I worked 40 years in safety and reliability in transportation industries, laterally with ATC. I could tell many stories of power supply disasters in so called very resistant systems. In the Far East I was doing a project in a road control centre. I asked them about power supply resilience and was assured they had all the batteries and generators to make it bulletproof. THE VERY NEXT DAY on entering the centre there were worried looking managers and a long extension lead across the floor leading the back of a server rack. “We had a power failure and had to do that to get it working again”.
In the same country the main and backup power supply went through the same circuit breaker which failed taking down a complete train line.
In UK ATC the last serious power outage was 15-20 years ago. Since then NATS has vastly improved the power systems so, whilst nothing is impossible, I’d be extremely surprised if power was the cause. If it did happen the most likely cause would be maintainer error rather than a straight hardware or software failure in the power supplies. Many of NAT’s recent very occasional issues have been due to software upgrades not going to plan but they are nearly always recoverable to the backup system or old software in minutes. The up to hours interruption to some traffic flow is only due to the time to rebuild the traffic flow to one that works safely; in an airport like Heathrow, as it’s working at >95% capacity, a small blip can’t be recovered in minutes. NATS does its software upgrades only in quiet periods and would never chose a May Bank Holiday w/e to do it. Unlike an airline whose planes are on the ground in incidents like current one, so safe, ATC has many planes in the sky so has to be much more careful.