How we balance the country’s electricity transmission system

09/08/2013

When we watch television, turn the lights on or charge our smartphone, we rely on electricity that has passed across the very high-voltage transmission network.

We are responsible for managing the flows of electricity to homes and businesses on a real time basis. Once electricity is generated and enters our network, our job is to ‘balance’ the network, ensuring supply and demand are matched second by second.

Balancing the system to make sure that demand is met by supply is one of the most important things we do, and it is becoming more challenging as intermittent generation – such as wind power – becomes a bigger part of the overall energy mix.

Frequently asked questions about how we balance the electricity transmission network

How we do it

Windfarm and transmission pylon

As we continually work to balance the system, we can ask generators of all kinds – not just wind farms – to come on or off the grid to help us balance supply and demand, or to manage ‘constraints’ – effectively bottlenecks – in the network.

This is something we do many times every day, and have done for many years. It is a normal part of our job, and we have a number of well-proven tools to help us do it, including buying generation onto or off the network one or two days ahead of real time, and bids on the balancing mechanism within one or two hours of when the energy is needed.

Our demand forecasting team is always planning ahead, so we can make sure there is enough back-up power available to cover any potential shortfall, whether that’s due to a power station breakdown or an unexpected event.

For instance, in very high winds, many wind farms will shut down their turbines for their own protection, often automatically. When that happens, we can use our backup generation to balance the system.

Sometimes it works the other way too. In early January 2012, we asked some wind farms in Scotland to stop generating for a few days. This was for two reasons.

First, the very high winds were affecting the transmission network, causing constraints. Also, demand in Scotland was low because of the New Year Bank Holidays, so that additional energy wasn’t needed.

Balancing up the costs

There is a cost in this balancing activity, but it is very low for consumers - no more than a few pence a year on a typical electricity bill. As part of a ‘balancing mechanism’, each power station makes a ‘bid’ that reflects what they are willing to be paid – or to pay – to be taken off or moved on to the network.

In 2012/13, the total cost of balancing the network was £803million which makes up around 1 per cent of consumer bills. Ofgem regulates these balancing costs and gives us incentives to keep them down.

The balancing costs are made up of a number of elements and one of these is constraint costs.

The total cost of constraints in 2011/12 was £324million. Of this amount, £31million was for wind constraints.

The total cost of constraints in 2012/13 was £170million. Of this amount, £7million was for wind constraints.

Wind constraints reduced because of the investment made in reinforcing the transmission network. The reinforcements increase the capacity to transport more energy, but while doing the work, we need to take parts of the network out of service which reduces the capacity and leads to us needing to constrain some energy in the interim.

Of course, more generation is connecting to the system so there will continue to be outages to aid the investment of new transmission infrastructure, which means we will still be managing wind constraints but not proportionally to the capacity of installed wind.

Adapting for the future

We expect that new technology, from smart meters to innovative forms of electricity storage, could offer new opportunities for large and small consumers to help us balance the system.

We also carry out a number of consultations to give the rest of the industry an opportunity to contribute to the debate.

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