By Alex Neumann, Head of High Voltage, ORE Catapult
Subsea cable failures remain one of offshore wind’s biggest headaches, continuing to account for the bulk of insurance claims made by our sector. A failure can arise from minute defects, but can spiral into big cost consequences and months of lost generation, investigation and repair work.
Induced currents and water ingress, for instance, can accelerate ageing of components within cable systems and lead to premature cable failure. The cost of repairing a subsea cable can reach £2-5 million per km, so a fault, such as a cable short-circuit, could prove costly for developers.
Ensuring that hidden design or material flaws in cables are caught before installation is the mission of my team at our UKAS-accredited facility located in ORE Catapult’s National Renewable Energy Centre in Blyth. If a cable fails a test in a warm, dry laboratory (albeit subjected to a variety of stresses!), it will not withstand the extreme loads and harsh conditions experienced subsea.
This role is crucial for cable designers, researchers and manufacturers who are seeking to improve their designs and bring new innovations to market. Cable customers need to be aware that it is their role to specify appropriate test regimes above the standards’ requirements. Meanwhile, the research we conduct for owner/operators provides understanding of the root causes of failures, as well as directly furnishing the insurance community with intelligence to support claims settlement.
Cable qualifications – fit for purpose?
The process for truly testing if a cable is fit to deploy has to go beyond official standards and qualifications. Compliance with these is a bare minimum, in my view. I argue that a cable can only be considered gold-plated for offshore installation once a more rigorous set of criteria are met.
At this year’s Cables 2020, I will be leading a roundtable to discuss precisely this issue. I will be ready to answer questions on the techniques we currently apply to cables in our test regimes. These include accelerated ageing of cables, thermal stability testing and a variety of forensic investigations that include such wizardry as heating insulation in silicon oil, rendering it transparent and revealing the flaws contained within.
I’ll also be keen to emphasise the benefits of knowledge-sharing in the industry: testing individual cable designs is one thing, but without greater transparency on why cables fail in the field, we will not progress as an industry. You can find out more details about our newly launched ELECTRODE programme, led by my colleague Charlotte Strang-Moran in her recent blog, as she builds the world’s first database of offshore wind cable failure data.
Alex is leading the Cables 2020 Problem Solving Roundtable on Cable Design, Test and Manufacturing (13.30-14.40, Tuesday 24th November).