Tests of Transmission Line Towers

Before the inception of the British Grid System for electricity supply, the overhead electric transmission lines then existing were nearly all of low and medium voltage. The 132 kV. Primary Lines of the British Grid therefore set a new standard in this country, not only of the voltage of the lines and the power they were to transmit, but also as regards the size of conductors, tower heights, spans between towers, and degree of reliability demanded. These factors had their influence on the design of the towers, as the loads to be sustained, both under normal and abnormal (broken conductor)
conditions, were much greater than was usual in this country previously.

H.W.B. Gardiner and W.H. Gomm