What is thermal constraint management and why is it important?

Our job is to balance the electricity system 24 hours a day, 365 days a year making sure homes and businesses have the power they need whenever it’s needed. We move electricity safely, reliably and efficiently through the equipment of the electricity system –pipes, pylons and substations for example.

There is a physical limit to the amount of power which can be transmitted through any piece of equipment and often that limit is set to ensure that equipment does not become overloaded and overheat. 

If the pattern of electricity generation and demand in a certain area mean that this limit could be exceeded and a piece of equipment possibly overloaded, we take action. This is done through thermal constraint payments - paying generators to vary their output and optimize the flow of electricity.

The cost of these payments is continually weighed up against the cost of building new infrastructure to ensure we keep the costs of running the system as low as possible, and offer the best possible value to consumers. If a thermal constraint continues to be, or is forecast to be expensive, we will consider if reinforcing the network in that area would be the most economical solution. This could mean upgrading the capacity of the existing power lines, adding new lines, or creating separate electricity ‘highways‘  to bypass the affected area, such as the Western HVDC cable being commissioned between South Scotland and North Wales.

To give greater insight on these payments we publish a map each day of costs for thermal constraints across a number of significant constraint boundaries. We also provide a snapshot of the limits and flows at these boundaries for the day ahead too.