Application Of Alternative Gases In Retro-Filling SF6 Insulated High Voltage Equipment

Lead Research Organisation: University of Manchester
Department Name: Electrical and Electronic Engineering


Sulphur hexafluoride (SF6) gas has been widely used in high voltage equipment e.g. Gas Insulated Switchgear (GIS) due to its excellent dielectric strength and arc quenching property. However it is one of the six gases included in the Kyoto Protocol, with a high global warming potential. Although SF6 is sealed in the high voltage equipment, utilities including National Grid are often penalised due to its leakage. Environmentally friendly alternative gases to replace SF6 in high voltage equipment have been proposed in recent years. Most of current research focuses on developing new high voltage equipment filled with those alternative gases. The aim of this research project is, however, to investigate the feasibility of retro-filling the existing SF6 equipment owned by National Grid with alternative gases. One of the promising candidates chosen for the project is Fluoronitrile based NOVEC gas. A test system which can replicate typical fields found in 400 kV SF6 filled equipment will be established. The dielectric strength of the alternative gas or gas mixture with SF6 under AC, lightning impulse (LI) and switching impulse (SI) voltages will be characterised, whereas SF6 only will be tested as benchmark. Both conductor to wall bulk gas insulation and spacer surface insulation will be considered. Different percentages of gas mixture under a range of pressures will be studied. Effect of particle contamination and moisture ingression on the performance of the alternative gas/gas mixture will also be studied. Partial discharge measurement and spectrum analysis of gas components after discharge or breakdown will be carried out. A long term withstand test will finally be deployed to verify the long-term performance of the proposed solution.

Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/P510579/1 30/09/2016 29/09/2021
1833101 Studentship EP/P510579/1 29/09/2016 29/09/2020 Loizos Loizou
Description We have discovered that SF6 gas in already existing SF6-designed equipment in the network can be retro-filled (replaced) with a more environmentally friendly gas for insulation applications. Two IEEE journal papers have been accepted for publication to demonstrate the results found.
Exploitation Route This is the beginning in completely replacing SF6 gas in our electrical network which is considered as one of the top six greenhouse gases in the Kyoto Protocol. This will lead in a more environmentally friendly energy transmission network in the future. Lots of other tests such as thermal and material compatibility can be done in the future to assess if the environmentally friendly gas mixtures can be indeed used to replace SF6.
Sectors Energy,Environment

Description SF6 gas is the main dielectric medium for gas insulated equipment in the power industry worldwide. The problem with this gas is that it has a global warming potential of 23,500 times the one of CO2 which categorises it as one of the most potent greenhouse gases in existence. This research work is investigating the feasibility of replacing SF6 gas in our network with a more environmentally friendly gas known as Novec 4710. Initial results are very positive and success of the findings of this project might enable us to replace SF6 in our electicity network and therefore contributing for a reduced greenhouse effect impact from the power industry.
First Year Of Impact 2018
Sector Energy,Environment
Impact Types Societal