High voltage electricity network internal and external overvoltage comprehensive on-line monitoring apparatus and method

An on-line monitoring device and the method for the over voltage of the high tension electricity relates to the monitoring device and the method for the 110-500KV high tension electricity net. The device includes the voltage sensor, the matching and the protection circuit, the signal pretreatment circuit, the trigger circuit, the data collecting card, the working power supply and the industrial controlling computer. The invention can work for long time in the condition of 110-500KV high-pressure main frequency AC, but the monitoring precision can reach +-1%.