Protection And Fault Simulation Study Of Shunt Compensation Capacitor Bank

As the main reactive compensation device in the power grid, Shunt capacitor banks aregenerally used in the low voltage bus of the main transformer in the substations. The capacitorfaults in the substations occurs frequently, causing large economic losses to the power supplyenterprises, pose a great threat to the normal operation of power grids. The faults of the shuntcapacitor banks are related to the capacitor manufacturing level, the operational conditions,the configurations of the devices to control and protect, and the reliability of the devices tocontrol and protect. Besides, the operation state of the power grid has a certain impact on thecapacitor faults. A correct analysis of the capacitor faults, and the reasonable protectionconfiguration of the capacitor bank are of great significance to ensure the reliability of thegrid operation and improve the economic efficiency of electricity enterprise and society.This paper analyzes the equipment and operational requirements of the shunt capacitorbanks. According to the actual capacitor banks operation of the substations in some region, astatistical analysis of the shunt capacitor banks faults is made. The principle and scope ofapplication of the unbalance protections for capacitor banks are analyzed. The reasons toselect the connection mode of capacitor banks and the performance comparison of the modesare also discussed in this paper.For the protection configuration of10kV shunt capacitor banks, according to theprinciple of setting, Two common unbalance protection settings are derived, and thecorresponding setting formulas are given, which are as the theoretical basis, the software of10kV shunt capacitor banks unbalance protection setting is written.For35kV high-capacity shunt compensation capacitor banks, making60Mvar capacitorbanks whose capacitors are within the fuse as an example, This paper describes somecommon protection program for the35kV shunt compensation capacitor banks. Thesimulation models of each kind of protection program are made. The voltage and currentdistribution characteristics after the failure of the capacitor component breakdown, and theunbalance voltage or current in the protection are simulated and calculated in theEMTDC/PSCAD application. Finally, the technical and economic indicators of the programsare compared, and the best protection program is given. According to the statistical analysis, it is found that the main failure of the shuntcapacitor banks is the capacitance value change, which is also namely capacitor componentbreakdown failure. The faults of the capacitor banks are related to the connection mode ofcapacitor banks, operating environment temperature, the product quality and other factors.According to the simulating calculation and comparative analysis of the protection programsof35kV shunt capacitor banks,35kV and60Mvar capacitor banks should not use the split-starunbalance current protection mode, and the best protection mode is the bridge phase currentdifferential protection, and the voltage differential protection can also be used.