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Date：04-26-2022
The load switch is a switching appliance between the circuit breaker and the isolating switch. It has a simple arc extinguishing device, which can cut off the rated load current and a certain overload current, but cannot cut off the short-circuit current.
The load switch is mainly used to break and close the load current, and the load switch can also be used in conjunction with the high-voltage fuse to replace the circuit breaker. Because the load switch is easy to use and the price is reasonable, the load switch is widely used in the 10kV distribution network system. Reasonable selection of load switches in the design is of great significance to ensure the safe and reliable operation of the power grid.
The working process of the load switch is as follows: when the brake is opened, under the action of the opening spring, the main shaft rotates clockwise. On the one hand, the piston moves upward through the crank-slider mechanism to compress the gas; on the other hand, through the two sets of four-bar linkage mechanism The formed transmission system makes the main knife open first, then pushes the arc extinguishing knife to open the arc contact, and the compressed air in the cylinder blows out the arc through the nozzle.
The working principle of a high voltage load switch is similar to that of a circuit breaker. Generally, a simple arc extinguishing device is installed, but its structure is relatively simple. The picture shows a compressed air high pressure load switch. Its working process is as follows: when the brake is opened, under the action of the opening spring, the main shaft rotates clockwise. On the one hand, the piston moves upward through the crank-slider mechanism to compress the gas.
On the other hand, through the transmission system composed of two sets of four-bar linkage mechanism, the main knife is opened first, and then the arc-extinguishing knife is pushed to open the arc contact, and the compressed air in the cylinder blows out the arc through the nozzle. When closing, through the main shaft and the transmission system, the main blade and the arc-extinguishing blade rotate clockwise at the same time, and the arc contact is closed first; the main shaft continues to rotate, so that the main contact is closed later.
During the closing process, the opening spring stores energy at the same time. Since the load switch cannot break the short-circuit current, it is often used in combination with the current-limiting high-voltage fuse. The current-limiting function of the current-limiting fuse can not only complete the task of breaking the circuit, but also significantly reduce the heat caused by the short-circuit current. and electric power.
