There are two different levels of network in the UK: Transmission; and Distribution. While large scale generation tend to be connected to the Transmission network (see previous blog LINK), smaller scale generation is connected to the Distribution network. The Distribution network operates at lower voltages compared to the Transmission network with voltages reduced by Transformers at the point where the two networks meet, from 400kV from Transmission network, to 132kV (or lower) at the Distribution network. The electricity is then transferred to local demand, where again the voltage is reduced to 11kV for towns (for example) and finally 230V for homes where the electricity is safe to use for home appliances.
Who they are
In the UK there are six Distribution Network Operators (DNOs), covering 14 geographical locations: Scottish & Southern Electricity Networks (SSEN); Scottish Power Energy Networks (SPEN); Electricity North West (ENW); Northern Powergrid (NPG); UK Power Networks (UKPN); and Western Power Distribution (WPD). The below map highlights the geographical area each organisation covers (Source Ofgem LINK):
DNOs are not to be confused with electricity suppliers: if you have a power cut, call your local DNO (Google will be able to help you find out who they are if the above map doesn’t help you); if your electricity bill comes in at £10,000, call your electricity supplier.
The distribution network will experience significant levels of change in the coming years as the demands on it increase due to the uptake of Electric Vehicles (charging points will be connected to the distribution network), as well as increasing levels of small scale renewable generation connecting to their networks. Distribution Network Operators are adapting to this by moving towards becoming Distribution System Operators (DSO), where they have a much more active involvement in the way their local network is operated (much in the same way as National Grid Electricity System Operator control and operate the wider Transmission network). They are looking to create local energy markets where they can procure services from locally connected generation to help them maintain and operate their network, with the aim of developing this market for domestic users to participate in.