Condition monitoring of power transformer on-load tap-changers. II. Detection of ageing from vibration signatures

The paper describes a technique for online automatic condition assessment of an on-load tap-changer (OLTC) using a self-organising map (SOM). With a condition indicator giving the correct indication of the current condition status, an estimate can be made of the remaining life of the equipment. The condition assessment technique is demonstrated using the signatures collected by online monitoring systems installed on selector type OLTCs in distribution substations. Using the realtime fault detection procedure, reliable identification of incipient faults in the equipment can be achieved for the pre-specified false alarming rate