Abstract: Monitoring apparatus for monitoring partial discharge activity in an AC electrical system comprises: a pair (60) of high- and low-frequency sensors; a timing module arranged to receive a cyclic signal from the low-frequency sensor and to provide a timing signal derived from the timing of successive cycles of the cyclic signal; and a monitoring unit (66) arranged to digitise a signal from the high-frequency sensor, to capture the digitised signal as consecutive data blocks of varying duration, and to trigger the capture of each data block in response to the timing signal. A condition monitored electrical system comprises a variable-speed drive (VSD) and a motor (M) operated by the drive, wherein the pair (60) of sensors is arranged at an end of a cable supplying power from the drive to a winding of the motor.

Abstract: Apparatus for remote monitoring of partial discharge events in electrical apparatus 1 includes one or more sensors 5 for detecting partial discharge pulses in one or more conductors 2 conveying electrical power to the apparatus. A programmed computer 5 analyzes measured pulses and discriminates between those originating from the apparatus being monitored and elsewhere. Discrimination is achieved by analyzing pulse shape, and by comparing pulses to partial discharge events measured locally to the sensors. The apparatus enables partial discharge events in electrical apparatus to be monitored without having to install sensors at the equipment itself.

Abstract: Apparatus for remote monitoring of partial discharge events in electrical apparatus 1 includes one or more sensors 5 for detecting partial discharge pulses in one or more conductors 2 conveying electrical power to the apparatus. A programmed computer 5 analyses measured pulses and discriminates between those originating from the apparatus being monitored and elsewhere. Discrimination is achieved by analysing pulse shape, and by comparing pulses to partial discharge events measured locally to the sensors. The apparatus enables partial discharge events in electrical apparatus to be monitored without having to install sensors at the equipment itself.