinated delivery programmes, reflect our site strategies, and minimise the number of outages and resources required. These processes ensure work is not undertaken on assets that are soon to be replaced or decommissioned. Ancillary equipment is normally grouped around a major item of equipment, and major works on any item of equipment within this group will necessitate an outage for the whole group. During an outage it is possible to carry out work on the major and ancillary equipment minimising the number and overall length of outages, the duplication of effort, and transport and operational costs. In particular, planned replacement, repair or Transpower New Zealand Limited All rights reserved. Page 48 of 60

52 refurbishment on ancillary equipment that falls within a 5-year window either side of a project to replace, repair, refurbish or maintain a major item of equipment, is to be included in the project on the major equipment Cost Estimation Cost estimation is a key stage of the capital investment process and forms a critical input into projects at various stages in the planning process. Further details on our cost estimation approach can be found in the Planning Lifecycle Strategy. Historically, cost estimates for the equipment in this fleet was developed using proprietary systems. This has now transitioned to a central cost estimation team, which uses the cost estimation tool Transpower Enterprise Estimation System (TEES). Approximately 50% of capital spending on disconnector and earth switch and instrument transformer replacements are the hardware cost. These are imported and thus exposed to exchange rate fluctuation. Scoping and cost estimation Scope and estimate project works to a P50 confidence level; that is, the estimate is based on a 50% probability that the cost will not be exceeded. Subsection provides details of the estimation approach used for replacement projects, including which are volumetric cost estimates and which are individual customised estimates. Volumetric works Disconnector, earth switch and instrument transformer replacements are examples of volumetric works as they are reasonably repetitive with largely similar scope. The key determinant of accurate cost estimates for volumetric capital projects is the effective feedback of cost out-turns from completed, equivalent replacement works. Volumetric estimates are determined using the TEES (US Cost) system. Tailored building blocks have been developed for assets based on actual cost out-turns from completed, equivalent works. This feedback-based process is used to derive average unit costs for future works. A volumetric approach to estimating costs for this equipment will help ensure works are scoped to achieve a P50 level of confidence, where P50 is an estimate with a 50% probability that the cost will not be exceeded. Assumptions made in using a volumetric costs methodology for the disconnector, earth switch and instrument transformer fleets include that: the volume of historic works is sufficiently large and a large number of equivalent projects will be undertaken in future cost building blocks based on historic out-turn costs capture the impact of past risks scope is reasonably well defined and reflect the predetermined list of standard building blocks in US Cost. Transpower New Zealand Limited All rights reserved. Page 49 of 60

53 4.2 Delivery ACS Other Primary Equipment Once the planning activities are completed, capex projects move into the delivery lifecycle. Delivery activities are described in detail in the Delivery Lifecycle Strategy. The following discussion focuses on delivery issues that are specific to the ACS Other fleet Design A number of design strategies have been developed for the ACS Other fleet. Busbar system standardisation Where practicable and economic, standardise busbar systems as they become due for replacement. This strategy aims to reduce the diversity within the fleets of busbars systems, to reduce the costs of engineering support, operation and maintenance. Busbars designed to current standards will also provide improvements on the safety of the older designs. As existing busbars are scheduled for replacement due to age, condition or other requirements, the option of rebuilding or replacement with current standard design will be carefully considered. Where practical and economic, replacement busbars will be built to conform to new standards. This strategy will: minimise fleet diversity and so support cost optimisation through a reduction in the cost of design, installation, operation, maintenance and spares enable the application of maintenance and repair procedures across a larger proportion of the fleet, and so reduce the knowledge and expertise required allow for a simpler inventory through enhanced interoperability and interchangeability of spare parts, to allow for improved management and deployment of spare parts from the inventory ensure new busbar systems meet modern safety standards. In addition, we will use the new standardised design as much as practicable for refurbishments. LVAC system standardisation Standardise the LVAC system when the LVAC switchboard is replaced for increased reliability and flexibility. This strategy aims to bring the LVAC system to current standards (which include requirements for alternate power sources). This allows for additional reliability and flexibility during periodic maintenance of the power sources. Transpower New Zealand Limited All rights reserved. Page 50 of 60

54 4.2.2 Procurement ACS Other Primary Equipment Our centralised group is tasked with providing procurement assistance for all services and assets. For more details of our general approach to procurement, see The Sourcing, Supply & Contracts Approach (2011) and the Delivery Lifecycle Strategy. We have developed the following specific procurement strategy for the ACS Other equipment fleet. Number of vendors Procure disconnectors, earth switches and instrument transformers from the minimum possible number of vendors commensurate with the need to manage supplier risk. We will also work to strengthen relationships with the limited group of vendors to ensure that the equipment meets specific quality requirements for New Zealand conditions. Ideally, at any one time, there will be only one period contract supplier for disconnectors, earth switches and instrument transformers for a particular voltage class. Limiting to one vendor enables standardisation and cost efficiencies in installation designs and in most aspects of lifecycle asset management. 4.3 Operation The Operation Lifecycle phase for asset management relates to planning and real-time functions. Operational activities undertaken are described in detail in the Operations Lifecycle Strategy. The following discussion focuses on operational issues that are specific to the ACS Other fleet Outage Planning Power system outages for preventive maintenance, corrective maintenance, and replacements must be planned to minimise disruption to customers. Grid operations identify requirements for outages and manage the planning of outages. A number of procedures carried out on the majority of the ACS Other asset portfolios cannot be carried out as live-line work. This means that an outage must be planned and managed in a way that creates a safe environment for employees and service providers to undertake the work, while minimising the disruption for customers. Consequently, the operation and maintenance of most of the ACS Other asset portfolios has to be coordinated with distribution and industrial customers. Contingency Planning Failure of the transmission service leads to an immediate impact on end consumers, and may result in disruption to economic and social activity. Some transmission asset failures can present serious safety hazards for employees and members of the public, or result in environmental damage. Therefore it is essential that we have plans in place for responding promptly and effectively to transmission system incidents and emergency situations. Transpower New Zealand Limited All rights reserved. Page 51 of 60

55 Contingency response resources ACS Other Primary Equipment Maintain sufficient emergency spares in place to enable rapid restoration of transmission service following ACS Other equipment failures. Contingency planning for instrument transformers, disconnector and earth switches and surge arrestors focuses on reviewing and maintaining the holdings of spares, and ensuring an adequate level of emergency preparedness. The spares include entire instrument transformers, surge arrestors and disconnectors and earth switches as well as spare components for disconnectors and earth switches. Currently, it is estimated to take a minimum of 28 weeks to purchase a new high-voltage outdoor instrument transformer. In the event of widespread catastrophic failures, all instrument transformers available in store, including project equipment, would be used until suitable permanent replacement equipment could be purchased. In these cases, the continued operation of the transmission systems takes precedence over new projects. It may be possible to remove in-service equipment from other sites to restore supply or security. We also have a longstanding arrangement with Australian transmission companies that provides a means of access to equipment and expertise in the event of an emergency. 4.4 Maintenance We and our service providers carry out ongoing works to maintain assets in an appropriate condition and to ensure that they operate as required. The maintenance undertaken seeks to proactively manage failure risk as well as responding to actual failures as these occur. We class maintenance tasks into the following categories: preventive maintenance, including: - condition assessments and patrols - prevent maintenance/servicing corrective maintenance, including: - fault response - repairs maintenance projects. The remainder of the section describes our maintenance activities and strategies relating to the ACS Other fleet Preventive Maintenance Preventive maintenance is work undertaken on a scheduled basis to ensure the continued safety and integrity of assets and to compile condition information for subsequent analysis and planning. Preventive maintenance is generally our most regular asset intervention, so it is important in terms of providing feedback of information into the overall asset management system. Being the most common physical interaction with assets, it is also a potential source of safety incidents and human error. The main activities undertaken are listed below. Transpower New Zealand Limited All rights reserved. Page 52 of 60

56 ACS Other Primary Equipment Inspections: non-intrusive checks to confirm safety and integrity of assets, assess fitness for service, and identify follow up work. Condition assessments: activities performed to monitor asset condition or predict the remaining life of the asset. Servicing: routine tasks performed on the asset to ensure asset condition is maintained at an acceptable level. We will implement the following preventive maintenance on the fleet of ACS Other assets in support of our objectives stated in chapter 3. Earth grid current injection tests Carry out current injection tests, including voltage gradient tests, on earth grids. We will carry out current injection tests on all earth grids, at a frequency of once every 15 years. The tests will include voltage gradient tests to identify step and touch potential risks. Any earth grid that fails the current injection and voltage gradient tests are to be addressed by full inspection followed by repair, extension, or replacement (as required). On the basis of the tests being carried out at each site every 15 years, we estimate that approximately 12 tests will be required each year over the RCP2 period. Instrument transformer pilot assessments Undertake pilot internal condition assessments of populations of older instrument transformers. There are large populations of some types of instrument transformers, and some of these populations have an average age greater than 40 years. The performance to date of these instrument transformers has been very good. Yet the standard inspections and tests do not provide detailed insights into internal condition. It is planned to undertake pilot condition assessments of a sample of instrument transformers from large populations, to assist in asset management decision making. The pilot condition assessments will include oil sampling. Tests may also include removal of the instrument transformer from site to a laboratory to undertake partial discharge testing, and potentially include dismantling for detailed internal inspection prior to disposal. Disconnector maintenance Undertake systematic changes to maintenance of disconnectors to improve condition assessment processes and reduce instances of forced outages caused by mal-alignment. As outlined in subsection 2.3.3, there are a range of issues associated with the asset management and maintenance of disconnectors. Systematic improvements are required to reduce the rate of forced and fault outage, and facilitate improved asset management decision making. Key initiatives already in progress include: Transpower New Zealand Limited All rights reserved. Page 53 of 60

57 ACS Other Primary Equipment development of Standard Maintenance Procedures that are specific to each make and model comprehensive review of the condition assessment process, including the provision of a photographic guide to enable more consistent assessment scoring training programmes for service providers to improve the level of skill and competence in the setup and alignment of disconnectors Corrective Maintenance Corrective maintenance includes unforeseen activities to restore an asset to service, make it safe or secure, prevent imminent failure and address defects. It includes the required followup action, even if this is scheduled some time after the initial need for action is identified. These jobs are identified as a result of a fault or in the course of preventive work such as inspections. Corrective works may be urgent and if not completed for a prolonged period may reduce network reliability. Corrective maintenance has historically been categorised as repairs and fault (response) activities. Repairs include the correction of defects identified during preventive maintenance and other additional predictive works driven by known model type issues and investigations. 13 Timely repairs reduce the risk of failure, improve redundancy and remove system constraints by maximising the availability of assets. Activities include: Fault restoration: unscheduled work in response to repair a fault in equipment that has safety, environmental or operational implications, including urgent dispatch to collect more information Repairs: unforeseen tasks necessary to repair damage, prevent failure or rapid degradation of equipment Reactive inspections: patrols or inspections used to check for public safety risks or conditions not directly related to the fault in the event of failure. We intend to implement the following corrective maintenance strategies for the ACS Other fleet. Instrument transformer repair policy Avoid invasive repairs of freestanding instrument transformers. It is generally more cost effective and lower risk to replace an instrument transformer than to undertake invasive repairs or reconditioning. Modern instrument transformers are hermetically sealed, with large amounts of solid insulation and minimal quantities of oil, and consequently they are largely maintenance free. Hermetically sealed instrument transformers can be difficult to properly refill after invasive maintenance. Reliability after invasive maintenance is poor, and costs of repair can represent a significant proportion of the replacement cost. Repairs will be limited to external items such as minor damage to porcelain, or deterioration of terminal boxes or main terminal palms and so on. 13 Where the number of potential repairs is deemed sufficiently high a Maintenance Project may be instigated to manage the repair work. Transpower New Zealand Limited All rights reserved. Page 54 of 60

58 Ageing bus posts ACS Other Primary Equipment Investigate concrete bus posts installed in the 1950s and 1960s and repair or replace them if necessary. There are 61 substations with ageing concrete bus support posts that should be investigated and refurbished or replaced to avoid failure. There are approximately 8,700 concrete posts at these sites. Six sites, including approximately 1,200 posts, have already been surveyed and remedial works completed. Based on these six sites, we estimate that approximately 5% of the existing posts will require repairs or replacement. A site-by-site programme of work is now planned, based on the experience of the six pilot sites, to determine the extent and magnitude of deterioration at each site and to prepare and implement a plan for repair or replacement of deteriorated posts Maintenance Projects As discussed in subsection 2.2.4, maintenance projects typically consist of relatively high value planned repairs or replacements of components of larger assets. Maintenance projects would not be expected to increase the original design life of the larger assets. Maintenance jobs are typically run as a project where there are operational and financial efficiencies from doing so. The drivers for maintenance projects include asset condition, mitigating safety and environmental risks, and to improve performance. Over the RCP2 period we do not currently intend to implement any maintenance projects on the ACS Other fleet. Disposal This section describes our strategies for the disposal of ACS Other assets. No divestment is planned for these assets Disposal Strategies The implementation of asset disposal has many similarities with capital projects, including consideration of cost, safety, environmental impacts and project management. Aspects that are specific to successful disposal projects include site restoration and termination of all support activities and planning. Disconnector and earth switch rationalisation Remove disconnectors and earth switches from substations where they are not required. Non-essential disconnectors include, but are not limited to: disconnectors between a transformer and associated circuit breaker bypass disconnectors (provided there are no constraints). The removal of redundant disconnectors and earth switches will be considered in the following situations: Transpower New Zealand Limited All rights reserved. Page 55 of 60

59 there is major work to be done on the bus maintenance costs are becoming excessive they could be refurbished and used as a spares. ACS Other Primary Equipment The purpose of disconnector/earth switch rationalisation is to remove non-essential equipment from our existing substations to reduce maintenance costs and complexity while still maintaining the flexibility required for system operation. During RCP2, we plan to remove six disconnectors from the Timaru Substation and five disconnectors from the Karapiro Substation. Capacitor voltage monitors Remove existing capacitor voltage monitors. Historically capacitor voltage monitors were fitted to CVTs with known generic faults or in poor condition. There are approximately 43 CVT monitors in service. The monitors were manufactured in the 1980s and 1990s, and being electronic devices are approaching end of life. In some cases, modern electronic protection schemes can be set to monitor the CVT voltage, making the CVT monitors unnecessary. Rod gaps Remove all existing rod gaps on power transformers. All modern power transformers are purchased with surge arresters, but they are only particularly critical for transformers with a medium risk or high risk of lightning strike and voltage surge. All older medium-risk and high-risk power transformers have had the rod gaps replaced with a more modern type of lightning surge protection. There are some rod gaps remaining on low-risk transformers, which will be removed because of their unreliability and risk of causing fault outages that would otherwise have been avoided. We plan to remove rod gaps from 26 power transformers. Safe and environmentally responsible oil disposal Ensure appropriate oil disposal practices are undertaken at substations. Substations use significant amounts of oil in some outdoor equipment, such as transformers and legacy circuit breakers. We use oil containment systems that collect oil spills and contaminated stormwater from transformer and circuit breaker bunded areas. Oil separators separate the oil and water, before discharging the treated water into the local drainage system, soak pit or other approved discharge point. The oil trapped by containment and separator systems is removed by specialist service providers using pumps, skimmers or oil-absorbing materials, and taken to an authorised reclaimer or refuse disposal site Divestment Implementation of divestment is primarily the change of ownership, but we must also remain aware of any safety and environmental issues and technical impacts on the Grid, such as a change in constraints and flexibility of Grid operation. Transpower New Zealand Limited All rights reserved. Page 56 of 60

60 The divestments of ACS Other equipment that will take place during the RCP2 period will be insignificant in the scheme of the total ACS Other strategy and therefore are disregarded in this fleet strategy. 4.6 Asset Management Capability We require national Grid assets and equipment to be managed, maintained, tested and operated to high standards of skill, professionalism and safety supported by high-quality asset knowledge and risk management tools. This will ensure satisfactory and safe functioning of the network while minimising whole-of-life costs. To achieve the required quality standards so as to prevent injury to workers, protect the public and their property from harm and prevent damage to our assets, the work is to be carried out only by individuals with competencies that are both appropriate and current. The capability strategies are described under three headings: Risk Management Asset Knowledge Training and Competence Risk Management Our approach to risk management is central to our asset management decision making as we weigh up the various costs and benefits of options such as replacement timing. We are developing asset health and criticality frameworks to improve and integrate our risk-based asset management. The strategy below discusses how we plan to progress this as regards the ACS Other fleet. Asset health models for ACS Other fleet assets Explore the potential for the development and application of asset health models for ACS Other fleet assets. We will explore the development of asset health models for several of the asset types covered by this strategy. These models will provide improved long-range forecasting and visibility of the high-level trends that are expected with given investment scenarios. Priorities for the development of further asset health models will include freestanding instrument transformers and freestanding disconnectors and earth switches Asset Knowledge Robust asset knowledge is a critical input into asset management decisions for assets covered by this strategy. While our knowledge of basic parameters, such as the instrument transformer age or make/model and external condition is currently adequate, some areas require improvement. Enhancement of asset knowledge for ACS Other fleet assets Review asset knowledge and condition assessment requirements for assets within the ACS Other fleet, and initiate required improvements. Transpower New Zealand Limited All rights reserved. Page 57 of 60

61 Improved asset identification and registration is required for disconnectors and earth switches to resolve inconsistencies in the identification of models and types. Improvements are also required in the collation, presentation and publication of engineering support information for disconnectors and earth switches. We will use sampling and detailed examination of populations of aged instrument transformers as outlined in subsection to provide improved asset knowledge to assist in managing the fleet. Improved condition scoring and reporting systems will be developed for the following classes of assets, to provide more consistent assessment: disconnectors and earth switches outdoor structures and buswork ODJBs local service equipment. The planned improvements include the use of photographic guides for ensuring consistency in assessments and the capture and storage of photographic records. A portion of our asset management database is currently decentralised. In particular, the test results, condition assessment reports and maintenance records of some assets covered by this strategy are stored electronically on an ad-hoc basis, and are not currently accessible from the core maintenance management system. We will define requirements for standardising and storing this information in a consistent manner in the core maintenance management system. We will also develop improved asset management decision making models for some of the assets covered by this strategy, particularly disconnectors and earth switches Training and Competence We require our assets and equipment to be maintained, tested and operated to high standards of skill, professionalism and safety to ensure satisfactory functioning of the network. We have three service specifications that define the competency requirements for employees and service providers working on primary equipment: TP.SS Minimum competencies for power system equipment operation TP.SS Minimum competencies for substations maintenance and testing TP.SS Minimum requirements for Transpower field work. We must maintain a minimum baseline of retained skilled workforce: engineers and site works operators who understand the physical assets. Setup and alignment of disconnectors Review and extend programme of training maintenance service providers in the correct alignment of disconnectors. Our competency requirements for service providers specify that substation maintainers must be competent in the operation, installation, maintenance and repair of disconnectors Transpower New Zealand Limited All rights reserved. Page 58 of 60

62 and earth switches (see TP.SS module SM.5). We have developed structured training programmes for service providers, including a training module on disconnectors and earth switches. Training is delivered at a facility where we have installed disconnectors of the main types found in service. The training focuses on the practical skills required to correctly assemble and align disconnectors. We intend to review of the overall effectiveness of the current approach. This review will aim to: raise the general level of awareness of the ongoing reliability issues caused by malalignment of disconnectors establish the extent of the training need (that is, how many service providers need to be competent in this area, and how many of these are demonstrably competent at present) increase the volume of training, to close identified gaps improve the delivery of the disconnector and earth switch training programmes provide practical and effective ongoing feedback and learning to service providers about disconnector alignment. Specialised maintenance service providers Continue use of specialist advisors for selected work. Our maintenance service providers do not generally have the skills required for some expert services relevant to the ACS Other fleet. In specific circumstances, we engage the services of specialist consultants and independent service providers to provide testing, analysis and recommendations for maintenance solutions. Specific examples where we may engage specialist services for work associated with this fleet include: assessment of deterioration of steel or concrete structures in substations, including the development of appropriate maintenance solutions modelling the performance of substation earth grids, and undertaking remote source injection tests to assess step and touch potential hazards. Transpower New Zealand Limited All rights reserved. Page 59 of 60

63 4.7 Summary of RCP2 fleet strategies ACS Other Primary Equipment Our strategies for the asset management of the fleet of ACS Other assets are summarised below for each lifecycle stage. Planning Enhancement and Development Complete the upgrade of the Islington low-voltage supply system, which commenced in RCP1. Identify and replace ageing and poor condition instrument transformers. Replace or refurbish disconnectors and earth switches when they reach replacement criteria. Replacement and Refurbishment Replace or refurbish busbar systems at 50 kv and above that present greater safety or performance risks than modern designs or impose operational constraints. Replace all gap-type surge arresters. Survey substation LVAC panels and undertake replacements based on condition criteria and install a main 400 V switchboard as required. Survey all ODJBs and replace units that meet replacement criteria. Upgrade the lightning protection system at substations where our standard is currently not being met. Cost Estimation Scope and estimate project works to a P50 confidence level; that is, the estimate is based on a 50% probability that the cost will not be exceeded. Delivery Design Procurement Where practicable and economic, standardise busbar systems as they become due for replacement. Standardise the LVAC system when the LVAC switchboard is replaced for increased reliability and flexibility. Procure disconnectors, earth switches and instrument transformers from the minimum possible number of vendors commensurate with the need to manage supplier risk. Operation Contingency Planning Maintain sufficient emergency spares in place to enable rapid restoration of transmission service following ACS Other equipment failures. Maintenance Carry out current injection tests, including voltage gradient tests on earth grids. Preventive Maintenance Corrective Maintenance Undertake pilot internal condition assessments of populations of older instrument transformers. Undertake systematic changes to maintenance of disconnectors to improve condition assessment processes and reduce instances of forced outages caused by mal-alignment. Avoid invasive repairs of freestanding instrument transformers. Investigate concrete bus posts installed in the 1950s and 1960s and repair or replace them if necessary. Disposal and Divestment Remove disconnectors and earth switches from substation where they are not required. Asset Disposals Remove existing capacitor voltage monitors. Remove all existing rod gaps on power transformers. Ensure appropriate oil disposal practices are undertaken at substations. Asset Management Capability Risk Management Asset Knowledge Training and Competence Explore the potential for the development and application of asset health models for ACS Other fleet assets. Review asset knowledge and condition assessment requirements for assets within the ACS Other fleet, and initiate required improvements. Review and extend programme of training maintenance service providers in the correct alignment of disconnectors. Continue use of specialist advisors for selected work. Transpower New Zealand Limited All rights reserved. Page 60 of 60

64 Appendices ACS Other Primary Equipment 31

65 A. ADDITIONAL SCOPE DETAIL The following assets are also included within the scope of other primary ACS substation equipment, but are not explicitly individually discussed within this fleet strategy because of their small contribution to expenditure and simple situations: SF 6 handling equipment test equipment cable tunnels air compressors cable trays insulators hardware and conductors. The types of primary equipment that are not covered in this fleet strategy because they have their own strategy document include: reactive power equipment (synchronous condensers, SVCs, STACOMs, capacitors, reactors, and resistors) transformers circuit breakers indoor switchgear HVDC equipment. Transpower New Zealand Limited All rights reserved. Appendices page 62

66 B. TYPICAL ALTERNATING CURRENT STATIONS OTHER ASSET PHOTOGRAPHS Figure 12 shows photos of disconnectors and earth switches in service. Figure 13 shows photos of instrument transformers in service. Figure 14 shows photos of outdoor junction boxes. Figure 15 shows photos of various Other ACS fleet assets. Centre rotating double break disconnector Vertical break disconnector Vertical earth switch Centre break disconnector Pantograph disconnector Figure 12: Photos of disconnectors and earth switches in service Transpower New Zealand Limited All rights reserved. Appendices page 63

67 Neutral current transformer (NCT) Current transformer (CT) Voltage transformer (VT) Figure 13: Photos of instrument transformers in service Figure 14: Photos of outdoor junction boxes Transpower New Zealand Limited All rights reserved. Appendices page 64

68 Neutral Earthing Resistor (NER) Oil containment tanks and plate separator Surge arresters Lightning protection masts Local service transformer Figure 15: Photos of various ACS Other fleet assets Local service switchboard Transpower New Zealand Limited All rights reserved. Appendices page 65