Study On The Setting Calculation And Fault Analysis Of High Voltage Shunt Capacitor Banks

High voltage shunt capacitor compensation method is the most simple and economic method, the capacitor is related to the safe and stable operation of power system. However, the capacitor faults happen frequently, the influence factors of capacitor failure are relatively complicated, it is difficult to find the reason of capacitor faults. Therefore, it is important and practical to analyze and properly set capacitor units’ unbalance protection.According to the actual configuration, this paper combined theoretical research with simulation calculation, and on-site analysis method, to study high voltage shunt capacitor groups’ unbalance protection. Therefore, we obtained the calculation method for some kinds of protection ways and the alteration voltage and current in different fault conditions. Meanwhile, how to choose the series inductor is also given. The following conclusion has been obtained.Firstly, this paper have studied a variety of connection structure of capacitor units and fuse wiring methods, then four kinds of common protection connection modes are analyzed and deduced so that calculation formula of different forms are given, and the initial unbalance value are estimated.Secondly, simulation models of different connection structure are built up based on the PSCAD/EMTDC software. This paper found that overvoltage gain on failure component and also unit increased accordance with the number of fault elements. Tolerance between two phases had great impact on the initial unbalance value. The correctness of the theoretical calculation were verified by comparing it with the simulation values.Thirdly, the selection rule of shunt capacitor reactance rate were analyzed, we found that using 4.5%-5% series inductance rate cannot suppress the 5th harmonic effectively. This paper made theoretical research on harmonic amplification principle and harmonious resonance calculation, also studied branch current response against different series reactance rate and illustrated the series inductance rate selection method by sample calculation. Besides, based on the software Lab VIEW, the author developed a software with which to calculate the setting value of common protection and resonance estimation.Finally, in view of the capacitor banks’ unbalance protection tripping frequently, capacitors statistics about a city were classified, taking the representative capacitor group as the object, through simulation and experimental to analyse the causes of frequent tripping, the research concluded that the low setting value and excessive initial unbalance value are the most likely reason caused tripping.At last, the fault capacitor were dissected, for analysis the internal structure.In summary, the research conclusion complete the unbalance protection calculation of shunt capacitor, explain the influence of the initial unbalance, also provide a new idea for the series inductance rate selection.This work has some reference value to the protection of capacitor banks.