A Novel On-line Differential Technique for Partial Discharge Measurement of MV/HV Power Cables

Insulation deterioration is an increasing problem because of the ageing of high voltage power cables and current deregulation circumstance. Partial discharge (PD) measurement has been used for insulation assessment for many years. It has been widely adapted as an insulation diagnosis tool for factory acceptance, commission and maintenance purpose. However PD measurement carried out on site is affected by strong electromagnetic interference (EMI), which makes accurate PD measurement very difficult. The differential circuit has been applied for common mode noise rejection purpose for many years. This paper presents a novel software implementation of the differential circuit to handle the interference. The conventional hardware differential circuit technique is compared with this software-based technique in many aspects from short length to medium length distribution power cables. Some difficulties with the differential technique as applied to PD measurement are also discussed and investigated in this paper