The leakage of SF6 switchgear has the following characteristics:
Hidden nature: It cannot be directly detected; it requires scientific methods for locating the leakage points.
When the gas leakage pressure decreases, it directly affects the breaking performance of the circuit breaker.
Repeated gas supplementation, coupled with the uncontrolled gas supplementation 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 points are diverse. They are not limited to sealing issues. Factors such as sand holes in the pouring ports, sand holes in weld seams, the size of the sealing grooves, and air leakage from pressure gauges all account for a certain proportion.
The task of replacing the leaking components during a power outage is quite demanding and requires high standards of craftsmanship. In particular, the disassembly process of the combined electrical equipment poses significant additional safety technical risks. There are also issues related to risk decision-making regarding the disassembly of the equipment and the pressure-protected leak sealing during non-power-off operations.
The main areas and causes of air leakage in switch equipment are as follows: Air leakage occurs mainly at pipe joints, flanges, valves, weld seams, and sand holes, etc. These areas are the key points for leak detection. There are also very few cases of leakage in the middle section of the pipeline or tank, which are difficult to detect. The main causes of air leakage include insufficient tightening force of joints and flanges, thermal expansion and contraction, aging of sealing components, scratches or slag on the sealing surface, manufacturing defects, and installation defects.
SF6 gas leak detector
The detection methods for SF6 gas decomposition products in equipment include gas chromatography, mass spectrometry, infrared absorption spectroscopy, detection tube detection method, chemical analysis method and sensor method, etc. Different methods have different detection principles, technical conditions and application scopes. The most commonly used ones are gas chromatography, detection tubes, and electrochemical sensor method. Among them, the electrochemical sensor method is widely applied in the field, providing the application basis for the detection technology of SF6 gas decomposition products. This article focuses on the application technology of the electrochemical sensor method.
Electrochemical sensor technology utilizes the chemical reaction of the measured gas 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 measured gas. Electrochemical sensors have good selectivity and sensitivity and are widely used for on-site detection of SF6 gas decomposition products.
The SF6 decomposition product analyzer based on the electrochemical sensor principle has been widely used for the live detection of SF6 gas in operating equipment. The main technical requirements for the analyzer are as follows:
It can effectively and simultaneously detect the contents of SO2, H2S and CO in the equipment.
The detection range for SO2 and H2S gases is no less than 100 μL/L, and for CO it is no less than 500 μL/L.
The gas flow during the test shall not exceed 300 m³. uL/L
The instrument interface meets the requirements of the equipment and can withstand the internal pressure of the equipment.
The test results are expressed in terms of volume ratio. The obtained results should retain one decimal place of the significant figures. 3.2 During the test, carefully inspect the gas pipeline, the connection between the detection instrument and equipment, and prevent gas leakage. If necessary, the test personnel should wear safety protective equipment.
During the measurement, slowly open the gas path valve, adjust the gas pressure and flow rate. During the measurement process, keep the gas flow stable and constantly monitor the gas pressure of the measured equipment to prevent the equipment pressure from dropping.
Under the condition of reliable safety measures, the detection of SF6 gas decomposition products is carried out while the equipment is energized.
The exhaust gas from the tail end of the detection instrument should be collected and treated.
