A distributed PD detection method for high voltage cables based on high precision clock synchronization

• This paper presents a method that effectively solves the problem of uncabled multi-node synchronization in cable distributed PD detection. A distributed PD detection system configuration consisting of two terminal ends and several joint ends is also proposed. It significantly improves the test efficiency of field tests . Cables can be effectively tested even if they are buried directly in the earth or installed in pipes. • To ensure that each node can effectively receive the CS signal , the LFM signal is selected as the CS signal , which will be compressed to a narrow pulse after matched filtering. The process of matched filtering produces a gain of 43dB, which makes the identification of the arrival time of the CS signal independent of noise and the PD signal. • A signal separation algorithm based on STFT is proposed to eliminate the influence of the CS signal on PD signal recognition. It’s mainly based on the narrow-band characteristics of the LFM signal in a short timepiece. The slight distortion in the PD signal after reconstruction can be tolerated, and the effect on PD detection can be ignored. Partial discharge (PD) is a crucial cause of high voltage (HV) cable failures. Detecting and locating PD efficiently and effectively is paramount for HV cable maintenance. However, the attenuation of the PD signal after long-distance propagation makes it challenging to identify. This paper presents a distributed PD detection method that significantly reduces the propagation distance of PD signals before the sensor captures them. The technique uses the time-of-arrival to locate PD, whose localization accuracy is directly linked to the clock synchronization (CS) accuracy. CS between different sensors is achieved through three times interactions of the CS signal. The linear frequency modulation (LFM) signal is selected as the CS signal, which can generate a significant gain after pulse compression. It ensures that the CS signal can be effectively recognized after the attenuation of long-distance propagation. The paper also introduces a signal discrimination method based on the short-time Fourier transform that eliminates the influence of the LFM signal on PD identification. The cableless CS method makes it easier to set up before the onsite test. A prototype was implemented and tested. The CS accuracy was measured within 4 ns in the laboratory. An onsite test was carried out to evaluate the performance of the distributed PD detection system. A defect was found at a joint location, which was also confirmed by an additional ultrasonic PD test.