Partial discharge measurement and monitoring on rotating machines

With respect to the basic gas discharge physics, the rise time of an electron avalanche under nitrogen atmosphere results in a partial discharge signal bandwidth of several hundreds of MHz. However, in terms of high frequency properties, a rotating machine acts as a highly complex network. Mismatch of impedance and other effects hamper the applicability of different frequency bands for partial discharge testing. The epoxy-mica insulation system widely tolerates partial discharge. Thus, partial discharge activity often serves as an indicator for other defect mechanism, such as mechanical, thermal, or environmental influence.