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London Area 132kv Cable System Replacement

When a distribution network operator (DNO) identified the need to replace two of their 132 kV fluid-filled cable circuits, they engaged UK construction firm Clancy to tackle the issue. Originally installed in 1959, the circuits were leaking oil and at risk of failure due to degradation. Clancy brought us onboard to produce a concept design for the replacement cable system.
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The existing cable route, comprised of two 132 kV circuits, covered a distance of 9.6 kilometres (6 miles). Following consultations with representatives from the local government authority, a new route was agreed which extended the length to 11.2 kilometres (7 miles). This new route had to traverse an industrial zone and several residential areas¡ªand a number of significant installation challenges were present along its length. These included a dual carriageway, a tramline, a railway line, and several rail bridges under which cables needed to be installed.

To overcome these challenges, we developed a concept design for the replacement cable system which included a cable sizing study, earthing and bonding design, and cable thermo-mechanical forces calculations. We proposed ducted burial as the installation method for most of the route, with horizontal drilling recommended to cross beneath the tramline and railway. Specifications for joint bays, cable terminations, and cleating arrangements, were also produced.

Equipped with this information, the DNO and Clancy were able to move forward with replacing the older oil-filled cables with new, environmentally friendly XLPE-insulated cables.