Time Difference Algorithm Based On Frequency Domain In PD Location Of Substation

Substation is an important part of the power system, reliable operation of substation is the basic guarantee of safe and economic operation for the power system. Partial discharge(PD)is one of the important reasons causing power equipment insulation degradation, and it is an important symptom of insulation status in equipment. It is meaningful to detect and locate partial discharge in the whole substation. Based on passive location theory, electrical measurement and electromagnetic analyzing software, the ultra-high frequency(UHF)method used in substation for PD location was studied in this paper.In this paper, the propagation characteristic of electromagnetic wave emitted from PD is studied based on the finite differences time domain method by building a suitable substation model. The results show that the mounting height of Sensor array should 3m higher than that of the bus in real substation, and the power equipment in the substation can lead to amplitude attenuation and time delay of electromagnetic wave, but the impact is very small which hardly influence the PD location in substation. Electromagnetic wave which is emitted from PD occurring in equipment with large energy can transmit to the receiving device through the connectivity gap in the shell, achieving PD location which occurred in the equipment.A new time difference algorithm based on multi-sample signals and frequency domain is proposed in this paper, including its principle and formula. The time delay of multiple sensors was obtained with high precision. This method has a very good anti-interference performance and has proved to be effective to solve the problems of the initial pulse of the PD signal is small and blurry, the time domain method can hardly be applied effectively and will induce rather big errors.Build a three-dimensional coordinate system according to the structure of substation, and start to monitor PD from power equipment in substation received by the experimental platform which was set up early in the substation. First uses transformation of"relevant-shift-superposition"to obtain a statistical signal from a large amount of PD samples received by the sensor array, then adds the time window to extracting the wave top time of statistical signal,by which can improve the similarity between signals of different channels and thus improve the accuracy of time delay .PD location in a substation can be realized with the error in 3 meters by combining the new time difference algorithm which is based on multi-sample signals and frequency domain with genetic algorithm. The research improves the safe level of the substation and ensures the safe operation of power system.