New project aims to improve protection against subsea cable faults

A new project to design a system that detects and prevents high voltage insulation faults in subsea power cables for offshore wind farms has been awarded funding by the UK Department of Energy and Climate Change (DECC) Offshore Wind Component Technologies Development and Demonstration Scheme.

As part of the nine month initiative, UK company High Voltage Partial Discharge Ltd (HVPD) and power transmission and distribution outfit Alstom Grid will join forces with Glasgow Caledonian University and the University of Strathclyde to focus on condition monitoring for high voltage direct current (HVDC) cables and interconnectors.

HVDC cables are now seen as particularly important because they will provide the backbone of the proposed EU electricity transmission 'Supergrid' - set to play an essential part of Europe's strategy of meeting the targets set out in the Kyoto Protocol and the European Plan on Climate Change of generating 20 percent of the EU's energy consumption from renewable sources by 2020.

As Malcolm Seltzer-Grant, Senior Development Engineer at HVPD, explains, the installation of HVDC infrastructure has already started as a step towards achieving the required expansion in offshore wind generation at distances further from shore - and several companies are currently developing and proving the technical capability of new HV AC/DC converter hardware and export cables.

The new collaborative project will develop and trial an OLPD (on line partial discharge) condition monitoring system for in-service HVDC networks to monitor HVDC converters and HVDC cables. The first phase of the initiative, to develop and test an alpha system, has already been completed and Seltzer-Grant reveals that laboratory testing to 'improve the understanding of partial discharge under DC stress,' as well as the development and demonstration of a beta HVDC-OLPD system is now underway.

"There is currently no suitable state and condition monitoring system available in the market for these critical HVDC links. The proposed new innovative HVDC-OLPD monitoring system will use on line partial discharge (OLPD) detection," he says.

"This will be combined with other condition monitoring modules to provide an early warning system against incipient electrical and thermal insulation faults and to support direct preventative maintenance interventions, addressing the emerging need to provide a comprehensive health and condition monitoring system for HVDC links," he adds.

Selzer-Grant points out that, when finalised, the scope of the newly developed HVDC OLPD monitoring system will also be expanded to include the state and condition monitoring of the connected AC/DC converter technology.

"The new system is expected to revolutionise the fault finding and early warning system for HVDC cable operators," he says.

"Operating as an intelligent assets management tool it will also help improve electricity supply security," he adds.