According to a multiplex-translating fault between the 500 kV lines and series capacitor compensation equipments， the operations of series capacitor compensation protection and line protection during the fault are analyzed. The analysis results agree with the recorded data and protection operation reports， it shows that the spark gap might have something abnormal during the fault. After analyzing operation principles of the spark gap， it is found that the serious damage of the capacitors in short time is caused by failure to trigger spark gap. By analyzing connection mode and withstand explosion capacity of the capacitors， it shows that two or three-in-parallel connection mode might match with requirement of withstand explosion capacity standard. In consideration of the characteristic of capacitor internal fuse， the damage reason of the capacitors is described. Finally， some design proposals for series capacitor compensation equipments is proposed.