Evaluation of digital filters for rejecting discrete spectral interference in on-site PD measurements

Abstract

A B S T R A C TWhile Partial Discharge (PD) measurements are widely used in testing power apparatus after manufacture, there is now a trend to extend them to on-site measurements. The major problem encountered in the latter measurements is the strong coupling of external noises particularly from discrete spectral interferences (DSI) e.g. broadcasting stations as well as impulsive disturbances. A critical study of the performance of several digital filters for rejecting DSI is reported. The filters are evaluated with particular reference to distortion introduced on successive PD pulses. A new digital filtering method based on a cascaded 2nd order IIR lattice notch filter has been proposed. The study showed that, for similar performance, methods based on linear prediction required longer filter orders when compared to cascaded IIR notch filters. The nonadaptive methods were found to be stable against impulsive disturbances while adaptive methods were unstable. The new method proposed in this paper gave the best performance, low distortion to a sequence of PD pulses, good stability and fast filtering time. The performance at higher sampling rates, even with PD pulses of long widths was also found to be superior. Further, the method is implementable using fixed-point arithmetic leading to faster processing. Hence, the proposed method can be suggested for on-site PD measurements.

A Review of Online Partial Discharge Measurement of Large Generators

“…Based on the power spectrum density (PSD) of detected signals obtained by FFT, in conjunction with threshold optimized by fuzzy C-mean (FCM) adaptively, Luo et al [72] proposed an extractive method by searching DSI frequencies in PSD and compensating these frequencies smoothly with a compression ratio, which outperforms the wavelet-based denoising methods. As regard to filtering, there are several filters have been employed to suppress the PD signals, such as infinite impulse response (IIR) filter, finite impulse response filter, notch filter [73] and adaptive filter [74]. In [73], Nagesh et al evaluated various types of digital filters based on pulse distortion and filtering time, and found the cascaded 2nd order IIR lattice notch filter outperformed the others in DSI removal.…”

“…As regard to filtering, there are several filters have been employed to suppress the PD signals, such as infinite impulse response (IIR) filter, finite impulse response filter, notch filter [73] and adaptive filter [74]. In [73], Nagesh et al evaluated various types of digital filters based on pulse distortion and filtering time, and found the cascaded 2nd order IIR lattice notch filter outperformed the others in DSI removal. However, the filterers face difficulty in determining the frequency of disturbance and demerit of time-consuming, and may cause pulse attenuation and thus waveform distortion, which hampers subsequent PD pattern recognition.…”

Application of signal‐adapted wavelet to on‐line partial discharge measurement

“…It is becoming popular for the de-noising of PD signals and shows strong power [1][2][3][4]. However, it is found that the effectiveness of de-noising depends on the mother wavelet chosen.…”

Features Extraction and Mechanism Analysis of Partial Discharge Development under Protrusion Defect

“…However, the existing research of PD online monitoring focus on signal de-noising [3][4][5][6], PD sources location [7] and pattern recognition [8][9][10][11], PD severity assessment was rarely involved. To evaluate PD severity, the insulation dielectric property of GIS is the basic characteristic of the PD development process.…”