SF6 Gas Technology

> What is SF6 gas?

Sulphur hexafluoride (SF6)-gas is an important medium in the electrical industry as a quenching and insulating gas for enclosed medium and high voltage switchgear. It is inert, stable, its good dielectric properties made it suitable for electrical application.

> Why we need to reuse SF6 gas? How to reuse the gas?

SF6 gas is a green house gas and its equivalent damage on environment is about 20,000 times of CO2. Hence as much as there is no immediate replacement for its use in electrical application, SF6 gas emission should be avoided at all times and SF6 should be re-used as much as possibly achievable. Following methods are widely used:

  1. Use of appropriate couplings. Couplings should be metal – metal seal principle in the form of tongue and groove coupling which is vacuum and pressure tight, self opening when connected and self closing when disconnected. For example, DILO couplings are rated for >50bars and vacuum tight. Technology used can be open/close without losing tightness over repeated usage.
  2. Appropriate SF6 gas handling equipment. Often neglected, proper charging device with suitable couplings ensure no leakage, no emission, no contamination.
  3. Recovery of SF gas: SF6 gas can be recovered from a gas compartment, the gas is automatically led through filters which cleans, dry and purify the gas. The gas can be stored in an installed tank in liquid form and then reused back again after checking its properties.
  4. Attend to SF6 gas leakage and repair the leak immediately. SF6 gas leak detectors or SF6 gas warning device are able to monitor SF6 concentration in air and detect leakage.

> Why it is important to ensure the gas quality in the GIS compartment?

Failure to control the SF6 gas quality will result in probable gas contamination. Probable gas contamination if not eliminated in time will cause failure or fatal breakdown of switchgear. A permanent control of the SF6-gas quality in switchgear would basically be advantageous. Thus you receive information on the SF6-gas condition as well as on the functional reliability of the switchgear. SF6 measuring devices are able to tell you the SF6-gas condition in Purity, Dew Point and SO2 contamination levels so you are able to take the necessary action in time.