The abnormal secondary voltage of the capacitor voltage transformer（CVT）is mainly caused by such factors as breakdown of capacitor element and short circuit of winding etc. In this paper

it is found from a real CVT which has lower secondary voltage and through related analysis that insertion of copper lead sheet in the series of the capacitor element of the product causes the connection point of outlet sheet and aluminum foil to become into a weak point. Slight change of even pole sheet structure

such as weak process control in the insertion or burr

can cause partial field strength concentrate and is easy to lead to breakdown. As for the abnormal low secondary voltage

the operation unit shall strengthen monitoring and the manufacturer is also suggested to improve the structure of outlet lead

strengthen process management and control so to prevent the similar fault and assure stable operation of power system.