Projects

Projects: Projects for Investigator

Sulphur hexafluoride gas (SF6) is estimated to contribute about 0. 2% of the global warming potential of the annual greenhouse gas emissions in the UK. SF6 is also the dominant insulation and interruption material in high voltage equipment with around 10,000 tonnes of it being used by electricity companies in the UK with an estimate emission rate of 15. 6 tonnes (approximately 389,329 tonnes of CO2 equivalent). The possibility of reducing the amount of SF6 in the electricity network and hence the potential impact of the industry on global warming is therefore of great interest. Unfortunately, due to its unique capabilities SF6 has, until now, been very difficult to manage and substitute. Due to its molecular structure, SF6 has a relatively high dielectric strength of nearly three times more than air at atmospheric pressure. However, this same characteristic provides it with an average life of about 3,200 years. This long life-time, added to its strong infrared absorption capability are the reasons for its extremely high global warming potential, which for a 100-year horizon is estimated to be approximately 23,900 times greater than CO2. There are hence several challenges addressing utilities looking at reduce their environmental impact in this area.

National Grid has an ongoing NIA project (NIA_NGET0163) that comprises of the following work packages: Leak Detection and Refilling Leak Sealing and Repair SF6 Capture and ReuseSF6 Alternatives of g3 and CF3I Scottish Power Transmission have also registered an NIA project (NIA_SPT1604) which is looking in detail at the handling and gas management implications for g3. The proprietary gas g3 is effective as a dielectric insulting gas only at higher pressures than SF6. It is therefore not possible to replace SF6 in existing transmission equipment with g3 . This project will undertake research into the potential for the active component of g3 (NOVEC ) to be effective in combination with other gases at various concentrations and pressures to establish whether a replacement for SF6 for use in existing transmission equipment can be found. National Grid has an interest in SF6 free switchgear to improve the sustainability of the network. The aim of this project is to test the dielectric performance of a NOVEC environmentally friendly gas at the 400 kV BIL (Basic insulation level). This project will help assessing the feasibility of replacing SF6 in the existing switchgear with the NOVEC alternative gas. The project will be delivered by University of Manchester with necessary supports from National Grid (e.g. providing bushing) and 3M (e.g. providing NOVEC gas and gas handling solution).

The initial 12-month programme will focus on experimentally verifying the withstand ability of the alternative gas/gas mix under AC, lightning impulse (LI) and switching impulse (SI) voltages. A test system which can replicate typical fields found in 400 kV SF6 filled equipmentwill be established. FEA modelling will be carried out to confirm the test cell design. SF6 will be tested first as reference. NOVEC gas / gas mix will then be tested at an appropriate range of pressures. Both conductor to wall bulk gas insulation and spacer surface insulation will be tested. This project will also include a thermal performance test by supplying a large current to the conductor. This programme will be delivered by a PDRA.

The second phase of work will see an EPSRC Industrial CASE funded PhD student commence work to develop the opportunities to further trial retrofit NOVEC filled switchgear both within the University and at the Deeside site. They will identify the essential testing that would be required to use the equipment on the network and develop test plans that support the delivery of this.

Note : Project Documents may be available via the ENA Smarter Networks Portal using the Website link above