Oil/Paper Insulation HVDC Performance

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 October 2010

01 April 2014

42 months

£344,000

Power

London

Network Innovation Allowance

Project Contact, National Grid Electricity Transmission

The objective of this project is to better understand the DC impacts on transformers. National Grid will evaluate the success of the project by seeing if the results provide useable information which supports the specification and operation of HVDC equipment.

Recent work in CIGRE has highlighted that oil resistivity can greatly influence the stress distribution within an oil-paper insulation system in a DC stress environment especially during voltage changes such as polarity reversals. There have been several failures of bushings at Sellindge (convertor station) during or shortly after polarity reversals and there is evidence that the factory testing of DC transformers is inadequate to cover service conditions. A new CIGRE group is being established to look at this further and this work could usefully link to this group. The measurement of the DC conductivity of oil is not routine and a repeatable method needs to be established. This project will provide the knowledge to specify appropriate tests on new transformers and make sure that oil quality in service is maintained to suitable levels. The method that has been proposed for this project includes; The project will probably employ two PhD students, one looking at oil conductivity measurement and the other looking at space charge measurement, the two projects will allow a full understanding of the charging and dielectric strength of an oil-paper system under DC conditions. ; Literature report on oil conductivity, measurement and effect on stress in insulation Preliminary tests on oil conductivity and charge measurement Results of tests on insulation under different conditions, effect of electrode materials and temperature on DC conductivity Results of investigation into oil DC conductivity measurement and the effect of oil conductivity and pressboard condition on charge retention and migration on surfaces and the potential for creep breakdown on surfaces. Final report in form of PhD thesisNote : Project Documents may be available via the ENA Smarter Networks Portal using the Website link above

17/09/18