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UK power cut: Ofgem launches probe into mass blackout after National Grid finds outage was caused by lightning strike

Ofgem will probe a mass power cut which hit the country earlier this month after an initial report stated they were sparked by a lightning strike.

It comes after an initial report from National Grid into the outage gave its in initial explanation for the blackout, which saw almost one million electricity supplies go down.

National Grid said in an interim report that a lightning strike on a transmission circuit, followed by "two almost simultaneous unexpected power losses" at two power plants, caused the disruption on August 9.

The outages at Hornsea off-shore windfarm and Little Barford gas power station occurred independently.

Commuters were plunged into darkness(PA)
Commuters were plunged into darkness(PA)

This scale of generation loss meant that the level of "backup" power required under the regulatory standards was insufficient to cover the loss, the report from National Grid Electricity System Operator said.

As a result, the system automatically disconnected customers on the distribution network - resulting in about five per cent of electricity demand being turned off to protect the other 95 per cent.

The power outage affected large areas of the UK (PA)
The power outage affected large areas of the UK (PA)

The interim report said: "Two almost simultaneous unexpected power losses at Hornsea and Little Barford occurred independently of one another - but each (was) associated with the lightning strike.

"As generation would not be expected to trip off or de-load in response to a lightning strike, this appears to represent an extremely rare and unexpected event."

There were huge crowds at train stations due to delays (PA)
There were huge crowds at train stations due to delays (PA)

The regulator Ofgem said its investigation into the power cuts would examine the grid's requirements to hold sufficient back-up power to manage loss of generation supplies, how generators met their obligations with respect to the transmission fault and whether distribution network operators complied with their obligations.

The blackout prompted travel chaos as trains were massively disrupted, with some stuck stranded on rails due to the outage.

While traffic lights were also out in some areas and airports were also impacted.

Almost one million supplies were out due to the cuts.