Practical experiences of on-line partial discharge measurements on a variety of medium-voltage electrical equipment

In recent years, there has been a considerable amount of discussion concerning partial discharge (PD) measurements on medium-voltage motors and generators. If one considers the total plant electrical distribution system and production equipment, motors comprise only a small part of the plant electrical equipment. If a motor should fail, part of production will likely be shut down and there will be lost revenue. However, there is a wide variety of other equipment in a facility, besides a motor, that can fail and can have a much more devastating effect on the plant's production. Additional items to consider for PD monitoring are the plant incoming transformers (they may be owned by the plant if the plant is purchasing primary power), the incoming switchgear, cables, bus duct, other remote substation switchgear, and power center transformers. Methods have been developed to monitor PD in all types of medium-voltage equipment. This paper discusses application of sensors, methods of measurement and data interpretation and present several case studies.