Comparison of HV on-line condition monitoring

In-service condition monitoring of HV electrical plant (generators and HV motors) has expanded greatly in recent years. A number of different systems have been developed, some more successful than others. The relative effectiveness of the different monitoring systems is therefore of great importance in selecting the best method for installation for the type of plant to be monitored. This paper briefly reviews why in-service condition monitoring is needed and why it is cost effective. It reviews three of the available in-service monitoring systems and compares their relative sensitivities for the detection of partial discharge (PD) under simplified laboratory conditions. It considers the need for sensitivity checking or normalisation in result interpretation and comments upon the value of offline monitoring tests in support of in-service machine condition monitoring.