Flexible rating options for DC operation

Completed

Other Power and Storage Technologies(Electricity transmission and distribution)

Applied Research and Development

ENGINEERING AND TECHNOLOGY (Electrical and Electronic Engineering)

Not Cross-cutting

Project Contact
National Grid Electricity Transmission

Network Innovation Allowance

Ofgem

01 January 2012

01 April 2015

39 months

£245,000

Power

London

Network Innovation Allowance

Project Contact, National Grid Electricity Transmission

To develop tools for the rating and technical assessment of high power HVDC cable options. The work will initially concentrate on cables with mass impregnated insulation. To provide National Grid with techniques to evaluate continuous, transient and dynamic (real time) ratings for DC cable circuits and to evaluate the options and limits for features such as current dependent voltage control. Development of a tool for rating and technical assessment of high power HVDC cable options.

The calculation of current ratings for DC cable is significantly more complex than that for AC cable. The rating is often determined by electric stress constraints rather than considerations of thermal ageing. Ratings are also strongly influenced by thermally induced pressure transients within the cable. In some cases the rating of the cable can be restricted by the cable being too cold. As the normal operating voltage of the cable increases the cable can experience high levels of electric stress while the cable is hot. As the cable cools it is susceptible to electrical failure. Some manufacturers require the converter station to reduce its operating voltage if the current on the link is reduced. The implementation of these current dependent voltage control systems may help protect the cable, but this approach does not align well with the concise cable rating sheet used as part of the CUP package. This introduces an additional level of complexity for Network Operations. The method that has been proposed for this project includes: Initial review of the modelling techniques and materials parameters applicable to HVDC cable ratings Interim report on algorithm development for thermal rating of MI cables Interim report on algorithm development for steady state modelling of electric in non-linear insulating materials Report on temperature and electric field modelling for rating MI cablesNote : Project Documents may be available via the ENA Smarter Networks Portal using the Website link above

14/08/18