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Reference

UK Electricity Supply System

The UK electricity supply system is a free market overseen by Ofgem, the government regulator. It consists of five main parts:

  1. Generators
  2. The National Grid
  3. Distribution companies
  4. Supply companies (not shown)
  5. Consumers

Where's number 4? Supply companies don't own wires or generators, they buy and sell electricity. From a supply point of view, the system works from 1 to 5, but wind often skips step number 2, and connects to the system locally. This is know as embedded generation. The others: coal, gas and nuclear connect the power they generate to the national electricity system , large pylons carrying voltages of 275 or 400 kV. This is good for carrying electricity long distances, but is not something you want to connect to a kettle or a house! Once the large distances are covered, the national grid hands over the power to distribution companies, which own and operate the local distribution system at grid supply points. The power is transformed to progressively lower voltages ( 132, 33 and 11 kV) until the last local stage, where it is transformed down to 240V for domestic use.

From a financial point of view it is a little less direct. Generators sell their power via a trading system called NETA. They fix a price with supply companies, which act as electricity wholesalers. These companies then sell this power to consumers. In order to get permission to use the National Grid and the distribution system they have to pay a use of system charge, based partly on how much power they are moving and the distance between the generator they are buying power off and the consumers they are supplying.

Embedded Generation

Around 2% of electricity is lost during transmission on the national grid. Embedded generators avoid this by connecting locally. They also save money for supply companies which would other wise have to pay use of system charges to the National Grid. Further power is lost at a local level in the distribution system, which can also be reduced with the use of local generator connection.

Embedded generators connect at the same voltage as the distribution system, saving power losses that occur converting between 400 kV and 33 kV which other generators have to do in order to use the national grid. Reducing the demand on the transmission system also reduce the amount of resources needed to maintain and produce transmission equipment, creating additional indirect benefits to the environment.

Local generation can also helps reduce the risk of power cuts in remote areas, if there is a partial failure on the high voltage network the distribution has a source of energy to fall back on. Find out more information about embedded generation at www.distributed-generation.gov.uk

Electricity supply companies are now obliged to get a proportion of their energy from clean, renewables sources. This is good news for wind energy! Follow this link to find out about the Renewables Obligation.

Follow this link for more information about connecting wind turbines to the grid and this one for what wind's intermittency means for the grid.

For detailed information about distributed generation see the energy networks association - www.energynetworks.org.