The traditional detection methods for power capacity would be carry in off line condition

that affect the power transmission. Exist on line detection methods for power capacity main in deal with the capacity’s volume and .Obviously

the gotten result would be lag behind the fault which had happened. According to the general faults of HV power capacity in power systems

authors analysis the reasons of partial discharge（PD） in fault

get the conclusion that the faults of PC generally accompany with PD

and PD is in the initial phase of the faults. Authors analysis the possibility of detection for these PD and find ways

design a kind of detection for PD with PC.