Major Outage

Only two weeks after returning to service from the February-March 2019 land-cable fault, the Western HVDC Link tripped again on 6 April 2019, this time due to a fault on the undersea cable section. Per REF's analysis of 13 April 2019, the latest problem appeared to affect a subsea section of the cable approximately 150 km from Hunterston. The 2,250 MW bipolar HVDC link relies on both cables of the bipole being in service — mass-impregnated paper-insulated (PPL) cables in a bipolar arrangement with no sea- or earth-return path — so a single cable fault takes the entire link out of service. The second 2019 outage was extended in duration, requiring offshore mobilisation by Prysmian to locate the marine fault, recover the affected section, joint a replacement segment, and rebury. By 12 April 2019, constraint costs associated with Western Link unavailability had cumulatively reached £297m according to REF's tally. The recurrence so soon after the February event escalated regulatory and political concern about the link's reliability, contributing to the Ofgem enforcement investigation opened in January 2020.