Ofgem has opened an investigation into National Grid after the substation fire on 20 March that led to the closure of Heathrow, as a review found that the root cause of the fire was a “preventable technical fault”.
This caused a “catastrophic failure” on one of the transformer’s high-voltage bushings at the North Hyde electricity substation in Hayes, west London.
The energy regulator said it had launched an official enforcement investigation into National Grid Electricity Transmission (NGET). It will examine the incident, its causes and take further action as necessary.
The final report from the National Energy System Operator said: "This review has seen evidence that a catastrophic failure on one of the transformer’s high-voltage bushings at National Grid Electricity Transmission’s 275kV substation caused the transformer to catch fire.
"This was most likely caused by moisture entering the bushing, causing an electrical fault. An elevated moisture reading in the bushing had been detected in oil samples taken in July 2018 but mitigating actions appropriate to its severity were not implemented."
Ofgem will review whether NGET complied with the relevant legislation and licence conditions relating to the development and maintenance of its electricity system at North Hyde.
The regulator will also commission an independent audit into NGET’s critical assets and their status to figure out whether the failings at the North Hyde substation were a one-off or more systemic across National Grid.
Japanese stocks fell after Donald Trump threatened 35% tariffs on Japanese imports, in an attempt to pressure Tokyo into making concessions during negotiations that he described as “very tough”. The Nikkei fell by 0.6% after paring earlier heavier losses.
Yesterday, markets shrugged off the US Senate passing Trump’s “big, beautiful bill”, as investors stayed glued to the outlook for US interest rates and trade deals, ahead of the US reimposing tariffs on 9 July. The agenda • 10am BST: eurozone unemployment for May • 1.15pm BST: US ADP employment change for June • 3.15pm BST: ECB president Christine Lagarde gives speech
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