Definition and difference of load switch, isolation switch, and circuit breaker

Isolation switchis the most commonly used type of High-Voltage Switchgear, as the name suggests, it plays an isolation role in the circuit. Its working principle and structure are relatively simple, but due to its large usage and high reliability requirements, it has a significant impact on the design, establishment, and safe operation of substations and power plants. The main feature of a knife switch is that it has no arc extinguishing ability and can only open and close circuits without load current. Disconnector refers to the insulation distance and clear disconnection mark between the contacts that meet the specified requirements when in the open position; A switch device that can carry the current under normal circuit conditions and the current under abnormal conditions (such as short circuit) within a specified time when in the closed position. The isolation switch we refer to generally refers to a high-voltage isolation switch, which is a type of isolation switch with a rated voltage of 1kV or above. It is commonly referred to as an isolation switch and is the most commonly used type of high-voltage switchgear. Its working principle and structure are relatively simple, but due to its large usage and high reliability requirements, it has a significant impact on the design, establishment, and safe operation of substations and power plants. The main feature of a knife switch is that it has no arc extinguishing ability and can only open and close circuits without load current. Isolation switches are used for various voltage levels, to change circuit connections or isolate lines or equipment from power sources. They do not have the ability to cut off current and can only be operated after disconnecting the line with other equipment. Generally equipped with interlocking devices to prevent accidental operation of switches under load, sometimes pins are needed to prevent the switch from disconnecting under the magnetic force of major faults.

A circuit breaker (English name: circuit breaker) refers to a switching device that can close, carry, and disconnect current under normal circuit conditions, and can close, carry, and disconnect current under abnormal circuit conditions (including short-circuit conditions) within a specified time. Circuit Breakers can be used to distribute electrical energy, start asynchronous motors infrequently, protect power lines and motors, and automatically cut off circuits when they experience serious overload, short circuit, undervoltage, and other faults. Their function is equivalent to a combination of fuse type switches and over/under heat relays. And generally, there is no need to change the components after disconnecting the fault current. At present, it has been widely applied.

The difference between load switch, isolation switch, and circuit breaker:

1. The load switch can be used for load breaking and has a self extinguishing function, but its breaking capacity is very small and limited.

2. Isolation switches are generally not capable of breaking loads. They do not have arc extinguishing enclosures in their structure, and there are also isolation switches that can break loads. However, their structure is relatively simpler compared to load switches.

3. Load switches and isolation switches can both form obvious disconnection points. Most circuit breakers do not have isolation functions, and there are also a few circuit breakers with isolation functions.

4. Isolation switches do not have protective functions, and the protection of load switches is generally achieved by adding fuses, only with quick break and overcurrent protection.

5. The breaking capacity of circuit breakers can be made very high during the manufacturing process. Mainly relying on the use of current transformers in conjunction with secondary equipment for protection. Can have short-circuit protection, overload protection, leakage protection, etc