Anyone who has ever used sulphur hexafluoride gas knows that it is very important to control humidity, and that high humidity will cause corrosion damage to sulphur hexafluoride equipment and reduce its effectiveness. So why are there specific requirements for ambient humidity when filling SF6 gas? What should I be aware of when filling?

Humidity is a prerequisite for SF6 equipment to produce toxic substances. If the SF6 gas contains more than the specified moisture, when its humidity changes, it may condense on the solid insulation surface to make the surface tidal, then the surface discharge voltage of the equipment will be significantly reduced. SF6 gas is decomposed under the action of arc and corona to produce low-fluorine compound gas, if there is no water molecule, this external condition will not produce SO2, HF and other harmful substances, so as to avoid the corrosion of equipment produced by them. Therefore, when SF6 equipment is filled with gas, strict measures must be taken to prevent water from entering.

(1) Before starting the work, the relative humidity of the ambient air around the site should first be measured ≤ 80% (i.e. the density of water vapour in the air and the ratio of the saturated water vapour density at the same temperature), which is the specific number of limiting air water content. If the test is not qualified, measures should be taken or the filling should be repeated in dry and sunny weather.

(2) In order to replace the SF6 leakage gas in time, the main point should open the fan during filling, and carefully observe the provisions that the SF6 content of the air should not exceed 1000ppm. The test should be carried out within a certain time after the start of the work, and the specific situation should be carried out in the middle of the test. If the SF6 gas content increases or exceeds the standard, the component should be inspected in detail immediately to find and eliminate the cause.