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Development of Oil-filled Cable Additive

This project aims to reduce or eliminate non-catastrophic cable leaks through the introduction of self-healing fluids (SHFs). These have no impact under normal operation, but at a leak the SHF will crosslink within the defect to form a solid mass that will stop the leak.

Project-on-a-Page summary

Project data

Start date: 01/11/2017
End date: 02/12/2019
Budget: £1.98m

There are over 4,750 km of fluid filled cables (FFCs) within GB DNOs with initial installation dating back as far as the 1930s. These cables are of various design types (e.g. AEI, BICC, Pirelli, Sumitomo, Dainichi-Nippon) and are deployed on distribution network at voltages ranging from 33kV up to and including 400kV. FFCs are insulated by a layer consisting of tightly-lapped cellulosic paper, impregnated with a low-viscosity dielectric fluid that enhances the insulation system electrically and thermally. The cable is typically sheathed in lead to provide armouring and to contain the fluid. Due to the age of the FFC network, the increasing fragility of these sheaths, plumbed cable joints and associated oil circuit is of concern. If the sheath is breached, fluid will leak from the insulation layer.

The project will develop and trial a satisfactory operation of the newly developed self-healing fluid (SHF) in fluid cables that will cure itself during a cable leakage and prevents further loss of fluid.

This is Phase 2 of the project which will cover a wide range of activities, intended to allow the rapid deployment of the technology upon the completion of the project. During the first stage, the project will be concerned with mobilisation and scale up prior to testing within Stages 2 and 3, including the transfer of the SHF formulation to a large-scale oil supplier and the construction and commissioning of primary and secondary rigs. During this phase, UK Power Networks will collect samples of oil from across the network for analysis and cable samples for ageing studies.
The volume-produced SHF will be tested within the primary and secondary rigs to establish the performance of the SHF over a range of conditions expected within operational cables.

This project will demonstrate the satisfactory operation of SHF within live cable circuits and testing of SHF under different environmental conditions which has never been trialled before. The demonstration will develop confidence to adopt the technology into business as usual and reduce leakages from fluid-filled cables.

The project will demonstrate that:

  1. Self-healing cables can be produced in volumes necessary to meet demand from the participating DNOs (and other interested DNOs);
  2. The self-healing cable formulation is compatible with cables under operational conditions and a wide range of temperatures; and
  3. The self-healing cable is capable of significantly reducing or completely eliminating leaks arising from damage to the cable sheath or plumb joints.

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