Estimation of the Partial Discharge Inception Voltage of Low Voltage Cables

There is an increasing interest in the diagnostics of low voltage cables that serve safety systems of nuclear power plants. Besides the assessment of the lifetime of the cable material in bulk, the detection of local defects is also important, as these can result in function loss of the cables in case of critical events. Partial discharge measurement is widely used for the condition monitoring of medium and high voltage cables, but its application on low voltage cables is a difficult task, as these cables are not designed to be partial discharge free at their test voltage. In the present paper estimation of the inception voltage is given mainly for intact cables based on electric field calculation. Cables of different design are studied. The effect of the number of cores and their cross section are investigated through electric field calculations. Finally, the calculation results are compared with measurements.