Experimental study of partial discharge pulses propagation in stator winding of hydro generator

The propagation of PD pulses through the winding, from the discharge site to the sensor location, is influenced by the frequency of signal and the geometry of generator, which is of critical importance for accurate measurement of the PD signals. The previous researches on PD propagation were mainly made on turbine generator or motor, little work had been done on hydro generator. To address this concern, an experimental study of the propagation of PD pulses in the stator winding of a large hydro generator is presented in this paper. In the test, the insulation outside slot exit of 22 bars was removed to directly inject PD pulses to the inner conductor. The results indicated PD signals manifest two modes when propagating in stator winding of large hydro generator, and 5MHz is the corner frequency of them. The coupling between bars in slot or overhang will cause crosstalk between phases, which obscures PD source location.