Posted: 28 November 2014
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NISMs – Part of the toolkit
NISMs – Part of the toolkit

Nick Easton, Electricity System Operation, National Grid, on how National Grid ensures that we have an adequate electricity market during the winter months.

The last NISM was issued in February 2012.

"A NISM is a signal to the electricity market that we would like the safety cushion between demand and available supply to be greater."

Nick Easton, Electricity System Operation, National Grid.

In October 2014, the Winter Outlook set the scene for a winter in which electricity margins are expected to be tighter than in recent years. At the same time, at National Grid, we’ve added new services to our toolkit that will help us balance the system in even the toughest winter conditions.

One of the tools we’re most likely to use in our Electricity National Control Centre at National Grid is called a NISM (Notification of Inadequate System Margin). NISMs are a long-standing part of our toolkit. The last time we issued a NISM was in February 2012 – prior to that we hadn’t issued one since 2009.

Issuing a NISM doesn’t mean that we’re moments from a blackout. A NISM is a signal to the electricity market that we would like the safety cushion between demand and available supply to be greater. Typically we’ll issue one up to a day ahead of when the extra power is needed. When we issue a NISM for a future demand peak, generators can respond by making more generation available. They do this by either increasing the available output from generators already expected to be running, or by bringing online additional generators in time for that peak in demand.

We are most likely to issue a NISM for an evening peak in power demand. That’s the half an hour period when families start to get home and cook dinner, but offices and factories are still open for the remainder of the day’s business. However, it’s perfectly plausible for us to issue a NISM during the height of summer, when many generators are on outages for maintenance.

The vast majority of time when a NISM is issued, the market responds, and we are able to withdraw the NISM when we know we’ll have enough generation available. In response to a NISM, large energy users may take a commercial decision to also reduce their demand over the peak in order to avoid higher charges for using the system. This kind of reaction shows the electricity market working as it should.

If the market doesn’t respond by bringing on more generation to help meet demand, or by reducing demand, there are a number of further actions that the control room can take. This includes further signals to the market, using the additional reserves we’ve procured on the supply and demand side, and working with our trading partners to bring in more power through interconnectors.

Ultimately, a NISM is a signal that we can send out to the market so that generators can help us manage the system by making more power available. At this stage it’s difficult to know how many times we’ll issue a NISM this winter, and it may be that we don’t issue any. But NISMs are just one of the tools we can use to help balance the system, and are a tool that our control room has used on many occasions in the past.

  • Pavinder Kaur Babra

    Good morning Nick, I have to ask since we havent issued a NISM in at least the last five/six years has the market been informed re the process and what is expected of them.? We should have informed them around the same time the winter outloook report was published.

  • Rob Wilson

    Please note that the name of a NISM changed to an Electricity Margin Notice (EMN) from 30 Sept 2016 to help clarify that it is simply a signal to the market that National Grid would like the power reserve over the following day to be higher. It also now aligns with the equivalent Gas Margin Notice. The underlying processes remain the same. For more information on this change please follow the link:

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