A modern approach to differential partial discharge diagnosis

Published in 2015

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Summary

In this paper, a novel approach for differential electrical partial discharge measurement is presented. A computer-controlled measurement bridge is combined with a digital partial discharge measuring system. Partial discharge signals decoupled with two conventional measuring impedances are balanced and subtracted within the measurement bridge. Since partial discharge events occur as differential-mode signals within the circuit whereas disturbances from the voltage source or from ground occur as common-mode signals, the differential interpretation of the signals may lead to an improvement of the signal-to-noise-ratio. Like conventional measuring bridges, the measurement setup may consist of two devices under test or a combination of a device under test and a coupling capacitor. The measurement bridge and the acquisition unit of the measurement system are battery-powered and controlled via fibre optics. Therefore, the measurement equipment itself shows low sensitivity to interference. Additionally, the setup can be placed on high voltage potential. Thus, using the introduced system, differential partial discharge measurement can also be performed on test objects on which decoupling in the ground path is not possible. Since the measurement bridge is computer-controlled, the measurement data is used for semi-automatic parametrization of the measuring bridge. The parameters of the bridge are calculated according to the frequency setting of the partial discharge filter. This method has proven to lead to a user-friendly and time-saving workflow. Using the described approach, efficient denoising of partial discharge measurements can also be achieved in asymmetrical setups.