Capacitor voltage transformer is to extract voltage by series capacitor and then transformed to be voltage source of meter, relay protection, etc. by transformer. It can make carrier frequency coupled to power transmission line to be used in long distance communication, distance measure, selective line high frequency protection, remote control, telex and so on. Compared to general electromagnetic voltage transformer, it can avoid ferro-resonance caused by iron core saturation of voltage transformer and has advantages in economy and safety.