How to choose high voltage circuit breaker high voltage circuit breaker

Lead: Before entering the text, first learn about what is a high voltage circuit breaker with Xiaobian. Although the term high-voltage circuit breaker is very strange, it seems that life does not need to touch these. In fact, the high-voltage circuit breaker is simply an important control and protection device, which is mainly used in power plants, substations and power systems. in. Given its pivotal role, how do you choose the right high voltage circuit breaker? The following small series will be introduced for everyone.

The general principle is to ensure the safety of high-voltage electrical appliances under normal operation, maintenance, short-circuit and over-voltage conditions. High-voltage electrical appliances should be selected according to the following conditions:

1 According to the normal working conditions including voltage, current, frequency, mechanical load and other options.

2 According to the short-circuit conditions, including short-time withstand current, peak withstand current, closing and breaking current.

3 According to environmental conditions, including temperature, humidity, altitude, earthquake, etc.

4 According to the ability to withstand overvoltage, including insulation level.

5 According to the different characteristics of various types of high-voltage electrical appliances, including the operating performance of the switch, the protection characteristics of the fuse, the load and accuracy of the transformer, etc., choose the different types of high-voltage short-circuit oil circuit breaker oil circuit breaker according to the amount of oil used. Divided into two types of oil and less oil.

The oil in the multi-oil circuit breaker acts both as insulation and arc extinguishing; the oil in the oil-less circuit breaker acts only as an arc extinguishing medium. When the circuit breaker trips, an arc is generated, and the arc is quickly extinguished under the combined action of oil blowing by the cross flow, longitudinal blowing and mechanical movement of the oil flow. Multi-oil circuit breakers have been eliminated due to their large amount of oil, large volume, large amount of steel, slow moving speed, large maintenance workload, inconvenient installation and handling, large floor space and fire. However, there are still a small number of 35kV substations in China that still use multi-oil circuit breakers.

The oil-less circuit breaker has the advantages of simple structure, less oil consumption, small volume, safe operation and a large amount of oil and steel. The main use now is the SN10-10 type oil-less circuit breaker, which is divided into I, II and III according to its current-cut capacity, and its size is 300MVA, 500MVA and 750MVA.

Due to the poor breaking performance of the oil-less circuit breaker and the flammability and explosiveness of the oil, it is gradually being eliminated. Newly built substations generally use vacuum circuit breakers or sulphur hexafluoride circuit breakers. Sulfur hexafluoride circuit breaker SF6 circuit breaker is a circuit breaker that uses sulphur hexafluoride (SF6) gas as insulation and arc extinguishing medium. It is a new type of circuit breaker developed after the 1950s. Due to its excellent insulation properties and arc-extinguishing properties, SF6 gas develops rapidly. It can be used in 6~500kV systems, and is currently used mainly in power systems of 110kV and above.

The structure of the circuit breaker arc extinguishing chamber is a gas pressure type, a self-energizing arc extinguishing type (spin arc type, thermal expansion type) and a mixed arc extinguishing type. The LN1 and LN2 SF6 circuit breakers produced in China are compressed air arc extinguishing structures, and the LW3 outdoor SF6 circuit breakers adopt a suspension arc extinguishing structure. The operating mechanism of the SF6 circuit breaker mainly adopts spring and hydraulic operating mechanism.

(sf6 circuit breaker)

Vacuum circuit breaker

Vacuum circuit breakers are circuit breakers that use vacuum as an insulation and arc extinguishing medium. Vacuum circuit breakers are divided into indoor and outdoor types according to the installation location; vacuum circuit breakers are ideal equipment for substation to achieve oil-free transformation. Currently used mainly in power supply systems of 35kV and below. The contacts of the vacuum circuit breaker are disc-shaped and placed in a vacuum interrupter. When the contact is just separated, since there is no gas that can be freed in the vacuum, only high electric field emission and hot electron emission cause a vacuum arc between the contacts. The temperature of the arc is very high, so that the metal surface forms metal vapor. Because the contact is designed to have a special shape, a transverse magnetic field is generated when the current passes, so that the vacuum arc moves rapidly in the tangential direction of the main contact surface, and the arc naturally crosses zero, the arc Temporarily extinguished, the dielectric strength between the contacts recovers quickly; after the current crosses zero, the applied voltage is restored, but the contact gap is no longer broken, and the vacuum arc can be extinguished when the current crosses zero for the first time.

The high-voltage circuit breaker is like a protector of circuit protection at all times, paying attention to abnormalities in the circuit. Once the situation occurs, it will unscrupulously cut off the circuit to protect the security. Choosing the right circuit breaker is like choosing the right bodyguard to protect you. However, choosing the wrong one is undoubtedly like buying an untimely bomb. The safety problem cannot be taken lightly, and the hidden danger is fierce. Therefore, Xiao Bian reminds readers that the choice of circuit breakers must be cautious and purchase regular and guaranteed products.