Moisture measurement in SF6-insulated switchgear is essential. That?s why WIKA has improved the performance of the GDHT-20 sensor for this industry. The transmitter, which also provides values for gas density, pressure and temperature, now measures the dew/frost point having an accuracy of �2 K.
Moisture, along with density, is the crucial parameter for assessing the condition of the SF6 gas used. The GDHT-20 continuously monitors its content in the gas. The information from the web monitoring forms the input for a downstream trend analysis. The more precise both density and the moisture measurement are, the more precise this analysis will undoubtedly be.
Predictive maintenance instead of regular maintenance intervals
The model GDHT-20 sensor can be an all-in-one instrument for the web monitoring of SF6-insulated switchgear. It works together with three temperature sensors (red), a pressure sensor (blue) and a humidity sensor (yellow).
The analysis shows the operator when the SF6 will reach a crucial state and when remedial measures should be taken. Because of this, maintenance work or gas treatment is undertaken when action is in fact needed. Predictive maintenance thus replaces the sequence of regular maintenance intervals that was previously necessary to avoid ecological and safety risks.
Too much moisture in the gas compartment is one of these risks. In older plants, moisture mainly increases due to permeation through sealing materials. In younger plant, normally, this is a consequence of moisture remaining on metal surfaces or in insulation materials during tank assembly, due to incomplete evacuation before initial filling with SF6.
Innocent leads to corrosive reaction products that can damage internal components and shorten the service life. If such substances escape, there’s an additional danger to people?s health.
Sly of SF6 moisture is therefore indispensable. Normally, the dew or frost point is used as a parameter. This is the temperature of which the air humidity begins to condense. In the case of SF6, the atmospheric dew point specified by IEC 60376 is -36 �C.
The accuracy of the GDHT-20 of �2 K for moisture measurement is validated at the frost point with an internationally valid reference standard. However, the measuring instrument can also be configured for other parameters (dew point, ppmv, ppmw and relative humidity). The brand new version of the sensor also features greater application flexibility. The GDHT-20 is currently also ideal for density monitoring of the choice insulating gases N2, CF4, O2, CO2 and 3MTM NovecTM 4710.
Note
Further information on the GDHT-20 sensor can be found on the WIKA website. In case you have any questions, your contact will gladly help you.
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You can also find out more about WIKA?s SF6 expertise in the next video: