In this paper

the faultof low secondary voltage of capacitor voltage transformer（CVT）in pumped storage power station is introduced firstly. The analysis and calculation is performed according to the structure feature and operating principle of the capacitor voltage transformer

judging preliminarily that the fault is due to breakdown capacitive component of the capacitor voltage transformer. It is found after disassembly inspection and test analysis of the equipment that four capacitive elements are breakdown. The correctness of the analysis is proved

the fault is found out

the fault is eliminated and power supply is recovered after replacement with new capacitor voltage transformer and the secondary power supply is recovered. Finally

the suggestion and preventions are proposed to the operation and manufacturer for reference.