During the installation and operation of sulfur hexafluoride circuit breakers, due to reasons such as installation environment and operation methods, they may have various hidden safety hazards with different properties. In order to ensure the arc extinguishing effect of SF6 circuit breakers in power grid operation, improve the safety and reliability of power grid operation, an analysis was conducted on the defects and faults of SF6 circuit breakers in substation operation.
1. Failure analysis of sulfur hexafluoride circuit breaker:
① Sulfur hexafluoride gas contains moisture
Sulfur hexafluoride circuit breakers mainly use sulfur hexafluoride gas as the extinguishing and insulation medium. But it only has high insulation performance and good arc extinguishing ability in relatively pure sulfur hexafluoride gas. If the gas contains water, it usually leads to a decrease in electrical strength, and the chemical reaction between water and arc products can produce sulfuric acid, hydrofluoric acid, or other toxic chemicals, which can be life-threatening. In addition, these toxic and harmful substances can cause serious corrosion to the metal and insulation materials in the circuit breaker, leading to serious insulation damage and potentially leading to equipment explosion.
② Solid impurities can affect circuit breakers
Under normal circumstances, there will be a small amount of free conductive impurities in the arc extinguishing chamber of sulfur hexafluoride circuit breakers. Sulfur hexafluoride gas containing impurities usually reduces the breakdown voltage of pure sulfur hexafluoride gas, leading to arc extinguishing failure.
③ Leakage of sulfur hexafluoride gas
The leakage of sulfur hexafluoride gas is also an important factor affecting the safe operation of circuit breakers. Identifying the causes of sulfur hexafluoride gas leakage, developing corresponding measures, and reducing sulfur hexafluoride gas leakage is an important topic.
2. Preventive measures for sulfur hexafluoride circuit breaker faults:
① Strengthen the control of moisture in sulfur hexafluoride gas. Before filling with new gas, acceptance should be carried out according to the corresponding quality standards, and the purity of the new gas should be greater than 99.8%. In addition, technical indicators such as humidity, air, and mineral oil must meet the requirements of national standards.
② It should be avoided as much as possible to bring moisture due to improper operation or limitations of the inflation device. Before charging, check the pressure of the new gas cylinder to see if it meets the factory's requirements. Then, rinse all pipes and use a hair dryer to heat and dehumidify the joints. When inflating, unscrew the control valve of the gas cylinder, flush the connecting pipe with sulfur hexafluoride gas, and then connect it to an open circuit. The circuit breaker is connected to prevent moisture from entering the circuit breaker. After inflation, the air pressure in the air chamber of the sulfur hexafluoride circuit breaker should be as high as possible above the actual required value. Finally, check the porcelain sleeve and coil of the sulfur hexafluoride circuit breaker to ensure that the porcelain sleeve is intact and the coil is well sealed to prevent moisture or damage to the circuit breaker during installation.
③ Control solid impurities. When selecting sulfur hexafluoride circuit breakers, manufacturers with a complete quality assurance system and qualified product quality should be selected for installation and use units to ensure that the impurity content in the circuit breaker meets relevant standards.
④ During installation and use, it is necessary to regularly check the alarm circuit of the SF6 circuit breaker, strengthen the inspection of the leakage position of the circuit breaker, and regularly check the leakage of the SF6 circuit breaker.
Inspectors should regularly check the latest gas filling records. If the gas density decreases at a rate exceeding 0.01 Ma/year, a leak detector must be used to detect it, and seals and other damaged components must be replaced. If the leakage is very fast, it can expand to the rated pressure, check the pressure gauge, and use a leak detector to find the leakage point of the pipeline joint.
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