The Research And Development Of On-Line Monitoring System For Switchgear Partial Discharge Based On DSP

Switchgear is a very important equipment in power system. In the manufacturing process, insulation defects will inevitably occur, which can cause partial discharge. Partial discharge can cause further deterioration of insulation.This will cause insulation failure to threat the safety and operation of power system. So it is of great importance to detect partial discharge. There are many kinds of methods to detect partial discharge by detecting the physical or chemical phenomena generated by partial discharge to achieve the purpose of detecting partial discharge. This thesis uses the ultrasonic method to detect partial discharge in switchgear, analyzing the reasons of partial discharge and the mechanism of generation, propagation and detection of ultrasonic wave. On this basis, the structure and principle of the switchgear partial discharge monitoring system is presented.The processor of this system is one chip of DSP named TMS320F28335. This chip has the characteristics of high processing speed, high precision and strong computing power. Analog bandpass filter circuit is designed based on MAX275 to filter the ultrasonic signal to reduce the required minimum frequency of sampling. The A/D module of TMS320F28335 is configured to convert ultrasonic signals to digital signals that can be processed by DSP. The performance of the A/D module is tested by collecting analog signals with different waveforms and frequencies, and then to analysis the impact of signal truncation by actual. Aiming at the problem of the interference of the partial discharge ultrasonic signal, FIR digital filter is designed to filter the digital discharge signal. And the application of FFT noise reduction algorithm in partial discharge ultrasonic signal denoising is simulated by MATLAB, analyzing the noise reduction performance. Ultrasonic signal after filtering is calculated and processed by FFT to analyze the frequency and amplitude of the signal and then record discharge trends to monitor the partial discharge of switchgear. Aiming at the problem of large amount of data involved in the data processing algorithm of the monitoring system, use the external RAM memory to expand the data storage space. The external FLASH memory is used to store the relevant information of the partial discharge, providing live viewing for the technical personnel. Discharge alarm circuit and display module of discharge intensity is used to alarm discharge and display discharge intensity. Through the ethernet communication circuit based on W5500, the communication between monitoring system and host computer is realized to monitor partial discharge of switchgear remotely.The design of algorithm and hardware system studied in this thesis will provide knowledge reserve for the development of small partial discharge monitoring system, having important practical significance to guarantee the normal operation of the switchgear.