As for the abnormality of secondary voltage of 330 k V capacitor voltage transformer（CVT）in operation

it is checked clearly by way of site inspection and disassembly at factory that the cause for such abnormality is due to insulation strength reduction of arrester for primary part protection of electromagnetic unit. The normal inspection and test result of the CVT capacitor and electromagnetic unit are analyzed and compared. The judgment method and conclusion are given. Also elimination method and procedure on abnormality of secondary voltage of CVT are proposed;corresponding suggestion are provided;and the specific measures on strengthening condition monitoring of CVT in operation in network are also proposed.