Draft PPS 18: Renewable Energy
Annex 1 Wind Energy: Connection to the Electricity Grid
A25. A wind farm is likely to be connected to the electricity distribution network just like any other power station. Small transformers are required to change the generating voltage (likely to be 690V) to a common site voltage which is likely to be 11kV, 33kV or 110 kV. These transformers can either be housed outside or within the turbine tower. The output from the turbines in a wind farm is normally connected to a single point via underground cables.
A26. Responsibility for the routing of electrical cabling onwards from the sub-station to the nearest suitable point of the local electricity distribution network is the responsibility of the District Network Operator, presently NIE. This will be achieved either by a standard 3-wire system mounted on wooden poles or by lines laid underground. It should be noted, however, that laying high voltage cables underground is much more expensive (around 6-20 times greater) than pole-mounted overhead systems and would be likely to be used only for limited lengths and/or in special circumstances. Whilst the routing of such lines by NIE is usually dealt with separate to the planning application for the wind farm, developers will generally be expected to provide details of likely routes and the method of connection (overground or underground).