The leakage of SF6 switchgear has the following characteristics:
It has concealment: it cannot be directly discovered; scientific methods need to be used to find the leakage points.
A decrease in the leakage pressure directly affects the breaking performance of the circuit breaker.
Repeated gas replenishment, coupled with the loss of control over the gas replenishment process, can easily lead to excessive moisture content in the gas and deterioration of the overall performance of the circuit breaker.
The types of leakage are diverse. It is not only due to the problem of sealing parts, but also factors such as sand holes in the pouring port, sand holes in the weld seam, the size of the sealing groove, and air leakage of the pressure gauge account for a certain proportion.
The workload for replacing the leaking components during power outage is considerable and the technical requirements for the process are high. Especially, the additional safety technical risks in the disassembly and treatment of combined electrical apparatus are significant. There are also risk decision-making issues regarding the disassembly and treatment of equipment and the pressure plugging without power outage.
The main locations and causes of gas leakage in switchgear are mainly at pipe joints, flanges, valves, weld porosity and other areas, which are the key points for leak detection. There are also a very small number of cases occurring in the middle sections of pipelines and tanks, which are not easy to be detected. The main causes of gas leakage include insufficient tightening torque of joints and flanges, thermal expansion and contraction, aging of sealing parts, scratches or slag inclusion on sealing surfaces, manufacturing defects and installation defects, etc.
The detection methods for SF6 gas decomposition products in equipment include gas chromatography, mass spectrometry, infrared absorption spectroscopy, detection tube detection, chemical analysis, and sensor methods, etc. The detection principles, technical conditions, and application scopes of different methods vary. Among them, gas chromatography, detection tubes, and electrochemical sensor methods are more commonly used. The electrochemical sensor method is widely applied on-site, providing a technical basis for the application of SF6 gas decomposition product detection technology. This article focuses on the application technology of the electrochemical sensor method.
Detection Principle
Electrochemical sensor technology utilizes the chemical reaction of the gas to be measured under the action of a high-temperature catalyst to change the output electrical signal of the sensor, thereby determining the composition and content of the gas to be measured. Electrochemical sensors have good selectivity and sensitivity and are widely used in on-site detection of SF6 gas decomposition products.
Detection instrument
SF6 decomposition product analyzers based on the principle of electrochemical sensor technology have been widely used for on-line detection of SF6 gas in operating equipment. The main technical requirements for the analyzers are as follows:
It can effectively and simultaneously detect the content of SO2, H2S and CO components in the equipment.
The detection range for SO2 and H2S gases should not be less than 100 μL/L, and for CO, it should not be less than 500 μL/L.
The gas flow rate during the test shall not exceed 300 m³. uL/L
The instrument interface meets the equipment requirements and can withstand the internal pressure of the equipment.
Precautions during the test
The test results should be expressed as a volume ratio and should be retained to one decimal place. During the test, the gas pipeline and the connection between the testing instrument and equipment should be carefully inspected to prevent gas leakage. If necessary, the testing personnel should wear safety protective equipment.
When measuring, slowly open the gas line valve and adjust the gas pressure and flow rate. During the measurement process, keep the gas flow rate stable and constantly monitor the gas pressure of the equipment under test to prevent a decrease in the equipment’s pressure.
Under the premise of reliable safety measures, SF6 gas decomposition product detection can be carried out when the equipment is energized.
The exhaust gas discharged from the tail of the detection instrument should be recycled and treated.
Post time: Feb-07-2026