High Voltage Circuit BreakerHV AC Switchgear

Gasket design for SF6 leakage

Leaks occur because the gaskets used in the equipment begin to leak as the gasket material deteriorates with age and use.
3 factors are important in gasket design:

  • Hardening of the gaskets. High ambient temperatures and heat produced by the current passing through the circuit breaker in normal use affect the gaskets’ elasticity and harden them.
  •  Chemical attack. After years of use in substations, SF6 gas undergoes chemical changes as a result of arcing due to current interruptions. These short circuit interruptions change the composition of pure SF6 gas and partially decompose it.
  • Corrosion. Filler material used in equipment seals is attacked by the external environment.

Two O-ring seals were located very closed together with a leak checking system between the two.Grease was used to protect against air borne pollutants.
Now we use 3 seals in one seal of a special shape. The main seal is protected from internal and external corrosion by two auxiliary seals. The seal is located in a groove designed to avoid any risk of scratching when the equipment is assembled, but the main seal now has a large surface to limit the risk of leakage if the metal gets caught in the seal assembly.

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