Advantage of On-Line Partial Discharge continuous monitoring of medium voltage substation

On-line continuous partial discharge measurements of medium voltage substations have not attracted the same attention in the electrical community as compared to similar PD measurements of rotating machines. The cost of an unexpected outage however may be considerably more significant of a main distribution bus than just for a single motor failure. This paper discusses pros and cons of PD measurements using multiple sensors for additional noise reduction and localizing PD activity for measurements made in higher frequency bands. The importance of continuous PD monitoring vs. periodic walk in PD measurements of switchgear is also discussed considering that PD activity in switchgear can have very unstable activity highly dependent on ambient conditions. Negative periodic PD tests in switchgear can result in a false sense of security. Case studies from field experience are presented to support the discussions.