Series reactance rate is the important part of the reactive power compensation capacitor, if which of poor choice may cause occurrence of resonance between capacitor and the system, affecting the safety of equipment and system stability. In this paper, with the actual project cases integrated, according to the power capacitor switching tests and field tests on one electrical substation, we got series reactor parameters in reactive power compensation capacitor do not match is the direct cause of capacitor fuse explosion. Proposed a concept that in the case substation has current limiting reactor, the capacitor design in addition to select the appropriate series reactance rate, should be considered the equivalent series reactance. What's more, according to the actual situation, the corresponding solutions are given and the harmonic situation in shunt compensating branch when capacitor bank in different series reactance rate are analyzed.