National Grid has said it will "learn the lessons" after nearly one million people across England and Wales lost power on Friday.
But director of operations Duncan Burt told the BBC that its systems "worked well" after the "incredibly rare event" of two power stations disconnecting.
He said he did not believe that a cyber-attack or unpredictable wind power generation were to blame.
Regulator Ofgem has demanded an "urgent detailed report" into what went wrong.
It said it could take enforcement action, including a fine, after train passengers were stranded, traffic lights failed to work and thousands of homes were plunged into darkness during the blackout.
Some train services continued to be disrupted on Saturday morning.
The power outage happened at about 17:00 BST on Friday, National Grid said, with blackouts across the Midlands, the South East, South West, North West and north east of England, and Wales.
Industry experts said that a gas-fired power station at Little Barford, Bedfordshire, failed at 16.58, followed two minutes later by the Hornsea offshore wind farm disconnecting from the grid.
National Grid said power was restored by 18:30 BST.
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But throughout Friday's evening rush hour there was huge disruption on the railways, as police officers were called in to help travellers and delayed passengers were stranded for hours.
Northern Powergrid said the problems had affected Newcastle airport and city's metro system.
King's Cross was one of the worst-hit stations, with all trains suspended for several hours.
The first train out of the station was at 21:30 to Peterborough, and the first long distance service was packed as it left for Newcastle at 22:46.
Passenger Dayna McAlpine told BBC Radio 5 Live her train took nearly 13 hours to reach London King's Cross from Edinburgh - a journey which would normally take less than five hours.
"By hour seven things were starting to get pretty tense," she said. "People were threatening to self-evacuate off the train... Food ran out about five hours ago."
Others on social media reported having travelled for 12 hours, while some rail passengers were stuck on trains until the early hours of the morning.
Some train companies warned the disruption will continue into Saturday morning.
London North Eastern Railway, which runs between King's Cross and the north of England and Scotland, has cancelled some services.
Thameslink and Great Northern said a number of trains did not end up in their correct location on Friday because of the disruption and problems will continue until 12:00 BST on Saturday.