Sulfur hexafluoride gas is colorless, odorless, non-flammable, non-reactive, relatively non-toxic, and only asphyxiating in its liquefied form. It is an essential medium for the normal operation of many types of circuit breakers. Therefore, it is necessary to master the methods of replenishing sulfur hexafluoride in switches and filling circuit breakers with sulfur hexafluoride gas. Based on experience, sulfur hexafluoride switch replenishment should be performed under clear weather and good ventilation conditions, following these steps:

  The first step in sulfur hexafluoride switch replenishment is to take the sulfur hexafluoride circuit breaker out of operation and ensure safety measures are in place. Place the sulfur hexafluoride cylinder upright, connect it to an oxygen pressure reducing valve, and attach the filling hose to the reducing valve. Open the cylinder valve, then open the reducing valve to set the low-pressure side to 20,000~40,000 Pa. Use an 8mm diameter copper rod to open the hose valve core and vent for 5~10 seconds to flush the pipeline.

  The second step in sulfur hexafluoride switch replenishment is to measure the ambient temperature around the circuit breaker. Based on the temperature-pressure curve provided by the manufacturer, determine the rated pressure value for the circuit breaker during filling. Unscrew the plug under the C-phase transmission box of the circuit breaker, connect the filling hose, and then slowly open the reducing valve to fill the circuit breaker. When you hear the sound of gas filling in the connecting pipe, it indicates that the reducing valve is working properly. When the gas pressure inside the circuit breaker approaches the rated pressure, fill slowly to avoid excessive pressure in the circuit breaker.

  When the gas inside the circuit breaker reaches the rated pressure, close the reducing valve. First, disconnect the filling hose from the circuit breaker interface and immediately screw the plug onto the interface. Unscrew the connection between the joint and the filling hose. Close the cylinder valve, remove the reducing valve, and store the reducing valve and joint in a dry place for future use.

  The third step in sulfur hexafluoride switch replenishment is to perform a qualitative leak test on all sealing surfaces after the circuit breaker is filled to the rated pressure. If any leaks are found, contact the manufacturer for handling. Additionally, check the moisture content of the sulfur hexafluoride gas inside the circuit breaker. Moisture measurement should be conducted 24 hours after filling. Use the circuit breaker filling port to connect a conical needle-type reducing valve to control the gas flow and measure with a trace moisture detector. The measured data should be compared with the moisture content-temperature curve provided by the manufacturer based on the ambient temperature. During on-site handover, the value should not exceed 150 µL/L (20°C), and during operation, it should not exceed 300 µL/L (20°C).

  The fourth step in sulfur hexafluoride switch replenishment is to record the day's temperature, humidity, and sulfur hexafluoride pressure values. Mark the sulfur hexafluoride pressure gauge indicator for future observation and comparison to determine if there are any abnormalities in its operating state.