Cause of Heathrow shutdown fire remains unknown, says system operator

Investigators person failed to find the basal origin of the substation occurrence that unopen Heathrow airdrome successful March, six weeks aft the authorities ordered an “urgent” investigation.

A preliminary study from the National Energy System Operator (Neso) ruled retired immoderate suspicious enactment down the outage which chopped powerfulness to the airport, affecting much than 1,350 flights and astir 300,000 passengers.

But the state-owned assemblage admitted that the “root origin of the fire”, which besides near astir 67,000 homes without power, inactive “remains unknown”.

The strategy relation has promised to proceed its probe into the attraction past and plan of the 57-year-old powerfulness substation successful westbound London that caught occurrence successful precocious March to found whether it was gathering its ineligible requirements.

It volition besides analyse the configurations of the airport’s backstage energy network, which took hours to repower aft the substation outage, adjacent arsenic 2 adjacent substations continued to run arsenic normal.

Heathrow took a further 7 hours to unfastened aft the powerfulness was restored, according to the report, meaning flights were disrupted for astir 24 hours aft the occurrence broke retired connected 20 March.

Neso said a dedicated squad reviewed much than 600 pieces of grounds from the companies progressive successful the incidental to pass its interim report. It expects to people a last study by the extremity of June.

In precocious March, Ed Miliband, the vigor secretary, ordered the strategy relation to undertake an “urgent” probe into what happened and supply its archetypal findings wrong six weeks of the blaze.

On Thursday, helium said: “We present await the afloat study to recognize what happened and larn lessons to fortify UK vigor resilience and support our captious nationalist infrastructure.”

Heathrow airdrome said the study raised questions for National Grid – the proprietor of the substation that caught occurrence – and Scottish and Southern Electricity Networks (SSEN), liable for powerfulness organisation successful the area.

A spokesperson for the airdrome said: “Further clarity connected however the occurrence started and wherefore 2 transformers were subsequently impacted tin assistance guarantee greater resilience for the UK’s vigor grid moving forward.”

The vigor companies progressive successful the powerfulness outage volition besides look an enquiry by the industry’s regulator, Ofgem, which is liable for approving the investments and revenues of energy web operators.

Heathrow volition besides motorboat an interior probe into its resilience, led by Ruth Kelly, the erstwhile caput of authorities for transport and autarkic committee subordinate of the airport.

Executives from the vigor and hose industries were summoned wrong days of the outage to appear earlier parliament’s cross-party transport prime committee.

Heathrow’s main executive, Thomas Woldbye, apologised for the disruption. He told MPs that a powerfulness outage connected this standard had been seen arsenic a “very debased probability event” and the airdrome had paid for a “supposedly resilient” supply.

A spokesperson for National Grid said the institution would proceed to enactment intimately with Neso successful its investigation, and looked guardant to the afloat report. SSE was approached for comment.