The Analysis Of The Sensitivity And Reliability Of The Capacitor Bank Protection

In the power system, there are varieties of ways to adjust reactive power, and shunt capacitor bank is the most simple, economic, convenient and flexible. In order to insure that the capacitor can be in service safely and reliably, we set a variety of protection schemes according to the way of the wire connection. First this paper describes the usual connections of shunt capacitor banks. And then introduces the principle of variety of the fuses for the problem of that the mix using of internal fuse and external fuse. At last, the paper provides some suggestions for the protection configuration parameters based on the calculation and analysis of the unbalance voltage and unbalance current in the protection of shunt capacitor bank.There are various incidents of the capacitor bank in recent years, so the capacitor protection still has much to research. But there have not been a unified opinion about the problem of internal fault of shunt capacitor bank, and it is also still a problem in nation standard. With the isolation of the capacitor elements, it will cause overvoltage on remained healthy capacitor units and elements in the faulty phase. And it becomes the contradiction and key point of that the capacitor bank weather could continue to work and maximum its used time. Because the fault current or voltage variation is very small, so the setting value is difficult to determine, so the analysis of reliability and sensitivity of different voltage levels of the various protection methods is also one of the key issues. The paper also provides a method of a faulty phase detection based on the research and calculation, so as to reduce maintenance time of shunt capacitor banks. Meanwhile, this paper make improvement of setting algorithm based on the analysis of the sensitivity of protection, and it reduces the influence of the inherent unbalance on the setting value of protection effectively.Finally use PSCAD/EMTDC to have a simulation to verify the influence of the inherent unbalance which caused by tolerance to the motion and the reliability. And provide some suggestions combined with the simulation results of the different voltage level of protection.