Analysis of HV cable faults based on correlated HFCT and IEC60270 measurements

This paper presents simultaneous measurements using three methods of partial discharge detection on 15kV high voltage cable sections with artificially created fault geometries, namely a semiconductor point and a large and small metal particle embedded on the insulation. These faults are simultaneously investigated using two 20MHz bandwidth HFCTs and an IEC60270 system. The peak value of one of the HFCT signals is measured to produce φ-q-n pattern plots and the other is used to generate an HFCT electromagnetic interference (EMI) frequency spectra. IEC60270 φ-q-n patterns are also simultaneously produced for comparison. Measurements are synchronised in time and trended allowing comparisons between the methods to be investigated for changes in characteristic behaviour. Correlations between primary statistical parameters of the φ-q-n patterns and identified signature HFCT EMI frequency band changes are highlighted in order to show the key distinctive characteristics for the faults considered. It is also shown that by understanding and correlating simultaneous HFCT EMI spectra and HFCT peak φ--q-n pattern measurements it may be possible to determine, with some confidence, the nature of the fault rather than relying on a direct contact IEC60270 measurement system.