Recent progress in the design of the high-voltage overhead lines of the British grid system

The paper reviews the progress that has taken place in the last 15 years in the design of the steel-tower high-voltage transmission lines of the Central Electricity Board. Lines operating at 132 kV are dealt with separately from those operating at 66 kV and 33 kV. Changes in conductors, joints, insulators and towers have been made in the light of experience, and a record of these is given as well as of other improvements of a minor character. The behaviour of s.c.a. conductor and the methods employed for jointing it are described in detail, and alternative copper conductors are also mentioned. The development of new types of insulators to suit operating conditions in the country is described. The steps taken to reduce the effect of lightning, e.g. more effective earthing, gap control, and the limited use of double earth-wires, are covered, and alterations in towers which have proved advisable are detailed.