Detection and suppression of corona discharges during PD-measurement by means of RI-reception

In most cases sensitive on-site partial discharge (PD)-measurement on an apparatus is impossible in the presence of corona discharges at the high voltage conductors or near to the apparatus. A separation of internal PD and external corona discharges by pulse shape classification isn´t possible because of the bandlimiting measuring method of the conventional PD measuring instruments. The presented approach makes use of the radiated electromagnetic fields of corona discharges in the frequency range up to 100 MHz in order to get a specific pulse classification criteria. The reception of the electromagnetic (e.m.) fields by means of rod or loop antennas connected with a wide band measuring receiver provides a signal in addition to the bandlimited signal of the PD measuring circuit. By signal correlation it is possible to eliminate the corona pulses in the PD signal. Measurements in a laboratory set-up were performed. The results of the application of the new filter and correlation method are shown