Recently

the bypass faults due to several high constant of unbalanced current of capacitor banks has occurred in a 500 kV series compensating station in the power grid in China. In this paper

the cause and type of the fault are judged by way of studying operation mechanism and protection mode of unbalanced current of capacitor bank of the series compensation station in combination with fault record analysis. The verification is made by the fault simulation. Then

the fault capacitor unit is successfully detected by the inter-electrode DC voltage test in accordance with the characteristics of the fault type and verified by disassembly inspection. The actual results at site show that this method can effectively troubleshoot the transient recovery faults mentioned in the paper

and provide reference for operation and maintenance personnel to deal with this type of faults in the future.