A practical approach to condition and risk based power transformer asset replacement

As with other utilities, National Grid is faced with a fleet of transformers, many heavily loaded, where the present age of many units is in excess of the expected design life. National Grid is pursuing a practical and iterative approach to replacement based on risk: a combination of condition and criticality. The process is iterative and makes best use of condition data and subject matter expert opinion, combined with consequence of unplanned unavailability. The result is a list of transformers targeted for strategic replacement and an `action plan' for all units based on tactical response which may include system reconfiguration.