High voltage circuit breakers commonly used for distribution and transmission are reliable if they are able to operate in steady and controlled conditions.
The use of SF6 as quenching gas is extremely important to guarantee a safe operation during the life of equipment.
But if moisture inside the gas exceed critical limits the properties of insulation of SF6 are no more valid and severe damages can happen to switchgear.
Moisture limits are defined by IEC60480 standard which defines the guidelines for checking and treatment of sulfur hexafluoride (SF6) taken from electrical equipment and specification for its re-use.
The inlet of moisture inside tank can bring, during power switching and arc quenching, to chemical decomposition of SF6 into fluorides.
Fluorides indeed do not reduce good insulating properties of SF6 unless the content of humidity is beyond critical limit: at this stage the byproducts also include the high corrosive HF hydrogen fluoride acid.
In addition to above the content of moisture must be kept under control to guarantee that in very cold climates the water vapor can’t condensate creating tracking lines or leakage currents.
PPMV moisture calculation is based on measurement of three physical data: relative humidity HR%, pressure mbar and temperature °K.
Our sensor has two integrated sensing elements able to read at the same time, all the parameters.
