Study On Power Supply Of On-line Monitoring Equipment For High Voltage Equipmen

The stability of the power grid is more and more important with the rapid development of electric power industry. Since power failure often produces serious results, online monitoring of the power devices is necessary. However,a broad distribution of the grid makes it difficult. Therfore, it is vital to obtain power from outer area and supply energy for monitoring devices. Thus, it is an urgent research nowadays.This paper is based on the previous research of insulator online monitoring by ultra-violet light detecting partial discharge. A method which obtains energy with CT and uses lithium batteries as backup is proposed. This method adopts current transformer which obtains energy from transmission line. And through rectification and filtering, the energy can be supplied for online monitoring devices. Considering the instability of line current, charging-discharging circuit and overcurrent protection circuit are also added. When line current is low, lithium batteries work as backup. When line current is too high, overcurrent protection circuit prevents follow-up circuits being damaged. In the simulated experiment, we recorded the performance of this method in different line current. And we checked its application in the field test.The research mainly includes:①The theory of online monitoring devices and the analysis of its operation circumstance and power characteristic.②The theory of CT and the energy transmission from transmission line. Circuit model of the CT is built. So, it comes to the relationship between output power and load resistance of CT.③The design of CT is optimized including some parameters. Control circuit for energy transmission is designed and tested to meet the specific needs of on-line detection equipment.④The theory of the Battery management circuit and the analysis of its operation process of the charging and discharging.⑤Simulation and field test are both completed to analyze the performance of the CT energy supplying method in long-term operation.The advantages of supplying energy from electromagnetic induction and lithium batteries backup are illustrated in this paper. The experiment shows that devices based on this method can provide enough power even if line current varies in a wide range from 0 to 1000A. It proposes a practical solution for supplying energy for monitoring devices and promoting the online monitoring techniques.