Investigation on partial discharge inception voltage and discharge pattern of simulated defect cable system

Abstract

This paper presents an investigation on partial discharge (PD) inception voltage and PD pattern of simulated defect underground cable caused by two types of supply voltages such as alternating current and direct current voltage sources. The 50 Hz alternating current (AC) source from test transformer represents the nominal voltage supplying in power system while direct current (DC) source from rectifier circuit with positive and negative polarities represents a cable usage in DC transmission system. The simulated defect cable was constructed in a cable system consisting of two sets of 10.5 meters long underground cable rating of 6/7.2 kV. The defect as surface discharge was created at the cable joint between two cables. The PD was measured and investigated by commercial High Frequency Current Transformer (HFCT). The PD inception voltage, PD pattern and type were observed under AC and DC supply voltages. Finally, PD location was successfully determined by applying Time Domain Reflectometry (TDR) technique analyzed by the commercial tool and compared with analytical travelling wave theory using oscilloscope. This technique can be applied to practice PD localization of underground cable.