Classification of measurement methods for SF6
The measurement methods for the moisture content of SF6 gas are classified into three types based on different principles: electrolysis method, dew point method and capacitance-resistance method.
1) Electrolysis method. This method uses the Coulomb method to measure trace moisture in gases, and its quantitative basis is Faraday’s law of electrolysis. When the measured gas flows through the electrolytic cell at a constant flow rate, the trace moisture in the gas will be completely absorbed by the P2O5 membrane layer and be fully electrolyzed. This method is a measurement method. Its advantages are stability and no drift. However, the disadvantage is that the lifespan of the electrolytic cell is limited, it needs regeneration, and it has a high requirement for gas flow rate.
2) Dew Point Method. The dew point refers to the temperature at which water vapor in the air or other gases reaches saturation and forms frost. The dew point meter is the most accurate, reliable and fundamental measurement method, and is widely used in standard transmission. However, its drawback is that it is relatively expensive and requires experienced personnel to operate and maintain.
3) Resistance-capacitance method. The resistance-capacitance method is used for humidity measurement by taking advantage of the fact that the resistance or capacitance value of the humidity-sensitive element changes in a certain pattern with the variation of gas humidity. Due to the fact that the relationship curve between the sensor’s electrical parameters and gas humidity will change over time and with the use of the instrument, such instruments need to be frequently calibrated to ensure accurate measurement.
Field test method for SF6 moisture analyzer
Connecting SF6 equipment
Connect the threaded end of the measuring pipe to the switch connector, tighten it with a wrench, and close the needle valve at the other end of the measuring pipe; then insert one end of the quick connector on the test pipe into the sampling port of the SF6 moisture tester; connect the exhaust pipe to the outlet. Finally, connect the switch connector to the measurement interface of the SF6 electrical equipment, and tighten it with a wrench.
2. Check the battery level
When using direct current, please check the battery level displayed on the upper right corner. If the battery level is below approximately 20%, please turn off the device, charge it, and then continue using it.
3. Start the measurement
First, fully open the needle valves on the measuring pipeline. Then, adjust the flow rate using the flow valve on the panel, and set the flow rate to approximately 0.5 LM. Start measuring the SF6 dew point.
This measurement process takes 5 to 10 minutes, and each device requires an additional 3 to 5 minutes afterwards.
4. Storing Data
After the equipment measurement is completed, the data can be saved in the instrument. Press the “Confirm” key to display the operation menu. The specific operation method can be found in the following section.
5. Measuring other equipment
After the measurement is completed, close the needle valve on the measurement pipeline and the regulating valve on the dew point meter. Remove the adapter from the SF6 electrical equipment. If it is necessary to measure other equipment, continue the measurement of the next device following the above steps.
6. Measurement completed
After all the equipment measurements are completed, turn off the power supply of the moisture analyzer.
Post time: Mar-17-2026