Dielectric Integrity Test- A Tuned Circuit Approach

Dielectric integrity tests usually performed to check the dielectric strength of an electrical insulation are power frequency withstand, lightning impulse (LI) and switching impulse (SI) withstand voltage tests. These standard testing techniques involve subjecting the insulation to over voltages which are several times the rated voltage. Incidentally, breakdown of insulation occurs mainly due to stresses in the insulation due to free volume charges and thermal agitation. It is observed that the stress and heat produced in the insulation of an alternating voltage of comparatively lesser magnitude at high frequencies can be achieved across the insulation i.e., at certain levels the volume charges and thermal agitation due to dipole spinning increases, leading to lower breakdown values. This concept may be effectively utilized as a supplementary testing technique where the need for testing the dielectric integrity of apparatus in laboratory with limitations on test voltages arises. A tuned high frequency high voltage (HVHF) generating setup has been proposed for conducting an exhaustive experimental study and analysis on the frequency response of air and transformer oil test set up with different electrode configurations. Impulse voltage tests for breakdown have also been carried out for the purpose of comparison of the proposed scheme