DEW POINT MEASUREMENT OF SF6 GAS
Sulfur hexafluoride (SF6) gas is an inert insulating gas of high dielectric strength and thermal stability, often used in the power sector for insulating high voltage lines, circuit breakers, transformers and other switchgear equipment.
As SF6 is an inert gas, it can’t cause corrosion but in the presence of moisture, it will cause the formation of highly corrosive acidic by-products, such as Hydrogen Fluoride (HF) and Sulfur dioxide (SO2).
The amount and rate of damage to the SF6 equipment depend on the concentration of this byproduct formed, which is ultimately based on the quantity of water vapour present in the SF6 Gas.
A higher concentration of water vapour presence allows for the formation of a higher concentration of HF & SO2.
A typical dew point range for servicing the SF6 equipment is -50 °C TO -20 °C.
Pure SF6 maybe even drier
The most typical operating pressure within the switchgear is 3 TO 8 bar, but dew point measurement can also be performed at atmospheric pressure
Therefore, the importance of measuring the water vapour content of the gas used within the SF6 filled equipment is to ensure that corrosive electrolytes remain at low concentration level and substantially reduce the risk of damage and cost of maintenance.
The lower the dew point the lower the water content
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