How Statkraft’s team at Rheidol turned the lights back on in Wales

I was a bit startled by the noise on the evening of Friday 6 December, when the emergency alert came through to my mobile phone at home. It was a very rare red warning, issued by the Met Office to nearly 3 million people, alerting that meteorologists expect dangerous, even potentially life-threatening weather imminently.

My team and I had a feeling that this could mean a busy night at our sites in Wales, but there was no way of telling how bad Storm Darragh would affect power supplies. In the early hours of the morning, as most people were asleep, power infrastructure began to feel the impact of winds that were reaching up to 96mph.

Just after 3:00am, damage caused by the bad weather meant large parts of the grid in Wales tripped, knocking one of the generators at our Rheidol Hydropower Scheme off due to the protection settings in place. Dangerously high winds meant that all ten turbines at Alltwalis Wind Farm in Camarthen had to be temporarily halted. 

The team at our Rheidol Control Centre, which monitors all of Statkraft’s UK and Ireland projects, contacted the on-call engineers to alert them, but instructed them not to mobilise, as the ongoing storm made it too dangerous to work.

At 6:49am on Saturday, the massive infrastructure damage meant that the grid was completely lost, and tens of thousands of homes in Wales were left without power.

By then, the weather had calmed down enough to make it safe to work, and the teams started to journey to sites to find out what we needed to do to get the power flowing again. But it wasn’t an easy task. The damage caused by the weather meant detours down rural backroads, with chainsaws deployed to remove fallen trees, and a favour called in from a local farmer to help clear the road.

With mobile phone signals affected by the weather, we relied on satellite phones to communicate, which we always carry as a backup. As it became clear that there was massive damage to the regional electricity grid, the only way to generate power for Mid and North Wales was to get Rheidol back online, in co-ordination with NESO - the National Energy System Operator - and SP Manweb, who maintain the transmission network.

Because in that moment Rheidol was the only functioning power generator in the region, it came with challenges such as manual setting of the generator parameters to ensure that voltage levels, reactive power, and currents on our generators and grid were where they should be. The massive water inflow also caused additional work on filters and pumps to keep the site running.

By around 9:30am, the team managed to re-establish the first section of the grid, with power returning to the whole of Aberystwyth by noon. Rheidol remained the only power generator in the region until late on Monday morning – almost 48 hours later.

Events like this show the hard work carried out by Statkraft’s operations and maintenance team behind the scenes, springing into action and dealing with unexpected events caused by extreme weather, which we may find become more common in the future.

Future projects being developed and operated by Statkraft will eventually see the Rheidol Control Centre directing up to 45% of Great Britain’s entire grid stability services. But it’s a sign of the robustness of our Rheidol Hydropower Scheme, which we’ve been celebrating during 2024, sixty years after it was officially opened, that it continues to play such a vital role in keeping the lights on for people in Wales.