The 400 kV grid system for England and Wales

The paper describes, in Part 1, a study of probable long-term requirements of the main transmission system in England and Wales. The possibility of continuing to extend at 275 kV is compared with the alternative of introducing a higher voltage, either 400 or 500 kV, and the reasons for deciding to adopt 400 kV as the next step in transmission voltage are given. The research work associated with the development of overhead lines suitable for operating at 400 kV in England and Wales is described in Part 2 of the paper, while Part 3 gives a summary of the main features of the design of the 400 kV substation equipment, overhead lines and cables which will be used to implement the proposals.