Online detecting PD of the stator insulation of generators is a good way to find some primary defects. But there are many kinds of pulse noises must be eliminated. Different places and sensors are used to get PD signal and remove noises at the best. In this paper, a new partial discharge detecting system for stator insulation of generators is put forward. It consists of three unconnected sensors, a filter, a data acquired system and a computer. The sensors are placed near but not connect with the three high voltage buses of the generator respectively. PD signal is measured by the sensors and processed by computer, including pulse noises elimination. According to the polarity of the signals from the electric coupler and magnetic coupler in one sensor, noises coming from other devices of power system can be banished. Other kind of noises, such as pulses from exciter, rotator brush, earth and space, are found have certain characteristics at the outputs of the three sensors. These characteristics are used to eliminate the noises. Experiments on a small generator and a sect of insolated phase bus ware carried out to demonstrate above theory.
