Correlation of IEC60270, HFCT RF spectra and HFCT PQN patterns for HV cable fault

This paper presents experiments carried out on sections of typical subsea 11kV HV cable with an artificially created fault geometry, namely a semiconductor point fault which is then compared to a clean termination (no point fault) with the fault removed. Partial Discharge (PD) measurements using IEC60270 phase-charge-number (PQN or (Φ-q-n), peak High Frequency Current Transformer (HFCT) (Φ-q-n, Low Frequency (LF) HFCT RF EMI and radiated Ultra High Frequency (UHF) RF are undertaken. All measurements are synchronised in time allowing correlation between the produced Φ-q-n and RF spectral measurements over time to investigate changes and possible characteristic behavior between the four methods. Few publications have investigated the correlation of IEC60270 Φ-q-n, HFCT Φ-q-n, RF EMI spectra from a LF HFCT and radiated (UHF) RF spectra for potential PD cable fault geometries. Initial results demonstrate that a semiconductor point fault condition produces different PD characteristics in both the frequency domain and Φ-q-n domain. This has the potential for higher discrimination ability between this fault geometry and clean termination when both systems are utilized. This could also show RF EMI HFCT measurements to be comparable to and potentially replace the IEC60270 method.