UHF monitoring of partial discharge in substation equipment using a novel multi-sensor cable loop

This paper describes the development of a partial discharge measurement system that utilises a multiplexed approach to ultra-high-frequency monitoring on many pieces of equipment using a single cable loop connected to only two sampling channels. It is envisioned that the system could be used in partial discharge monitoring of medium voltage metal-enclosed switchgear, or several power transformers within a distribution substation. Conventionally, ultra-high-frequency monitoring of high voltage systems has used an array of sensors installed on each unit to facilitate PD location within the unit. The proposed system allows multiple small units to be monitored simultaneously, thus potentially spreading the cost of the measurement hardware across many pieces of equipment. This capability comes at the expense of limiting the partial discharge location capability to a particular item of plant rather than to a specific location within it.