Transformer Asset Life Extension – When, Why and How to Apply Continuous Condition Monitoring Systems

When managing an aging and/or failing HV power transformer fleet, an Asset Manager when faced with an unexpected imminent `end of life' defined test result, has two predominant decision paths available - to either define and justify an intervention of the asset - which may be aged but in good enough condition to satisfy its requirements, whilst still ensuring the required level of reliability at a limited cost; or to implement mitigation solutions that will keep the unit in service until a planned replacement can be facilitated. Once an outage and expenditure for either a maintenance repair or life extension intervention has been justified, planned and performed, the asset needs to be protected, risks managed and monitored closely, to ensure that the detected fault or accelerated aging marker has been eliminated or halted. For this, there are many online condition monitoring options available.Through this paper we will explore and detail the methods of approach and items to be considered recommended by the IEEE and CIGRE expert communities for Power Transformer Life Extension and Condition Monitoring. We will touch on the methods used globally by substation asset owners to justify asset repair and refurbishment versus life extension or replacement, recommended versus non-recommended interventions, and condition monitoring options used to keep a close eye on important assets.