27.The general location of a substation is initially determined by transmission requirements and line routeing. The substation may be required to increase the supply of electricity from a power station into the national grid system for transmission; or near an urban area, it may be required as a grid supply point to reduce the voltage to lower levels for the local distribution companies. Its general location is defined by these factors. With regard to the precise location of a substation, National Grid has guidelines to assist in siting and designing substations to mitigate their environmental effects. The substation guidelines complement National Grid’s line routeing guidelines and, where appropriate, are used in conjunction with them.

28. Proposals for new or significant extensions to substations, do not require environmental impact assessment under Government regulations or advice. However, National Grid normally undertakes relevant environmental investigations on such proposals, and would report on these investigations in submitting any planning application to the local planning authority.