Oil Diagnostics - Test Information

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1 Oil Diagnostics - Test Information For both financial and operational reasons it is very important that transformers are managed efficiently. Optimising the future management of large transformers on networks to maximise the utilisation and full potential life of existing transformers and to ensure appropriate remedial actions and replacement policies are undertaken to prevent significant numbers of failures, will have a major impact on the financial and operational performance of the owners. EA Technology offers a wide range of analytical specification tests coupled with expert interpretation and reporting systems. The following sections describe some of the key analytical tests carried out on transformer oil samples: Dissolved Gas Analysis (DGA) IEC The essential purpose of dissolved gas analysis is to detect gases generated due to thermal degradation of insulation components within the transformer. In particular the aim of gas analysis is to provide prior warning of a developing thermal fault i.e. local overheating, discharge activity or arcing and sparking within the transformer. It is normal practice to measure nine gases in an oil sample. Nitrogen, oxygen, carbon monoxide, carbon dioxide and the five hydrocarbon gases hydrogen, methane, ethane, ethylene and acetylene. The five hydrocarbon gases and carbon dioxide and carbon monoxide can be formed as a result of a thermal decomposition of oil. These therefore provide the opportunity for identifying the presence of faults or developing faults which give rise to heating in the transformer. The relative amounts of the different gases generated change with changing temperature, therefore providing the possibility of identifying different types of faults by the relative concentration of the different gases. For each of the gases the absolute value is considered and then the ratio of various gases is looked at in order to give information on the nature and severity of a potential fault. Oil Quality o Moisture IEC60814 o Acidity IEC o Breakdown Voltage Strength IEC 60247

2 This includes moisture, acidity, and electrical breakdown strength. These parameters are primarily intended to give information on the condition of the oil, although indirectly they also provide some information on the condition of the transformer. The moisture content is particularly relevant to transformer condition. Maintaining acceptable oil quality is critical in preventing premature aging of the transformer and therefore can assist in determining appropriate life enhancing measures. Furan Analysis (Paper Insulation Assessment) IEC Furan detection has become accepted as a means of monitoring the degradation of paper insulation in transformers. Paper consists of cellulose molecules which have very long carbon chains. As the paper ages the carbon chains are progressively broken into shorter lengths with the subsequent reduction in the mechanical properties of the paper. Bi-products of the chain breakdown are organic compounds known as the furanic (furans) family. This information is extremely useful in determining the condition of the paper insulation and therefore the transformer as a whole. Generally once the paper insulation has reached the end of its life the transformer can also be considered to be at the end of its life. This information can assist in making informed decisions regarding the replacement strategy for transformers. PCB Analysis IEC Polychlorinated biphenyl (PCB) content of the oil is purely an environmental issue. The presence (at any level) of PCB has no significance for the condition or performance of a transformer, PCB is a very effective insulating liquid and is entirely compatible with oil. Therefore the significance of the measured levels is determined by the local environmental regulations. Polychlorinated Biphenyls were widely used as a fire retardant and insulator in the manufacture of transformers and capacitors. This was due to their ability to withstand exceptionally high temperatures. Because of their classification as a human carcinogen, the Environmental Protection Agency (EPA) banned their use in It should be noted that PCB content in HV transformers is stable and only one test is required on the oil. Dissipation Factor (Power Factor) IEC The Dissipation Factor measures the leakage current through the oil, which can assist in understanding the presence of contamination or deterioration of the transformer within the oil.

3 Interfacial Tension (IFT) ASTM D971 The interfacial tension between oil and water provides a means of detecting soluble polar contaminants and products of degradation. This characteristic changes fairly rapidly during the initial stages of ageing but levels off when deterioration is still moderate. A rapid decrease of IFT may also be an indication of compatibility problems between the oil and some transformer materials (varnishes, gaskets), or of an accidental contamination when filling with oil. However, oils with interfacial tension values at or near the lower limit value may or may not need to be investigated further and is highly dependent on the Oil Quality results. With overloaded transformers, the deterioration of materials is rapid and IFT is a tool for detection of deterioration. Viscosity IEC Oil viscosity is an important controlling factor in the dissipation of heat. Ageing and oxidation of the oil tend to increase viscosity. Viscosity is also affected by temperature, such that in a cold climate it is important that the viscosity is sufficiently low to enable adequate oil circulation. Density (Specific Gravity) ASTM D1524 The Density (Specific Gravity) of the oil is the ratio of the weights of equal volumes of oil and water. A high density indicates the oil's ability to suspend water and in extremely cold climates this can be used to determine whether ice will float on the oil potentially resulting in flashovers. Colour & Appearance ASTM D1500 The Colour and Appearance of the oil indicates the level of contamination caused by deterioration of the oil or insulating materials. The colour of the oil is compared to a specified spectrum of colours. Inhibitor Content (DBPC) IEC Inhibitors are added to the oil to replace the natural oxidation inhibitors. The inhibitors increase the resistance to the oxidation of the oil and assist in preventing degradation. As the oil is exposed to oxidation the oil is protected by the inhibitors and they are used up in the process. Once the inhibitors are depleted the oxidation and degradation of the oil will occur at a faster rate. Monitoring the inhibitor content allows this degradation to be prevented by topping up the inhibitor as required before it reaches depletion.

4 Corrosive Sulphur Assessment IEC Copper in direct contact with the oil and at a high temperature, can cause a corrosive reaction. From this the by-product copper sulphide will be formed, which will float in the oil and deposit between the windings. Copper Sulphide will reduce the electric strength of the insulation causing inter-turn faults. Dibenzyl Disulfide (DBDS) Dibenzyle Disulfide (DBDS) is one of several sulphur compounds known to cause copper corrosion in transformers under certain circumstances. Remedial processes such as absorbents, absorbents and oil change-out have been known to reduce the concentration of DBDS in the oil. However, if not destroyed or removed below several mg/kg (ppm), breakdown of the DBDS can still cause corrosion of the copper and the formation of copper sulphide. Passivator Content Passivator in Oil whether in the oil originally or after it has been added, this test provides information on the amount of passivator present in the oil by detection of Irgamet 39 along with similar type products. This test does not determine if there is corrosive sulphur. Passivators are used to retard the formation of copper sulphide. Additional testing is also available EA Technology can also offer an additional range of more bespoke testing such as Filtration, Particle assessment, Flash Point and Pour Point to build up a testing programme to meet the specific requirements of individual clients Oil Diagnostics Suite Package Information The standard diagnostic testing is offered in specific diagnostic suites designed to provide the maximum condition information on the transformers. The standard test suites are designed for individual samples to deliver a routine set of oil analysis at low cost. Standard Suite Packages: EA Technology s standard packages offer a range of tests reported in a single page report with traffic light status identification or detailed in an excel based report. All reports detail the transformer information, test results, recommendations and retest intervals. Below are examples of standard packages available, however EA Technology can match any analysis required to meet the client s requirements. Test suite TS2 is considered to be the best

5 option for Transformers as it provides the optimum information on the assets and allows for an overall assessment of its condition. Standard Suite TS1: Basic Routine Analysis designed for low cost assessment DGA and Oil Quality Standard Suite TS2: Routine Analysis designed for low cost assessment DGA, Oil Quality and FFA Analysis Standard Suite - TS3: Routine Analysis designed to cover Health & Safety requirements DGA, Oil Quality, FFA Analysis & PCB Standard Suite TS4: Full Analysis designed to give a complete assessment of the oil DGA, Oil Quality, FFA Analysis, PCB, IFT, Dissipation Factor Standard Suite TS5: Full Analysis designed to give a complete assessment of the oil Cold Climate DGA, Oil Quality, FFA Analysis, PCB, IFT, Dissipation Factor, Viscosity and Density Oil Diagnostics Reporting There are a number of reporting options that could be considered form individual PDF reports through to excel spreadsheet report options. EA Technology s standard package suites offer a range of tests which can be reported in a single page report with traffic light status identification. All reports detail the transformer information, test results, recommendations and retest intervals.

6 EA Technology recommend utilising an excel based report which details all the sample information, results, interpretation, testing standards and upper and lower threshold limits. All results showing issues are colour coded for ease of viewing and assessment and the indepth DGA interpretation such as Rogers Ratio & Duvals Triangle data can be provided on the report as required.

7 Oil Diagnostics Health Index (Advanced Assessment) The Health Index Suites are designed to give optimum condition information coupled with our expert asset management knowledge offering a cost effective asset management solution for an individual transformer or full site housing entire networks. Our Health Index reports detail all aspects of the analysis results, interpretation, discussion and recommendations for asset management strategies. The current and future condition of each transformer is detailed with an assessment of the end of life. The reports also include all the individual standard one page reports as detailed above. Health Index Suite - THI1: Health Index Assessment, DGA, Oil Quality and FFA Health index Suite THI2: Health Index Assessment, DGA, Oil Quality, FFA and PCB Oil Diagnostics Data Management Data management and handling is a vital part of any project. In Oil Diagnostics we operate an in-house purpose built Sample Processing Database. All samples are logged into the database and given a unique ID. The system allows the units to be booked in, result logging, project monitoring and secure approval. The system also automatically generates and sends notifications to clients (batch bases, not individual sample basis).

8 This system minimizes any internal data management issues and allows us to accurately manage the samples through the facility. Consideration could be given to providing the full list of transformers and their details upfront so they can be pre-uploaded into a data handling database. They can then be matched and the samples can be logged against the records accurately, minimizing data errors. Any miss-matches or issues with the samples would be reported for clarifications on sample identification. Oil Diagnostics Transformer Oil Sampling Sampling the transformers correctly is vital to ensuring an accurate oil result. The result is only as good as the sample provided. There are a number of sampling methods used in the industry; it is recommended that the sampling procedure used is in accordance with the IEC EA Technology have a number of highly trained Technical Engineers who visit client sites and take the oil samples from oil filled assets. Whilst on site our Engineers carry out an onsite risk assessment to ensure all risk factors have been taken into account before sampling takes place. All samples are taken using 500ml glass bottles with polycone caps to prevent gas escape. No sampling is permitted in plastic vessels for transformers. All bottles are transported in

9 crates containing 12 bottles, with sturdy foam oil resistant inserts to ensure safe transportation of the samples. A specific sampling kit is used to ensure the sample is taken correctly and ensure an accurate and clean sample is drawn off preventing contamination. The system uses a bung system in the sample tap leading to the bottle cap which has an inlet flow and outlet air vent to allow the oil to fill from the bottle of the bottle at a steady rate to minimize turbulence in the oil. The flowing temperature of the oil should be taken and recorded on the label to allow an accurate assessment of the moisture content.

10 Oil Diagnostics Crates & Logistics EA Technology utilise blue transportation crates containing 12 bottles, with sturdy foam oil resistant inserts to ensure safe transportation of the samples. All crates come pre-labelled with return address and contact information of EA Technology s Oil Diagnostic Facility. Inside they contain the foam insert system, 12 amber / clear glass bottles, sample labels and elastic bands, along with laminated sampling guide and fill level and cable ties to secure the lid before return transportation. Individual sampling tubes containing 1 bottle and label can be provided for one off samplings. All crates should be returned full of bottles to ensure safe transportation, empty bottles should be returned with the samples if a full crate of samples is not required.

11 No other packaging is required and the crates are ready to ship / transport either by a designated courier, drop off directly at EA Technology s Oil Diagnostic Facility or collected by EA Technology by contacting the lab on the lab Hotline number detailed on every crate and sample label. Simply take the samples from the oil filled assets, fill in a sample label with asset information and attach to the bottle, place the bottle in the crate, close the lid and secure with the cable ties provide and then arrange delivery / collection as required. Crates are dispatched on award of contract and can be stored on site ready for sampling to commence, this usually takes around 24hours to allow for crates to be delivered to site. Crates can be sent in advance and kept on site or stored in Engineers vans for ease of sampling and return.

12 Oil Diagnostic Facility EA Technology Europe Unit 4 Capenhurst Technology Park Capenhurst Chester, UK CH1 6ES Lab Hotline: OilData@eatechnology.com Jonathan Lewin Oil Diagnostics - Proposition Lead Direct Tel: Jonathan.Lewin@eatechnology.com