An Advanced Filtering Method for Partial Discharge Measurement in the Presence of High dV/dt

Abstract:
This paper introduces an advanced filter method enabling partial discharge (PD) detection at low apparent charge values during high dV/dt switching. Rising dV/dt results in higher switching noise frequencies. For sufficient damping of the switching noise, the cutoff frequency of the commonly used frequency filters in PD measurement systems has to rise too. This also weakens the desired PD signal resulting in a lower sensitivity. By filtering the sensor signal in the time domain, the signal-to-noise ratio can be improved. This method uses a noise mask which is generated from the switching signals to suppress switching noise. The filter is examined in a H-bridge test setup stressing the insulation of a single tooth motor winding.