Nuisance tripping project reaches halfway point

Work to prevent distributed generators from nuisance tripping in response to disturbances on the power grid has so far covered 10.4GW of capacity.

National Grid Electricity System Operator (ESO) said it has received 4,776 applications to the accelerated loss of mains change programme (ALoMCP) so far – approximately half of those that need to make the changes by April 2022.

Of those that have applied, 2,336 have made the necessary changes – equating to 4.9GW of capacity.

ESO’s network operability manager Graham Stein told Utility Week that the changes made so far have already led to a reduction in spending on managing loss of mains protection – the annual bill for which sits at between £150 million and £200 million.

ALoMCP, which was launched last September, is seeking to increase the rate of change of frequency (RoCoF) protection distributed generators have in place. RoCoF uses the rate of frequency change to detect the absence of a connection to the system and disconnects the site if that rate exceeds a specific value. The requirement has been changed from 0.125 Hz/s to 1 Hz/s with a definite time delay of 500 milliseconds.

The programme is also seeking to shift those generators which use vector shift as loss of mains protection over to RoCoF.

Stein said the programme has so far had a good success rate with those generators moving away from vector shift.  However, only around 5 per cent of applications to date have been from those using ROCOF generators. ESO had been expecting around 10 per cent.

He said: “That could be a case of us not getting the message out there effectively or perhaps there just aren’t as many out there as we thought.”

To stimulate greater engagement, ESO introduced a fast-track system this summer. This offers an additional payment of £5,000 to sites that meet specific criteria and can commit to making the required changes quickly.

Stein said the collaboration with distribution network operators had been integral to the success of the project.

“Not only are they the ones with the direct relationship with their customers but they have also been the ones verifying that the work has been done.”

He said coronavirus caused some early delays but does not expect it to have major implications over the full term of the programme. Some adjustments have had to be made in terms of virtual site visits and other forms of verification, he added.

He added: “We are very pleased with progress so far and it has already meant that we can reduce expenditure. But we know we have further to go.

“The people who have engaged so far are the people you would expect to – larger organisations who have worked around the sites they have.

“We appreciate there are going to be sites out there that just don’t know this is happening.”

He added that Scotland, Wales and Yorkshire had so far been the most active regions.