Characterization of Cavity PD Under Impulse Voltage in Polyethylene Insulation

Understanding PD (Partial Discharge) phenomena under impulse voltage is important knowledge for the improvement of reliability of HV (High Voltage) equipment. PD in HV equipment can cause severe insulation deterioration resulting in breakdown, production loss and high cost of repairs. HV equipment insulation can fail due to PD activities which are initiated by impulse voltages such as lightning and switching. The latter has been exacerbated by load shedding switching operations in South Africa. PD detection under AC (Alternating Current) frequency voltage conditions is well developed, however there is inadequate knowledge in PD detection and diagnosis under non-power frequencies. The challenge is to enable PD detection during impulse voltage, due to the overlaps between the impulse voltage and the PD frequencies. In the present work, balanced PD detection circuit is implemented to suppress impulse voltage interference for the purpose of detecting cavity PD under impulse voltage. The measurement results show that PD pulses occur on specific locations of the impulse test voltage waveform and is consistent with similar results in the literature.