Condition monitoring and fault diagnosis of the ho

2022-08-17
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Condition monitoring and fault diagnosis of SF6 circuit breaker

SF6 circuit breaker has been widely used in railway electric traction power supply system because of its strong arc extinguishing ability, high dielectric strength, long maintenance cycle and other advantages. SF6 circuit breaker is a high-voltage circuit breaker using SF6 gas as insulation medium and arc extinguishing medium. SF6 gas is a colorless, odorless, non combustible, non-toxic inert gas with stable chemical properties. In corona and arc discharge, SF6 is decomposed into sulfur and fluorine atoms. After the arc disappears, SF6 can be synthesized again. However, near the electrode, due to the metal vapor participating in the reaction, the metal is formed to celebrate the official launch of fluoride and low fluoride in its composite resin research and development and technical service center. When the gas contains water, hydrofluoric acid (HF) with great corrosiveness can be generated. And the anti-interference ability is poor. Hydrofluoric acid is very corrosive to insulating materials and metal materials, so insulating materials containing silicon cannot be used. Therefore, the moisture content of SF6 gas in the circuit breaker should be strictly controlled, and necessary measurement and condition monitoring should be carried out to timely find possible abnormalities and fault precursors and carry out maintenance, so as to ensure the normal operation of the equipment and the reliable power supply of the network

therefore, moisture is the most harmful impurity in SF6 gas. The high water content of SF6 gas will endanger the safe operation of power equipment, mainly manifested in:

• the existence of water "the B-pillar used as the window guide is made of these materials, which affects the formation of gas decomposition products

• when water and acidic impurities are together, the material will corrode, resulting in mechanical operation failure

• moisture will condense on the surface of solid insulation at low temperature, which will sharply reduce the flashover voltage along the surface, leading to accidents

1 fault and maintenance of SF6 circuit breaker

1.1 fault distribution of SF6 circuit breaker

mechanical fault factors of SF6 circuit breaker account for 70%, auxiliary and control circuits account for 19%, and electrical factor faults of main circuits account for 11%

it accounts for 48% of the main faults in the operation that is not closed or disconnected

therefore, the main faults of the accuracy

circuit breaker can be considered as:

• operation faults, including drive and operation faults

• insulation failure, including main contact

1.2 maintenance strategy

in order to pursue better maintenance methods and solutions, condition based maintenance is proposed. Condition based maintenance is a way to judge the abnormality of equipment, predict the failure of equipment and carry out maintenance before the failure according to the equipment status information provided by advanced condition monitoring and diagnosis technology, that is, to arrange maintenance plan and implement equipment maintenance according to the health status of equipment

but for SF6 high voltage circuit breaker, it is still difficult to really achieve condition based maintenance. Only part of the faults of high-voltage circuit breakers have a gradual process, and many faults are sudden. At least at present, it is impossible to predict the possible faults in advance, such as the failure of mechanical load-bearing parts. Even for the aging process of some gradual components, the specific time process has not been revealed. Therefore, it is not realistic to fully implement condition based maintenance at present. However, the process of exploration and efforts towards this goal is accelerating in both manufacturing and operating units

at present, the industry has not formulated a more reasonable maintenance cycle and maintenance items, and the corresponding maintenance and overhaul experience is relatively scarce. According to the actual condition of SF6 circuit breaker, the recommended strategies are as follows

"adhere to daily monitoring, do regular pre-test, and based on condition based maintenance". Based on the means of regular off-line test and monitoring, implement the method of condition based maintenance, and timely arrange the maintenance of exposed and discovered faults and their latent defects. This condition based maintenance includes predictive maintenance and hindsight maintenance

condition detection should be based on two methods: offline test and monitoring, adhere to regular test inspection, develop monitoring means, and safely extend the cycle of regular test. Insist on monitoring the actual operation condition of the circuit breaker, carefully analyze the actual condition of the circuit breaker, timely find existing or potential defects and faults, and carry out targeted local maintenance. For common problems, it is advisable to arrange extended maintenance

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