Coal power stations in the UK were instructed to warm following a request from the French system operator that help might be needed.
France’s RTE said a strike across their generation fleet on Thursday could place their place in an alert status.
Later, the ESO confirmed that the three coal units instructed to warm on Wednesday night were stood down as they were no longer required.
An ESO spokesperson said: “In support of mutual cooperation between Great Britain and its neighbouring electricity networks the ESO answered France’s request for additional GB generation to be able to provide assistance today if required by warming the contingency coal units.
“The ESO was able to take this action to support the French network in avoiding consumer disconnections, as the GB network is currently operating as normal and this action would not have placed GB consumers at risk. Following further assessment of network margins in both countries the ESO has now stood down these coal units.”
In reaction to coal power stations being warmed up for third time this week, Tom Greatrex, Chief Executive of the Nuclear Industry Association, said: “These are increasingly concerning times for the security of our electricity supplies.
“Repeated warnings over tight supply margins, the scale of power imports and emergency measures being taken, demonstrate that you cannot offshore energy security.
“For long-term energy security, we need to urgently get on with a programme of new nuclear capacity to provide secure, reliable, clean power for the future. The failure to do so a generation ago has left us in this increasingly precarious position and repeating past mistakes will leave the UK over-exposed to the variability of some power sources and the volatility of dirty fossil fuel prices.”
A government spokesperson told ELN: “The UK has secure energy supplies, including from our North Sea gas reserves and we are confident in our plans to protect households and businesses, including vulnerable households, in the full range of scenarios this winter.
“In our British Energy Security Strategy we announced that Government will set up Great British Nuclear, a new body to help meet our ambition of up to 24GW of nuclear power by 2050.”