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Older styles of electricity cables contain oil to improve their insulation properties and to enhance cooling. Occasionally, from time to time, these older cables leak when equipment is damaged, seals deteriorate or as a result of changing ground conditions. When this happens we take steps to ensure that any damage to the environment is minimised and that the leak is fixed as quickly as possible. We’re also putting in place measures to help to reduce the overall number of leaks that we have across our network.

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Oil leakage

WPD Fluid Filled Cable Reported Information

The risks associated with operating fluid filled cable (FFC) and related assets can be reputational, regulatory and financial. The primary risk is associated with leakage of insulation oil to the environment causing environmental pollution, loss of pressure and ultimately cable failure. Leaks typically occur as the cable sheath deteriorates with age; at joint failures or as a result of thirdparty damage. Both the location and repair of leaks can be costly, time-consuming and damaging to the environment.

Since 2014/15 we have achieved the following:

Environment report infographic


FFC oil leakage – all WPD

Environment report infographic

We have seen increases in the volume of oil leaked from fluid filled cable during 2018/19. Fluid filled cable leaks occur more frequently in the autumn and winter months, as a result of changes in ground conditions.

Improving Leak Location

A tagging system has been introduced which uses a small amount of Perfluorocarbon tracer (PFT) chemical. This is incorporated into the fluid and if a leak occurs can be readily detected above ground to pinpoint leaks quickly and to speed up the repair process. This reduces costs, inconvenience to customers and the volume of oil lost to the environment.

During RIIO-ED1 we committed to applying PFT to cables with a history of leakage and internal policy reflects this requirement.

To minimise environmental damage we aim to ensure that:

  • Fluid levels in all our cables are monitored remotely, the loss of pressure triggering an alarm in our Control Centres. This enables us to react quickly to any leak event.
  • Leaks are located quickly preferably using perfluorocarbon tracer (PFT) and repaired.
  • Cables with a history of high leak rates are selected for replacement.