Research On On-line Fault Diagnosis System Of Capacitive Type Equipment

In recent years, with the development of the economy and people's living standard, people have a higher requirement on the quality and reliability of electricity and electric power equipment has developed towards larger capacity and ultrahigh voltage. Ensuring the stable operation of power system, power equipment and safety of the operations staff has been an important target for electric power enterprise. More than half of the electrical equipment in substation and power plants are capacitance type electric power equipment. If there is capacitive power equipment insulation fault, power equipment and the safety of the operation personnel will be under serious threat. Therefore, it is very necessary for insulation condition online monitoring of power equipment.Dielectric loss factor tan ? reflects the insulation level of capacitance type equipment. Insulation of the electric power equipment can be easily known through tan ?, therefore, tan ? can be used to measure the insulation of the electric power equipment to ensure safety and stable operation of power system.Firstly, this paper summarized the related measuring method, domestic and international technology of electric loss factor and analyzed the application situation. In view of the stability and precision of the measurement of the dielectric loss factor, researches of dielectric loss factor of capacitive type equipment at substation was carried out, and an insulation online monitoring system based on hierarchical distribution principle of capacitance type equipment was developed.The system mainly contains signal acquisition unit (SU), which is used to extract the weak grounding screen at the end of the current signal, then the acquisition unit was designed based on the principle of capacitance pressure; a mixing protection unit based on discharge tube and varistor was used to the protect the secondary system. And the distributed data acquisition unit based on RS485 bus was realized. For software design, bundled software for on-line insulation monitoring system equipment was developed, and adopted the modular design idea. Graphic and model integration monitoring system is developed, and the system modules are independent from each other, on the need of maintenance and upgrade.This paper proposed the improved algorithm by analyzing the defects of the conventional algorithm and the accuracy of the algorithm is verified by simulation and experiment. The hardware and software system were optimized, the signal parameters becomes more accurate and stable, the graphics interface was more intuitive and accurate. The system would meet the requirements of on-line fault diagnosis system of capacitive type equipment through field test.