To prediction on the effect of insulator damage, the significantly on high voltage insulator surface deterioration will be indicated the details when investigate not only on amplitude of LC, but very significant necessary to investigate with LC signal specially have to concentrate on distortion of the its wave shape like as total harmonics distortion. It will completely if investigate the loss characteristics dielectric of insulator with amplitude LC and harmonics component content on LC signal. Furthermore, physical change of insulator surface is easily and necessary to observing in order maintenance transmission line or substation.