A novel method for noise rejection during PD measurements in combination with pulse-width-modulation amplifiers

This paper describes a new method to avoid the noise influence on partial discharge (PD) measurements upon using pulse-width modulation (PWM) amplifiers. This is achieved by a special PD test set-up, where the test object, a coil with high inductivity, and a capacitance are put together to form a series resonance circuit. Energy is only applied to the measurement circuit by the PWM amplifier during a short period of time (e.g., between 0 and 90° phase angle). To avoid the noise generated by the PWM amplifier, the PD measurement is only carried out during its switch-off period. With this measurement set-up, it was possible to measure the PD behavior of the test object under high voltage as well as under high current conditions. By this, a new method was found to conduct PD measurements of coils with high inductivity and high capacitance under operation conditions