Nuisance tripping problem taking too long to solve

The problem of nuisance tripping by embedded generators should have been fixed years ago, the head of the Energy and Climate Intelligence Unit (ECIU) has argued.

Commenting on the findings of several investigations into August’s blackout, ECIU director Richard Black said the issue of overly sensitive loss of mains protections must be addressed as a matter of priority.

“If there’s one thing that would seem to be an absolute no-brainer from this, it’s fixing this problem with embedded generation, that’s been about for ten years,” he remarked.

Black said Germany had also faced a similar problem but “they just fixed it within a few years by basically telling the industry,” adding: “It doesn’t seem that hard.”

He proffered two reasons for the slow progress: “One is that there was a problem about who should be responsible for this: is it the generators themselves, is it the energy network companies or is it National Grid? And clearly that was never resolved.

“But also, the advisory process seems absolutely unwieldy. There was one document that noted this particular advisory committee had already held 37 meetings and they hadn’t actually come to the end of their conclusions on this one small issue.”

The electricity system operator’s (ESO) final report on the incident estimated that around 500MW of embedded generation was tripped by loss of mains protections in the run up to the power cut.

A few days before it happened, Ofgem approved a modification to the Distribution Code requiring existing generators to replace or recalibrate their protection systems.

Both the ESO and Energy Emergencies Executive Committee (E3C), which recently published the interim findings from its investigation into the blackout, have recommended a review of the timetable for changing loss of mains protections.

Black made the comments at a media briefing hosted by the ECIU, which was also attended by Rob Gross, the director of the Centre for Energy Policy and Technology at Imperial College London.

The blackout occurred after the ESO was unable to cover the rapid loss of nearly 2GW of generation triggered by a lightning strike on the transmission network. In the wake of the event, there have been calls for the ESO to increase the amount of frequency response it holds in reserve, which stood at around 1GW at the time.

Gross said this may be a worthwhile “hedge” against the increasing volatility of the power grid, particularly as the ESO will eventually need to procure more frequency response to cover the potential loss of one of the reactors at Hinkley Point C when it comes online.

“You might want to say: Well, the system’s changing. Things that we haven’t thought of could be more likely. Therefore, as precaution instead of holding one gigawatt we’re going to hold two gigawatts.”

He continued: “I’ve been saying for years that the doomsayers are wrong and that having lots of variable renewables doesn’t mean the system is going to be less reliable. We’ve produced lots of evidence for that being the case.

“But we would be moving into uncharted territory. Pragmatically if you could do something that gave you a bit more of a hedge and it didn’t cost very much, then why would you not do that?”

He said although this could cost a fair amount overall, the impact on individual consumers would be limited once spread among millions of households and businesses.