NETWORK CONTROL ANCILLARY SERVICE QUANTITY PROCEDURE

Transcription

1 NETWORK CONTROL ANCILLARY SERVICE QUANTITY PROCEDURE PREPARED BY: Electricity System Operations Planning and Performance DOCUMENT NO: 1.0 VERSION NO: 1.0 FINAL (Updated in July 2009 to reflect NEMMCO s transition to AEMO) Austrolicin Enorgy Morkot Oporotor Ltd AllN 9d on www oomo,t om.ou lnfo@o mo com au NF.W.;QlJTli WAIE., QlJrENSLAND OUTH /\U.,T~AllA VI TORIA AUST~AllAN CAPITAL TERRITORY TASMANIA

2 REVISION HISTORY VERSION DATE AUTHOR COMMENTS /02/2008 Dalibor Balicevic 01/07/2009 Dalibor Balicevic Initial version following Rules consultation. NEMMCO changed to AEMO Issue Date: 25 Feb 2008 Document No: 1.0 I

3 DISCLAIMER This document is made available to you on the following basis: (a) (b) (c) (d) (e) Purpose - This document is provided to you for information purposes only. You are not permitted to commercialise it or any information contained in it. Reliance - This document may be subsequently amended. Any reliance on this document is at your own risk. Intellectual Property AEMO Limited is the owner of the copyright in this document. All rights are reserved. All material is subject to copyright under the Copyright Act 1968 (Commonwealth) and permission to copy it, or any parts of it, must be obtained in writing from AEMO. AEMO is the owner of all other intellectual property rights in this document and the information contained in it. You must not in any way, or by any means, store, reproduce or modify it without AEMO's express written consent. No Warranty - Neither AEMO, nor any of AEMO s advisers, consultants or other contributors to this document (or their respective associated companies, businesses, partners, directors, officers or employees) make any representation or warranty, express or implied, as to the currency, accuracy, reliability or completeness of this document, or the information contained in it. No Liability - To the maximum extent permitted by law, neither AEMO, nor any of its advisers, consultants or other contributors to this document (or their respective associated companies, businesses, partners, directors, officers or employees) shall have any liability (whether arising from negligence or otherwise) in respect of your use of the information (including any reliance on its currency, accuracy, reliability or completeness) contained in this document Australian Energy Market Operator Limited is the owner of the copyright in this document. All rights reserved. Issue Date: 25 Feb 2008 Document No: 1.0 II

4 TABLE OF CONTENTS 1. INTRODUCTION 4 2. PURPOSE 4 3. APPLICATION OF THESE NCAS QUANTITY PROCEDURE 4 4. DEFINITIONS AND INTERPRETATION 4 5. TYPE OF NCAS REQUIRED TO BE PROCURED 5 6. DETERMINING THE QUANTITY OF NLCAS Objective Process Identify Transmission Power Lines at risk Collect required data Determine the NLCAS required to maintain power system security Determine NLCAS required to enhance network transfer capability 6 7. DETERMINING THE QUANTITY OF REACTIVE POWER ANCILLARY SERVICE Objective Assumptions Generation/Interconnector Transfer Assumptions Load flow assumptions Process Collect required data Develop a load flow base case Conduct simulation to determine reactive power reserve requirement Apply reactive power reserve safety margin Determine RPAS required to enhance network transfer capability 10 SCHEDULE 1: GLOSSARY 11 Issue Date: 25 Feb 2008 Document No: 1.0 III

5 1. Introduction AEMO is required to develop and publish an NCAS Quantity Procedure in accordance with Rule (b), which states: AEMO must develop and publish a procedure for determining the quantities of each kind of network control ancillary service required for AEMO: a) to achieve the power system security and reliability standards; and b) where practicable to enhance network transfer capability whilst still maintaining a secure operating state when, in AEMO s reasonable opinion, the resultant expected increase in network control ancillary service costs will not exceed the resultant expected increase benefits of trade from the spot market. In doing so, Rule (d) requires AEMO to comply with the Rules consultation procedures when making or amending descriptions or procedures under Rule This document constitutes the NCAS Quantity Procedure and has been developed in accordance with Rules (b) and (d). This NCAS Quantity Procedure commenced on 25 February This NCAS Quantity Procedure may only be amended in accordance with Rules (c) and (d). If there is any inconsistency between this NCAS Quantity Procedure and the Rules, the Rules will prevail to the extent of that inconsistency. 2. Purpose This document details AEMO s procedure for determining the number, type and location of NCAS required to be procured whenever AEMO acquires NCAS. 3. Application of these NCAS Quantity Procedure This NCAS Quantity Procedure applies to AEMO. 4. Definitions and interpretation a) In this NCAS Quantity Procedure, a word or phrase in this style, has the meaning set out opposite that word or phrase in the Glossary (Schedule 1). b) If a word or phrase in this style is not defined in the Glossary, the term has the same meaning as given to that term in the Rules. A reference to a Rule followed by a number is a reference to a provision in the Rules. Issue Date: 25 Feb 2008 Document No: 1.0 PAGE 4

6 c) Unless the context otherwise requires, this NCAS Quantity Procedure shall be interpreted in accordance with Schedule 2 of the National Electricity Law. d) The singular includes the plural and vice versa. 5. Type of NCAS required to be procured In accordance with the NCAS Description, there are two types of NCAS: network loading control ancillary service (NLCAS); and reactive power ancillary service (RPAS). 6. Determining the Quantity of NLCAS 6.1 Objective AEMO s objective is to determine the total NLCAS required to maintain the active power flows on Transmission Power Lines within their current ratings in accordance with the requirements of Rule (b). 6.2 Process These are the steps to be undertaken by AEMO in determining the quantity of NLCAS required: Identify Transmission Power Lines at risk AEMO will identify Transmission Power Lines at risk of being overloaded due to a single credible contingency event on a transmission network and consequently constraining interconnector flow Collect required data AEMO will obtain the following information: Interconnector active power transfer limits, continuous and short-term current ratings of Transmission Power Lines from the relevant TNSP; and A list of future committed transmission network and generation developments from the most recent relevant Annual Planning Reports, statement of opportunities and medium term PASA Determine the NLCAS required to maintain power system security If one of the Transmission Power Lines trips, the amount of NLCAS required is the largest amount of total loading of the remaining Transmission Power Lines above their continuous ratings, considering each Transmission Power Line in turn. The amount of NLCAS required is limited by the difference between the continuous and short-term current rating of the Transmission Power Lines, but might also be further reduced if the pre-contingent flow is Issue Date: 25 Feb 2008 Document No: 1.0 PAGE 5

7 limited below the level required to ensure the short-term rating will not be exceeded for other reasons, for example, voltage or transient stability. For Transmission Power Lines that are identical and in parallel, the amount of NLCAS required is calculated using the following formula, assuming the pre-contingent flow is determined by the short-term current ratings of the Transmission Power Lines: NLC = V * 3 * [MIN (OL, STR * (n - 1)) - CR * (n - 1)] where: NLC is amount of NLCAS required V is the post-contingent voltage of the Transmission Power Lines; MIN (OL, STR * (n - 1)) - CR * (n - 1)) represents the minimum of OL and (STR * (n - 1)) - CR * (n - 1)); OL is the pre-contingent operational limit for the set of parallel Transmission Power Lines expressed in Amperes; STR is the short-term current rating of each Transmission Power Line (consistent with the response time of the NLCAS) expressed in Amperes; n is the number of parallel Transmission Power Lines (pre-contingent); and CR is the continuous current rating of each Transmission Power Line. If Transmission Power Lines are not identical, loss of each Transmission Power Line needs to be considered separately and the amount of required NLCAS is the largest of the amounts determined. Load flow simulation is needed in more complex cases. The NLCAS must be provided in the appropriate region to have the desired effect, for example, as a load reduction in the importing region. If a credible contingency event occurs resulting in load reduction, power system frequency will change. AEMO's dispatch of market ancillary services will take this into account so that the effectiveness of the NLCAS is not diminished Determine NLCAS required to enhance network transfer capability AEMO will review the operation of the inter-regional system normal constraint equations with the most binding instances during the previous financial year to ascertain the NLCAS required to enhance network transfer capability when the resultant expected increase in NLCAS costs will not exceed the resultant expected increase benefits of trade from the spot market. Issue Date: 25 Feb 2008 Document No: 1.0 PAGE 6

8 7. Determining the Quantity of Reactive Power Ancillary Service 7.1 Objective AEMO s objective is to determine the total RPAS required, with an appropriate reactive power safety margin, to maintain the transmission network within voltage and stability limits in accordance with the requirements of Rule (b). AEMO will consult with relevant TNSPs in meeting the above objective. 7.2 Assumptions These are the assumptions made when determining the required RPAS: Generation/Interconnector Transfer Assumptions In the load flow base case all scheduled generating units required to meet 10% POE demand are assumed to be available and online. Committed new generating units, as reported in the most recent publication of statement of opportunities and medium term PASA, are assumed to be in service and are included in the power system model. If the total generation comprised of the existing scheduled generating units and future committed generating units is insufficient to meet 10% POE demand AEMO will model proposed generation projects as reported in the most recent statement of opportunities. When simulating credible contingency events the critical generating unit is taken out of service as a prior outage to allow variations in total generation availability to be examined providing that the generation available meets 10% POE demand. Generating units capacities are obtained from the most recent statement of opportunities. Interconnector transfer capability is assumed to be the transfer capability observed in the actual power system snapshot representative of peak demand day. If it is necessary to increase the transfer capability above that observed in the snapshot, this increase will not exceed the maximum interconnector transfer limit Load flow assumptions A power system snapshot representing high demand conditions will be scaled up to 10% POE forecast demand conditions to determine the reactive power generation/absorption requirements during peak demand conditions. A power system snapshot representing low demand conditions will be used to determine reactive power generation/absorption requirements during low demand conditions; Generation distribution patterns will be derived from actual power system conditions; Issue Date: 25 Feb 2008 Document No: 1.0 PAGE 7

9 Future committed transmission network augmentations, as detailed in relevant Annual Planning Reports are modelled and relevant TNSP control schemes would be taken into account as appropriate; All installed reactive plant is available and in service; The worst credible contingency event modelled is based on contingency analysis outcomes. Other contingencies may be checked by simulation; Prior transmission network outages are not considered because they would not be permitted to proceed if power system security could not be maintained; and AEMO will simulate an N -1 level of credible contingency events. 7.3 Process These are the steps to be undertaken by AEMO in determining the quantity of RPAS required: Collect required data AEMO will obtain the following information: Historical power system snapshots representative of high and low demand conditions, respectively; A list of committed transmission network developments and new generation proposals from the most recent relevant Annual Planning Reports, statement of opportunities and medium term PASA; and Generating unit reactive power capabilities from the performance standards. RPAS previously procured and dispatched by AEMO provides guidance to forecasting future reactive power reserve Develop a load flow base case The base case load flow will be developed from a power system snapshot representing the actual power system conditions. Future transmission network augmentations and new generating units that are committed projects will be included in the load flow model. The base case will then be used as a basis for studying various scenarios, such as high and low demand conditions, to determine maximum reactive power generation and absorption requirements. The span of studies will be dependent on transmission network augmentation and generation project information reported in the statement of opportunities and relevant Annual Planning Reports. Typically, three years of future committed transmission network augmentations and new generation projects will be considered. Issue Date: 25 Feb 2008 Document No: 1.0 PAGE 8

10 7.3.3 Conduct simulation to determine reactive power reserve requirement The requirements for reactive power are strongly locational. For example, RPAS from Queensland cannot assist voltage control in Victoria. Therefore, for this assessment, AEMO will divide the power system into areas of generation or load such that a requirement in an area needs to be satisfied from sources within that area due to the inefficiency of transporting reactive power. The areas of generation or load are determined based on critical locations within a transmission network, where a credible contingency event could result in a voltage collapse. AEMO will simulate critical credible contingency events at various locations and determine the amount of reactive power (if any) that is needed in each area in addition to supplies within each transmission network or otherwise available to them. The total reactive power requirement is that needed to maintain each transmission network within its voltage and stability limits. AEMO also considers past usage of reactive power as a guide to what will be needed in the future, and consults with the System Operators that control voltage on behalf of AEMO. The reactive power capability of a generating unit is the amount beyond the reactive power capability specified in the performance standards up to the limit specified in a capability diagram, similar to the example shown in Figure 1. Rated MW (Gen) = Pmax Active Power Output (MW) Rated Apparent Power Output (Rated MVA) = MBASE Stator Limit Under-excitation Limit [Area A] MVAr capability available to be contracted to NEMMCO [Area B] MVAr capability specified by performance standard [Area C] MVAr capability specified by performance standard [Area D] MVAr capability available to be contracted to NEMMCO Rotor Limit Reactive Output Power (MVAr) Reactive Power Absorption 0 Reactive Power Generation Level as set by the performance standard under Rules S Max tested Pmax Max tested Pmax Level as set by the performance standard under Rules S Issue Date: 25 Feb 2008 Document No: 1.0 PAGE 9

11 FIGURE 1. SAMPLE GENERATING UNIT CAPABILITY DIAGRAM AT NOMINAL VOLTAGE Apply reactive power reserve safety margin The total reactive power requirement is that needed to maintain the transmission network within its voltage and stability limits. On top of the amount of reactive power determined in accordance with Step 3, a reactive power safety margin is applied to determine the total RPAS requirement. The reactive power safety margin to be applied is the greater of: a) At least 1% of the maximum fault level at each connection point (expressed as capacitive reactive power in MVAr) as required by Rule S5.1.8; and b) The MVAr capacity of the largest capacitor bank relevant to a location Determine RPAS required to enhance network transfer capability AEMO will review the operation of the inter-regional and intra-regional system normal constraint equations with most binding instances during the previous financial year to ascertain the RPAS required to enhance network transfer capability when the resultant expected increase in RPAS costs will not exceed the resultant expected increase benefits of trade from the spot market. Issue Date: 25 Feb 2008 Document No: 1.0 PAGE 10

12 Schedule 1: Glossary In this document, the listed words and phrases have the following meanings: DEFINED TERM MEANING AEMO has the meaning given to it in the Rules, previously known as the National Electricity Market Management Company (NEMMCO) AVR Automatic Voltage Regulator, regulates generating unit terminal voltage by varying its reactive power output. Committed In the context of a transmission network development or a generation project, it refers to those projects that are described as such in the relevant Annual Planning Report, or statement of opportunities, as the case may be. NCAS Network control ancillary services, as defined in the NCAS Description NCAS Description The description referred to in Rule (a). NCAS Quantity Procedure This document. NLCAS Network loading control ancillary services, as defined in the NCAS Description. 10 % POE A 10% probability of exceedence of load forecast used by AEMO for the purposes of determination of short term capacity reserve and medium term capacity reserve requirements under the power system security and reliability standards referred to in Rule 4.9.1(e). Reactive power safety margin The amount of reactive power (in MVAr) to be added on top of the reactive power reserve requirement to obtain the total amount of RPAS RPAS Reactive power ancillary services, as defined in the NCAS Description. Rules National Electricity Rules Issue Date: 25 Feb 2008 Document No: 1.0 PAGE 11

13 Transmission Power Line A transmission line or group of transmission lines that: (i) connects the transmission networks in adjacent regions; or (ii) impact on the active power flow across adjacent regions. TNSP Transmission Network Service Provider Issue Date: 25 Feb 2008 Document No: 1.0 PAGE 12