Rating Impact of Non-isothermal Ground Surface (RINGS)

Completed

Other Power and Storage Technologies(Electricity transmission and distribution)

Applied Research and Development

ENGINEERING AND TECHNOLOGY (Electrical and Electronic Engineering)
ENVIRONMENTAL SCIENCES (Earth Systems and Environmental Sciences)

Not Cross-cutting

Project Contact
National Grid Electricity Transmission

Network Innovation Allowance

Ofgem

01 April 2012

01 April 2014

24 months

£110,000

Power

London

Network Innovation Allowance

Project Contact, National Grid Electricity Transmission

The objectives for this project are to; Understand how the ratings of shallow buried cables and cables in surface troughs are affected by non-isothermal boundary temperatures; and Recommendations for temperature conditions to be used in modelling of shallow buried cables and cables in surface troughs. This project will be successful if we understand in greater detail the issues around Cable ratings in non-isothermal ground surfaces.

Recent cable installations have also employed low Thermal Resistivity backfills enabling a higher heat transfer rate from the cable to ground surface, potentially increasing the ground surface temperature. This leads to uncertainty in the actual cable rating available in such situations. It is proposed that monitoring equipment is installed at a site where this situation occurs with the aim of collecting temperature and air flow data over a one year period to cover all seasons and a wide range of loading. The site most suitable for this would be at the Woodhead tunnel where new trough systems have been installed between the sealing ends and the tunnel. This data would then be used by Southampton University to assess how surface temperature is affected leading to a recommendation of temperature range to be used in cable modelling. The IEC 60287 standard describes alogorithms for use with various cable laying conditions including shallow buried cables. The standard assumes ground surface temperatures to be isothermal. The FEAR R&D project undertaken by the University of Southampton confirmed that the use of isothermal surface temperatures was valid for cables, including those in surface troughs, this assumption was shown to be optimistic, leading go possible overrating of such cables. Conversely cables may be underrated to mitigate for the unknown effect of non-isothermal temperatures. Recent cable installations have also employed low Thermal Resistivity backfills enabling a higher heat transfer rate from the cable to ground surface, potentially increasing the ground surface temperature. This leads to uncertainty in the actual cable rating available in such situations. It is proposed that monitoring equipment is installed at a site where this situation occurs with the aim of collecting temperature and air flow data over a one year period to cover all seasons and a wide range of loading. The site most suitable for this would be at the Woodhead tunnel where new trough systems have been installed between the sealing ends and the tunnel. This data would then be used by the university of Southampton, to assess how surface temperature is affected leading to a recommendation of temperature range to be used in cable modelling. he method that has been proposed for this project is: Install temperature and air velocity monitoring equipment Set up remote visualisation of data Analyse data Report on data analysisNote : Project Documents may be available via the ENA Smarter Networks Portal using the Website link above

05/12/18