Partial discharge characteristics of NYCY low-voltage cables

Detecting possible faults in low-voltage cables is a complex task, because the construction of these cables allows various partial discharge sources to incept even at test voltage. Experiments have shown high partial discharge magnitudes and activity even in new cables. This paper describes the attempts to detect faults in 0.6/1 kV PVC insulated (NYCY type) cables by characterizing the PD phenomenon in new cables and comparing them with that in damaged cables. For this purpose the partial discharge signals were detected by a high frequency current transformer and recorded with a digital oscilloscope. Experiments were performed at different voltage levels and durations. The recorded signals were processed in order to examine several different properties like magnitude, repetition rate and statistical operators characterizing the phase resolved pattern and the pulse height distribution.