Use of SF6 Gas in the Electrical Transmission Industry

July 20, 2020

By: Leon Best

Sulphur Hexafluoride (SF6) gas circuit-breakers have been a critical technology under review by the European Union (EU) for some time.

Problem

A site required upgrades to its existing High Voltage (HV) electrical switchboards. The site’s aim was to reduce all arc flash hazard categories to ‘everyday work clothing’ or less.

Bluefield identified that the existing switchboard equipment utilised the SF6 gas-type circuit-breakers

SF6 gas circuit-breakers have been a critical technology under review for some time.

Bluefield further investigated the risks of use, possible alternatives, and opportunities for the site to reduce its arc flash hazards.

Investigation

  • The European Union EU regulation 517/2014, due to be reviewed in 2020, will potentially declare the complete phasing out of the use of SF6 gas type equipment.
  • SF6 is the greenhouse gas with the most significant global warming potential (GWP) - 22,800 times more than CO2.
  • SF6 decomposes under electrical stress, forming toxic by-products; this by-product, disulphur decafluoride (S2F10), has a toxicity on a par with phosgene gas, and is extremely hazardous to employees.
  • Only licensed or authorised hazardous waste managers are permitted to handle, transport, and recycle SF6 (OPSGG 1989)
  • A significant number of assets in the site’s HV electrical infrastructure utilised SF6 gas type circuit breakers.

Results

Bluefield recommended the use and future change out to Vacuum-type circuit-breakers. Service experience shows them to be reliable, almost maintenance-free, and safe under operating conditions. They have negligible global warming potential (GWP), with no reporting required under the Synthetic Greenhouse Gas Management Act, no suffocation or poisoning risk due to toxic by-products or leakage, and no fire hazards or explosion risk due to over-pressurisation or overheating of the gas.

Bluefield also recommended the installation of remote or wireless switching of circuit breakers to remove the arc flash hazards associated with this task.

The site subsequently changed its business philosophy on the use of SF6 gas-type circuit-breakers. They implemented the use of Vacuum circuit-breakers, and utilised remote switching to achieve their target for arc flash reduction and risk mitigation.