Electrical Tree Growth Behavior Under AC and DC High Voltage in Power Cables

Abstract

This work investigates the impact of an applied AC and DC high voltage on the electrical tree behavior in extruded cross-linked polyethylene (XLPE) insulation based on simulation and experimental validation. Extensive partial discharge (PD) testing methods are being implemented for high voltage cables under AC voltage for monitoring their condition. However, these PD testing methods cannot be utilized for power cables under DC voltages. DC voltages is considered in this study because of the rising implementation of HVDC cables worldwide. Therefore, it is of paramount importance to study the PD behavior originating from defects under DC voltages. Hence, classifying and diagnosing the defects taking place becomes crucial. In this paper, a 3D finite element analysis (FEA)-based modeling is considered to study the electrical treeing behavior using an embedded needle electrode in the XLPE insulation. The experiment entails PD tests with different applied high DC voltages (2.5, 5, 10, 11, and 12 kV) to study the impact on the initiation of PDs and ultimately tree growth. PD measurements were also investigated under AC voltages (7.1, 9.9, 11.3, 12.7, 14.1, and 17 kV) to compare them with PD results obtained with the applied DC voltage. The time-resolved partial discharge (TRPD) patterns are acquired for classifying the severity of the defect present in the XLPE insulation.