Development Of An Instrument In Partial Discharge Detector Based On Ultrasonic

Electrical equipment are important equipment in power system and power transmission line is the key part of the power system. It has important significant to make fault detection and diagnosis on electrical equipment and power cables, detect the hidden accidents of electrical equipment and power cable in time, prevent accidents, and improve the safe reliability of running electrical equipment. With the continuous improvement of voltage and the effect of the high-voltage and high electric-field, partial discharge will occur in some insulation weaknesses of the electrical equipments and power transmission line. Therefore it has realistic meaning of development a partial discharge detection equipment to realize the on-line detection of electrical equipment and power cables. This issue is raised based on this demand.In this thesis, partial discharge detector based on the ultrasound is researched and designed systematically. It has features of small size, convenient using and portable.Partial discharge detector, which uses the STC89C52 single-chip microcomputer as the core, can complete the detection of partial discharge, high-speed data acquisition and storage, discharge alarming, discharge intensity shows and communication with the host computer, etc. In the hardware design, the issue adopts the idea of modular design. First it chooses the ultrasonic sensor in accordance with the mechanism of partial discharge and the ultrasonic character and its propagation rules. In order to ensure the safety and reliability of the detector, it designs the photoelectric isolation circuit module, which realizes the strong and weak electricity power isolation with the optical transmission method. In the analog signal pre-processing unit and sampling trigger circuit design part, it completes the design of amplifier, band-pass filter circuit, sampling trigger circuit. In the high-speed data acquisition modules part, it mainly completes high-speed data collection and its storage. Because the speed of single-chip can not keep up with the sampling rate of ADC, it designs 20-bit address generator with the hardware to complete the storage of high-speed data. At the same time it completes the design of the discharge display circuit, alarm and reset circuit. RS485 interface realizes the communication with the host computer and ensures the communication distance and the noise immunity. In order to analyze the relationship between the ultrasonic signal and the discharge, eliminate noise interference and accurately extract the partial discharge pulse signal, it introduces the extraction method of discharge signal using the wavelet transform. Finally, it makes prospects at the partial discharge detector and proposes some methods of thinking from several aspects to do further research and improvement of the system.The partial discharge detector can make on-line detection of partial discharge of the electrical equipment and power transmission lines quickly and easily, collect and process the data of the partial discharge signal. Therefore it greatly reduces the outage time and saves reconditioning expense, which has a good application prospects.