Partial discharge mapping of medium voltage cables-TNB´s experience

The ability to preactively diagnose the dielectric integrity of cables in service could greatly assist the utility in formulating a cost effective maintenance program and at the same time ensuring good quality supply to its customers. In line with this objective, Tenaga Nasional Berhad (TNB) has embarked on some intensive exercises to evaluate the effectiveness of those diagnostic techniques that are commercially available in the market. Partial discharge mapping is one of the techniques that had undergone extensive field trial in TNB. The paper discusses in detail the utility´s experience on this study which includes: (i) measuring the partial discharge activities in 209 medium voltage cables; (ii) conducting conjuncture tests of partial discharge mapping and very low frequency testing on 27 feeder circuits that were prone to frequent failure; and (ii) examining the correlation between the magnitude of partial discharge activities and probability of time to failures