Design of the sensor on alternating electric field is presented.Principle analysis and theoretical derivation are developed.On this basis

the device of electric field measuring is produced.Comparing with the standard instrument

the device is used on 500 kV transmission line and 220 kV substation switching interval and the measured results show that the device has good linearity at 1 kV/m field strength above

and measurements has great relevance comparing with PMM8053

and it has better anti-interference and stability.So the device is suitable for monitoring the frequency electric field in power system for a long time.