Figs. 7 and 8 show the order harmonics component on LC
signal at the same current from different excitation voltages.
We have found that the fundamental LC, I1, at frequency of
50 Hz is the highest amplitude. It means that I1 is dominant
current component of LC and the percent of total harmonics
distortion which calculates from equation (1) is clearly
shown on the HVAC alternate with impulse voltage
excitation. All results and discussion revealed that severe
effect of insulator were resulted from an excitation of
impulse more than high voltage AC excitation voltage.