System Operator seeks new options to manage low demand: negative capacity reserve and accessing distribution assets ‘on the table’

National Grid ESO said that a ‘Negative Capacity Reserve’ was one option on the table to help manage expected prolonged periods of low demand over the summer due to Coronavirus measures. It asked industry members for their suggestions on new products to manage the system during such periods, including negative fast frequency response. It has written today to all power asset owners to ask them to detail their plant capabilities, “Specifically do you have the ability to take megawatts off the system, with what fuel type and in what timescales can you take it off”.

In a regular weekly briefing the system operator added, “Tell us what’s possible. There may be a requirement for additional services we haven’t had to use before”. Its solutions may include “accessing resources” at the distribution network level to raise demand.

The system demand is “manageable but very low for this time of year,” NGESO said; in fact on the morning of Monday (6 April), typically a peak period, demand was 16.8GW – just 1GW above the lowest demand ever. NGESO has experience of operating during short periods of low demand but expects to have to manage over longer periods as we head into the summer.

Controlling the system at times of low demand is more challenging for the system operato,r because there are relatively few power assets in operation and so-called ‘dispatchable’ plant such as gas turbines, which can provide more system support, are not operating. NGESO can ask them to start up, but that increases costs for customers.

In addition, in a low demand period with low ‘inertia’, the system has less ability to ‘ride through’ small disturbances and response is less effective in stabilising it. That is one reason why NGESO said it does not want suspension of a longstanding programme to adjust thousands of small plants, so they do not automatically disconnect too easily. But the programme involves site visits to make the corrections and the programme steering group is said to have decided that the project was not ‘essential work’ during CV-19 measures. NGESO said it was “Very important and we want it to proceed,” and last week said it was working on prioritising the most important sites.

In the weekly briefing the SO said it was also contacting asset owners “to ensure they have a clear understanding of any emergency instructions they may need to meet”. It repeated an earlier request for suppliers and third party intermediaries to provide anonymised data on power use, disaggregated into industry sectors. The SO wants it to benchmark its models and improve its projections on demand.

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