Pressurised Cable Active Control and Monitoring

Completed

Other Power and Storage Technologies(Electricity transmission and distribution)

Applied Research and Development

ENGINEERING AND TECHNOLOGY (Electrical and Electronic Engineering)
ENGINEERING AND TECHNOLOGY (Mechanical, Aeronautical and Manufacturing Engineering)

Not Cross-cutting

Project Contact
Eastern Power Networks plc

Network Innovation Allowance

Ofgem

01 September 2015

01 November 2017

26 months

£1,075,600

Power

London

Network Innovation Allowance

Project Contact, Eastern Power Networks plc

Project Contact, South Eastern Power Networks plc
Project Contact, UK Power Networks

The objective of this project will be to reduce leakage from pressurised cables, by operating oil-filled cables at lower pressure, to such an extent that their operational life can be extended. This will result in fewer pressurised cables requiring replacement and so a lower cost to the customer for the maintenance of the electricity network. This will be done by developing and installing a system using equipment to actively reduce cable pressures to the minimum operating pressure at all times. Specifically there are five objectives within this project: Identify minimum operating conditions for pressurised cables (pressure, load, oil temperature, external temperature)Develop control strategy to identify required control and monitoring points Develop control system to be deployed on selected cable sections Implement control system Active control of cable pressures , leading to a reduction in leakage The success of the project will be judged against the six objectives described above: Identify minimum operating conditions for pressurised cables Develop control strategy to identify required control and monitoring points Develop control system to be deployed on selected cable sections Implement control system Active control of cable pressures , leading to a reduction in leakage Improved Health Index through better management of fluid leakage and thus Health Index improvement on FFCs.

Within UK Power Networks operating licence areas there are 2,409 km of pressurised EHV cables. Within all GB DNOs there are approximately 6,607 km pressurised cables in operation at 132kV, 66kV and 33kV. These cables were installed since the 1920s, with the majority being installed in the 1960s. As these cables age the likelihood of leaks increases. This can be in joints, ancillary equipment or along the cable itself, due to degradation of materials. The current accepted best practise for stopping leaks on poor condition cable is to either carry out a repair on localised area (if practicable) or replace the full length of cable in that section as the whole section becomes unusable and needs to be changed). Often a localised repair is not possible due to the obsolescence of parts, or that the full cable length has degraded and cannot maintain a safe operating pressure. To replace the cable it requires an operator to lay a new cable by open trench method, and then decommission the existing cable. This is a very costly process and makes up a significant part of the network maintenance programme. By reducing the pressure of pressurised circuits, leakage will be reduced, however all current methods of pressure reduction rely on making an assessment of the minimum required pressure based on historic design guidelines which used empirical data from the 1960s. This is because at the time of developing these recalculation methods technology limitations meant only alarm systems were installed. No active control mechanism was installed to manage the cable pressure. The alarms are on/off signals sent via the pilot cable laid with the cable. These are triggered by an analogue dial based in the pit where oil is pumped. As the dial moves, it hits a contact and sends the alarm back through the pilot cable. As fluid lost is a key indicator of asset health of pressurised cables, by actively reducing leakage from pressurised cables the asset life of these assets can be extended and as a consequence a reduction in network maintenance costs to the customer can be realised along with the associated environmental benefits. Therefore an active control mechanism for pressurised cables if proven could offer significant benefits. The project will develop a control strategy and system using technology to enable monitoring and active control of pressurised cable systems. The goal of this will be to enable the pressurised cable to run at a lower pressure, thus reducing leakage along its route. It is anticipated the system will include: Pressure transducers GSM/Mobile communication systems Pressure reduction valves, actuated with remote control Locally based control modules Locally based meter to measure the oil or gas Additional fluid (oil or gas) storage to enable pressure increase or reduction. Using the above technology the system will control the pressure to the minimum operating pressure to ensure leakage is reduced, and that there is less need for site visits to carry out oil or gas pumping. The projects primary focus and trial are on oil-filled cables, however it should be noted that the projects findings are applicable on gas filled cables.Note : Project Documents may be available via the ENA Smarter Networks Portal using the Website link above

26/10/18