Period base maintenance is now being replaced by condition based maintenance.
The only moving parts of power transformers are in the On Load Tap Changer (OLTC).
As such parts are suffer from various aging mechanisms caused by mechanical malfunction, increased contact resistance, contact wear etc.
New technology seeks to extend the service interval and monitor OLTC condition to avert catastrophic failure, reduce maintenance cost and increase reliability.
Use of this diagnostic technique reduces required number of maintenance visits, cost, reduction in the number of catastrophic failures and interruptions to supply increasing the reliability of power delivery.