National Grid Group chief executive John Pettigrew has insisted Friday’s power cut had nothing to do with renewable energy.
Responding to concerns that increased reliance on renewable energy is reducing inertia on the power grid, he said this was categorically not a factor in last week’s outage, which he blamed on the sheer volume of generation loss.
Speaking on BBC Radio 4’s Today programme Pettigrew admitted that there had been three occasions over the past three months where frequency had fallen to 49.5HZ- the lowest level at which the grid operates. He said this had resulted from generators in England, Scotland and one interconnector separately falling off the network. However, he stressed that in each case the frequency had bounced back to optimal level of 50Hz within a minute and that there had never been any risk to the public.
He said that he expected National Grid Electricity System Operator (ESO)’s interim report to Ofgem – which is due on Friday – would be made public next week.
He also welcomed the department for Business, Energy & Industrial Strategy (BEIS)’s investigation into Friday’s incident – which occurred when two generators, Little Barford combined-cycle gas turbine plant in Bedfordshire and Orsted’s Hornsea Two offshore windfarm, went offline almost simultaneously. He said it was important that the report looked into the reaction of not only National Grid ESO but also the wider infrastructure, including the slow response of the transport network.
In the Today interview, Pettigrew said: “At this stage it looks like the transmission network operated as it was designed. Frequency was back within seven minutes.
“What happened on Friday was that because the loss was so low large – over 1,400MW – frequency dropped to 48.8HZ. As a result of that, all primary response was used and therefore we had to go into our secondary tool, one of which is to disconnect around 5 per cent of the demand. That is done automatically on the system to protect the other 95 per cent of users.”
Pettigrew described media reports about three previous “near misses” in the last three months as “scaremongering”, adding: “If a generator trips off our system, that’s about 1,000MW then you would expect the frequency to fall to around about 49.5hz. In the three incidents that are being quoted this week, it was a generator of around 1,000MW – one in England, one in Scotland and one of the interconnectors. The frequency fell to 49.5HZ and bounced back within a minute to 50HZ. That’s exactly how the network operates every single day so there was no risk to the general public as was inferred in some of the articles.”
Responding to criticism that this way of working is not fit for purpose he pointed to the £10 billion of investment by National Grid over the past decade to increase resilience, which he said is now 60 per cent improved on the position in 1990.
On the impact of renewable energy, he said: “The events of Friday – with two large generators falling off the network simultaneously – a very rare and unique event – were not related to renewables, or at least there’s no evidence at the moment to suggest it was.”
He also pointed to investments in demand side response, battery storage and Dinorwig Power Station as ways in which the industry was tackling the challenge of drops in frequency.