The Effect of the Over Voltage on the Stress Distribution at the Terminals of H.V. XLPE Cables

Abstract

The power cables are usually subjected to over voltages from lightning impulses and switching surges, such over- voltages effects are concentrated at terminals of the high voltage cables .The longitudinal and radial stresses through cable terminals are computed by using Schwarz christoffel transformation used for sketching the electrical fields.The investigated cables are of rated voltage 33Kv and 132Kv insulated by cross-linked polyethylene (XLPE).Electrical field sketching at the cable terminals is carried out theoretically by the aids of computer programs. The results give an indication of the maximum stresses occurs in the cables insulation at the terminals and the maximum longitudinal stresses along the cables screen at outer surface of the XLPE insulation. The results show that maximum stress occurred by lightning impulse is found much higher than that of switching operation but the later has longer period. And both are found depends on the polarity of the over voltages and the polarity of the (power/frequency) voltages.Keywords: stress distribution ofover voltage XLPE cables, termination of XLPE cables