Development and trials of the 400 kV integral pipe-cooled cable system

The need for reduction in wayleave requirements for cables for undergrounding of CEGB 400 kV very-heavy-duty lines has led to the development of the integral pipe-cooled cable system. The thermal design of the system is described and the various practical problems, pertaining to the installation of larger 400 kV cables in pipes, are outlined. Two field-trial installations have been constructed, the second being designed to resolve problems of cable movement which were not fully solved due to practical limitations in the first trial. The main results of both trials are reported. The applications, limitations and economic advantages of this cable system are briefly discussed.