Application of pulse width analysis to partial discharge detection

An online partial discharge test for large steam turbine generators has been developed whereby partial discharges and noise are distinguished on the basis of pulse width. The pulse signals are detected by stator slot couplers (SSCs) which are permanently installed within the generator. Experiments have shown that partial discharge pulses, as detected by an SSC, have a pulse duration of only a few nanoseconds, whereas all types of electrical noise have a pulse width of greater than 20 ns. An instrument called the TGA, which performs a pulse width analysis with a resolution of 2 ns, has been constructed. This instrument permits the rejection of noise on a pulse by a pulse basis and provides pulse height and pulse phase analysis of the partial discharge pulses. The SSC/TGA test allows nonspecialized personnel to perform a partial discharge test on generators in nuclear and fossil stations, without requiring a generator outage