Load switches, isolating switches, and circuit breakers all carry the rated current of the circuit in the primary circuit. In short, circuit breakers are used to protect circuits. The load switch can disconnect and connect the normal load current of the system, and the role of the isolation switch cannot be ignored. The isolation switch plays a significant role as a disconnection point in the circuit to ensure the safety of maintenance personnel. Let's take a specific look at their functions and differences together.

Purpose of high-voltage isolation switch:

The isolation switch is mainly used to reliably isolate the parts that need to be cut off from the live parts in the high-voltage distribution device, in order to ensure the safety of maintenance work.

The contacts of the isolation switch are all exposed in the air and have obvious disconnection points. The isolation switch does not have an arc extinguishing device, so it cannot be used to cut off load current or short-circuit current. Otherwise, under high voltage, the disconnection point will generate a strong arc and it is difficult to extinguish it on its own. It may even cause arcing (phase to ground or phase to phase short circuit), burn equipment, and endanger personal safety, which is a serious accident called "pulling the isolation switch with load". Isolation switches can also be used to switch certain circuits to change the operation mode of the system.

For example:

In a dual bus circuit, an isolation switch can be used to switch the running circuit from one bus to another. At the same time, it can also be used to operate some small current circuits.

(1) After opening, establish a reliable insulation gap and separate the equipment or line that needs maintenance from the power supply with a clear disconnection point to ensure the safety of maintenance personnel and equipment.

(2) Change the wiring according to operational needs.

The function of high-voltage load switch:

(1) Purpose

High voltage load switch is an electrical appliance with functions between high voltage circuit breaker and high voltage isolation switch. High voltage load switch is often used in series with high voltage fuse; Used to control power transformers. The high-voltage load switch has a simple arc extinguishing device because it can turn on and off a certain amount of load current and overload current. However, it cannot disconnect short-circuit current, so it is usually used in series with high-voltage fuses to provide short-circuit protection.
(2) Characteristics

It can isolate the power supply and has obvious disconnection points, mostly used for fixed high-voltage equipment. There is no arc extinguishing device, which can pass through normal working current and short circuit circuit circuit in the closed state. It is strictly prohibited to connect and disconnect circuits with load, and it is often used in series with high-voltage circuit breakers.

(3) Function

Used for breaking load current and making short-circuit current, used for breaking load current, closed-loop current, no-load transformer and cable charging current, and making short-circuit current. Load switches equipped with grounding switches can withstand short-circuit currents. A load switch fuse combination device with a tripping device and a high breaking capacity fuse is equipped with a phase failure tripping function, which can cut off short-circuit current and serve as a protective device.

High voltage circuit breaker:
A circuit breaker, also known as a high-voltage switch, can not only cut off or close the no-load current and load current in the high-voltage circuit, but also cut off the overload current and short-circuit current through the relay protection device when a system fault occurs.

(1) The Function and Function of Circuit Breakers

High voltage circuit breakers are one of the most important equipment in the power system, used to connect and disconnect circuits under normal conditions, and switch equipment that can quickly disconnect fault currents in case of faults. include:
● Cut off or close the no-load current of high-voltage lines;
Cut off or close the load current of high-voltage lines;
Cut off or close the fault current of the high-voltage line.
(2) Classification and characteristics of circuit breakers

High voltage circuit breakers are mainly divided into multi oil circuit breakers, low oil circuit breakers, sulfur hexafluoride circuit breakers, vacuum circuit breakers, compressed air circuit breakers, etc. Their characteristics are as follows:

1) Multi oil circuit breaker

It is simple to implement and inexpensive, but due to its high oil consumption, large volume, heavy maintenance workload, and susceptibility to explosions and fires.
Multi oil circuit breaker is a high-voltage circuit breaker that uses insulating oil as the arc extinguishing medium and the main insulation medium. Its structure is simple, the process requirements are low, but its volume is large, and it uses more steel and insulating oil.
2) Low oil circuit breaker
It uses less oil and has a small and sturdy fuel tank structure, which has the characteristics of material saving, explosion-proof and fireproof. The use of low oil circuit breakers is safe, greatly simplifying the distribution device, making it small in size and easy to transport.

Low oil circuit breakers have a simple structure, a long history of use, and rich operating experience. Currently, they are still dominant in the power system. Low oil circuit breakers below 20kV produced in China are indoor, while 35kV and above are outdoor.
3) SF6 circuit breaker

Good electrical performance, high fracture voltage. The operation, maintenance, and repair of the equipment are very convenient, with a long maintenance cycle, good breaking performance, and a small floor area, especially for SF6 fully enclosed combination appliances, which can greatly reduce the floor area of the substation.