hot stuff: real-time thermal rating update

Published: 24th October 2012



Real-time thermal rating takes the temperature to explore the available headroom of the network. Find out more, and watch a CLNR video explaining how weather affects the rating of the electricity network.

hot stuff: real-time thermal rating update

As much as the network revolution is about developing ways to accommodate customer uptake of low carbon technologies, it is also exploring how Northern Powergrid can get the most out of its existing assets. One way is to find out where there is greater ‘headroom’ in the network and use this information to release capacity. Real-time thermal rating (RTTR) is doing just that.

For years, overhead lines and underground cables have been managed according to static ratings, that is, how much current can be pushed through them based on assumed ambient conditions. But weather conditions and topography affect this capacity, especially of overhead lines. Sunny days and wind speeds as well as location - in a valley, on a hilltop, exposed to the wind and so on - all affect the temperature of a line. And the hotter it gets, the less current it can safely carry.

By attaching thermal rating devices at points along a line, it’s possible to get real-time indications of the line’s temperature at any given moment, in relation to the ambient weather conditions and location, which in turn allows the network operator to assess its actual rating under those particular conditions. What they have found is that there can be a significant range, depending on temperature and wind, to safely operate above its assumed rating.

In the future, as demand for electricity grows even more at certain times of the day, and also as more renewable generation devices connect to the network, there will be a greater range of power flow, and also power flows in both directions, placing ever greater strain on the network.

But if the additional headroom capacity can be released when the line’s temperature is lower due to windy or cold weather, it may avoid the need for wholesale network expansion or reinforcement. And obtaining forecasts from local weather stations will add a relatively easy, no-cost element to this innovation.

So how might it work in reality? Imagine a length of overhead line with a town at the end of it, only fed by this line; the load is high but the wind is blowing, which cools the line, allowing the engineers monitoring it to make use of the greater amount of free headroom. However, if the weather warms up, the line may overheat.

Now the network is at risk. But if a thermal rating device can alert the system via an electronic signal that it can’t cater for the increased load, it allows the network operator to relieve the constraint on the network in advance, either by turning on a generator, contacting customers to reduce load or other techniques.

Together with energy storage, voltage control and demand-side response, and with more knowledge about these devices, this may deliver one of the CLNR project’s ultimate goals: cost-effective uplift in network capacity.

To find out more on how weather affects the network in this way, watch our video here.