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Analysing condition for better oil-filled plant management

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There is increasing pressure on all owners and operators of electrical systems to develop asset management strategies that are effective and cost efficient. Ensuring a corporately acceptable failure rate, prolonging the life of the assets, using appropriate maintenance strategies and planning for replacement are of paramount importance.

Over the past 15 years a wide range of projects have been completed within the Strategic Technology Program or STP at EA Technology The STP is sponsored by the Distribution Network Operators in the UK and is a means to research and expand our knowledge of HV plant. It was through this program that numerous projects relating to 11kV oil filled switchgear was completed. Consequently, the performance and degradation of oil filled switchgear has been studied in detail. This research work completed at EA Technology and supported by individual RCM studies, revealed that oil condition is the critical factor in determining the condition of the switchgear and the need for maintenance.

Consequently EA Technology offer a suite of services for oil filled assets, which includes:

Transformer Oil Analysis and Health Index

Transformer oil analysis is widely used and accepted method of assisting in determining transformer condition. We offer a wide range of oil analysis techniques. Perhaps the most pertinent analysis for transformers are:

  • Oil quality (moisture, acidity and electrical breakdown strength)
  • Dissolved Gas Analysis (DGA)
  • Furfuraldehyde content

In order to maximise the benefit of the oil analysis EA Technology offer a Health Index Service. This approach combines available relevant information on assets, including oil analysis results to derive a single number intended to give an indication of overall condition. From the health index we can estimate the probability of failure and proximity to end of life for transformers. In addition by applying an aging algorithm we can appreciate the future performance of the transformer and identify an appropriate maintenance and replacement strategy.


  • Maximises the use of available information, including oil analysis results, duty, environmental factors, fault history, age etc
  • Identifies transformers that would benefit from life extension measures or replacement
  • Accurate indicator of transformer condition identifying units at risk of failure
  • Enables informed asset management decisions to be made for transformer populations
  • The health index approach offers the initial steps to adopting a condition based risk management (CBRM) (change hyperlink) strategy

Ring Main Units and extensible switchgear

  • Live tank Oil Sampling (LTOS), a method of retrieving an oil sample causing minimum disruption to the system
  • Detailed laboratory analysis and report on oil and switchgear condition and the requirement for maintenance


  • Identify when assets do or DO NOT need invasive maintenance
  • Optimises maintenance schedules resulting in cost saving and improved safety and reliability of the network assets

Minimum Oil Circuit Breakers

  • Statistical sampling approach
  • Detailed laboratory analysis with detailed report, including findings and recommendations


  • Identifies appropriate asset condition and optimises maintenance intervals

For more details please contact: 0800 028 7243 or email sales@eatechnology.com

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