Design of a Notch Filter to Improve the Specificity in Detection of Partial Discharge Sources

This paper describes the design of a notch filter that plays a vital role in ultra -high-frequency (UHF) sensor based online partial discharge (PD) monitoring systems. Most of the UHF sensors designed for the detection of PD signals have a wide bandwidth range from 0.3 GHz to 3GHz. Hence it is very difficult to avoid the false detection of PD due to strong interference by the mobile subscribers GSM frequency bands. In this work, we present the design of a notch filter operating at 0.9 GHz center frequency, to mitigate the problem of false detection of partial discharges by the GSM(2 Omega) band in India. The filter structure includes a step impedance stub along with the 50 Omega line on the signal plane. The proposed filter has au FBW of 53.3% and a size of (62mm x 24.5 min).