REJECTION OF NARROW-BAND NOISE AND REPETITIVE PULSES IN ON-SITE PD MEASUREMENTS

This paper deals with the possibilities of noise suppression in partia l discharge (PD) measurements under on-site conditions. After the pres entation of previous work, a new concept of designing a digital FIR fi lter with a fixed order to suppress narrow-band disturbances will be p resented. The method will be compared to a design using adaptive filte rs. A filter device, which was developed as an extension for a convent ional PD detector, will be presented. In the second part of the paper, a method for suppressing pulse shaped noise synchronous to the test v oltage will be discussed. The disturbing pulses are detected automatic ally in a PD signal by comparing several recorded cycles of the test v oltage. There are two possibilities to suppress the pulses. The first one is an off-line method that allows attenuation degrees up to 30 dB, the second one works on line, and can process continuous PD signals. For the latter case a suppression of 14 dB for worst case pulses is po ssible with the developed hardware. In order to demonstrate the abilit ies of the filters, several measurements will be shown.