Operation and maintenance of the hottest 10kV vacu

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Operation and maintenance of 10kV vacuum circuit breakers since the 1980s, China has developed and produced a number of 12kV vacuum circuit breakers with relatively stable performance and put them into operation. At present, in the process of vigorously promoting oil-free equipment in 10kV and below voltage level distribution, vacuum circuit breaker has gradually replaced oil circuit breaker as the main equipment. Since 1996, the 10kv High-voltage cabinet of our bureau has basically adopted vacuum circuit breaker, and gradually transformed the original oil less circuit breaker. Up to now, the operation is in good condition

vacuum circuit breaker is a circuit breaker with vacuum with high insulation strength as the arc extinguishing medium. Its contact opens and closes the circuit in a sealed vacuum chamber. When the contact cuts off the current, only the arc formed by metal vapor ions. Because the diffusion and recombination process of metal vapor ions is very rapid, it can quickly extinguish the arc, restore the vacuum, and withstand multiple opening and closing without reducing the breaking capacity

since the vacuum circuit breaker itself has the characteristics of simple structure, small volume, light weight, long service life, small maintenance and is suitable for frequent operation, the vacuum circuit breaker can be used as the distribution circuit breaker of the transmission and distribution system, the auxiliary power circuit breaker, and the remaining materials in the head of the electric furnace. Steel laws and sheets can be used to sort out the transformer and high-voltage motor. The circuit breaker can also be used to adapt to the capacitor bank

2 problems needing attention in operation and maintenance

(1) vacuum of vacuum interrupter. The vacuum arc extinguishing chamber is the key component of the vacuum circuit breaker. It is supported and sealed by glass or ceramic. There are dynamic and static contacts and shielding covers inside. The indoor vacuum is a negative pressure of ~ PA to ensure its arc extinguishing performance and insulation level during disconnection. With the increase of the service time and the number of interruptions of the vacuum interrupter, as well as the effect of external factors, its vacuum degree gradually decreases, which will affect its interrupting capacity and withstand voltage level to a certain extent. Therefore, the vacuum of the arc extinguishing chamber must be checked regularly during the use of the vacuum circuit breaker. The following two points shall be achieved:

① power frequency withstand voltage test (42KV) shall be conducted regularly. According to the provisions of "preventive test procedures for power equipment" and in combination with the actual situation of our bureau, our bureau requires that the power frequency withstand voltage test must be carried out for the vacuum circuit breaker 0.5, 1, 1.5 and 2 years after putting into operation, and the power frequency withstand voltage test shall be decided once a year or twice a year according to the operation situation after 2 years. At present, the instrument for measuring vacuum by 5 is not perfect, and power frequency withstand voltage is still a more effective method for measuring vacuum

② operators shall regularly patrol the vacuum circuit breaker. Especially for the vacuum arc extinguishing chamber with glass shell, the surface color of its internal components and the color of arc light during breaking current can be visually judged. When the surface color of internal components becomes dark or the arc light is dark red when breaking the current, it can be preliminarily judged that the vacuum has been seriously reduced. At this time, the inspection personnel shall be notified immediately for power failure detection. Tasteless

(2) prevent overvoltage. The vacuum circuit breaker has good breaking performance. Sometimes it cuts off the inductive circuit and extinguishes the arc before the current crosses zero, resulting in cut-off overvoltage, which must be paid attention to. The oil immersed transformer not only has high impulse voltage withstand value, but also has large stray capacitance, so it does not need special protection; For dry-type transformer with low impulse voltage tolerance or electric furnace transformer with frequent operation lag, measures such as installing metal oxide arrester or installing capacitor should be taken to prevent overvoltage

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