Combined power quality and condition monitoring of offshore networks

The authors present a paper detailing their experiences (over the past 5 years) in the insulation condition monitoring of land-sea export cables and subsea array and platform interconnection cables in the UK offshore renewables and oil & gas industries. The paper focusses on the use of partial discharge (PD) testing to detect and locate pre-fault PD activity and also the use of time domain reflectometery (TDR) techniques to provide a `fingerprint´ of the cables and to help pinpoint cable faults after they have occurred. The paper will also discuss a `holistic´ monitoring approach, combining a number of condition monitoring technologies, to achieve necessary information to support improved CBM. For the HV networks, power quality monitoring should be integrated with the monitoring of partial discharge (PD), cable sheath current and weather data (i.e. wind, wave or tidal energy resources, power flows and occurrence of overvoltage/overcurrent conditions), with the further cross-correlation of all of these condition and state parameters, in order to allow for the early detection, faster identification and efficient resolving of faults, failures and other problems during the operation. The purpose of such an integrated monitoring platform is therefore, to provide an advanced `early warning´ against insulation faults to enable planning of preventive or corrective maintenance to be carried out and to avert unplanned outage.