What is a circuit breaker, what is a load switch, and what is a disconnector? And what is the difference
We all know that circuit breakers are switching devices that can close, carry, and break the current under normal circuit conditions, and can close, carry, and break the current under abnormal circuit conditions (including short circuit conditions) within a specified time. A load switch is a switching device located between a circuit breaker and an isolation switch, with a simple arc extinguishing device that can cut off the rated load current and a certain overload current, but cannot cut off the short-circuit current. A disconnector is a circuit that disconnects no-load current, causing a clear disconnection point between the maintenance equipment and the power supply, thereby ensuring the personal safety of maintenance personnel. The disconnector does not have a dedicated arc extinguishing device, so it cannot cut off load current and short-circuit current. Therefore, the operation of the disconnector must be carried out only when the circuit breaker is disconnected.
What is the difference between circuit breakers, load switches, and disconnectors?
Load switch: It is a switching device that can switch on and off load current, excitation current, charging current, and capacitor bank current under normal working conditions.
There are six main types of high-voltage load switches:
① Solid gas generation high-voltage load switch: utilizing power on and off
The energy of the arc itself causes the gas producing material in the arc chamber to produce gas to blow out the arc. Its structure is relatively simple and suitable for products with a voltage of 35 kV and below.
② Compressed air high-pressure load switch: It uses the compressed air of the piston during the breaking process to blow out the arc, and its structure is relatively simple, suitable for products with a voltage of 35 kV and below.
③ Compressed air type high-voltage load switch: using compressed air
Gas blown arc extinguishing can break large currents, and its structure is relatively complex, suitable for products of 60 kV and above.
④ SF type high-voltage load switch: using SF gas to extinguish the arc,
It has a large breaking current and good breaking capacitor current performance, but its structure is relatively complex, suitable for products with a voltage of 35 kV and above.
⑤ Oil immersed high-voltage load switch: Utilizing the energy of the arc itself to decompose and vaporize the oil around the arc and cool it to extinguish the arc. Its structure is relatively simple, but its weight is large, and it is suitable for outdoor products of 35 kV and below.
⑥ Vacuum type high-voltage load switch: uses vacuum medium to extinguish arc, with a long electrical life and relatively high price, suitable for products with a voltage of 220 kV and below.
And low-voltage load switches are also known as switch fuse groups. Suitable for AC power frequency circuits, to manually switch on and off load circuits infrequently; It can also be used for overload and short circuit protection of circuits. The power outage route is completed by the contact knife, and the overload and short circuit protection is completed by the fuse.
disconnector: refers to the insulation distance and obvious disconnection marks between the contacts that meet the specified requirements when in different positions; When in the closed position, a switchgear capable of carrying the current under normal circuit conditions and the current under abnormal conditions (such as short circuits) within a specified time.
High voltage disconnector can be divided into outdoor high voltage isolation switches and indoor high voltage isolation switches according to their installation methods. Outdoor high-voltage isolation switch refers to a device that can withstand the effects of wind, rain, snow, dirt, condensation, ice, and thick frost, and is suitable for installation in the open air
According to the different insulation pillar structures, it can be divided into single column disconnectors, double column disconnectors and Three column disconnector. The single column disconnector directly uses the vertical space below the overhead bus as the electrical insulation of the fracture. Therefore, it has the obvious advantage of saving the floor area, reducing the lead wire, and at the same time, the state of the opening and closing room is particularly clear. In the case of ultra-high voltage transmission, the Electrical substation uses the single column disconnector to save
The effect of occupying an area is more significant. In low-voltage equipment, it is mainly suitable for low-voltage terminal distribution systems such as residential buildings and buildings. Main function: on-load breaking and connection
Circuit breaker: A switching device that can close, carry, and break the current under normal circuit conditions, and can close, carry, and break the current under abnormal circuit conditions (including short circuit conditions) within a specified time.
Due to regulations requiring clear disconnection points in some circuits, load switches can be used separately because obvious disconnection points can be seen in the circuit. Circuit breakers generally need to be used in conjunction with isolation switches to ensure clear disconnection points in the circuit. Isolation switches cannot be operated with load, meaning that they cannot be opened or closed when the isolation switch cannot be powered on. Load switches, as the name suggests, It can be operated with load, that is, it can be opened and closed first when powered on.
High voltage circuit breaker is the main power control equipment in power plant, Electrical substation, distribution room, etc. It has arc extinguishing characteristics. When the system operates normally, it can cut off and connect the no-load and load current of lines and various electrical equipment; When the system malfunctions
When combined with relay protection, it can quickly cut off fault current to prevent expanding the scope of accidents.
Therefore, the operation of high-voltage circuit breakers directly affects the safe operation of the power system; There are many types of high-voltage circuit breakers, which can be divided into oil circuit breakers (more oil circuit breakers, less oil circuit breakers), Sulfur hexafluoride circuit breakers (SF6 circuit breakers), vacuum circuit breakers, compressed air circuit breakers, etc. And low-voltage circuit breakers are also divided into MCCB and ACB, which are electrical appliances that have both manual switching functions and automatic protection against voltage loss, undervoltage, overload, and short circuit. It can be used to distribute electrical energy, infrequently start asynchronous motors, protect power lines and motors, and automatically cut off circuits in case of severe overload, short circuit, and undervoltage faults. Its function is equivalent to a combination of fuse switches and over/under heat relays. Moreover, after breaking the fault current, there is generally no need to change the components, which has been widely used.
What is the difference between circuit breakers, load switches, and disconnector?
1. The load switch can be disconnected with load and has a self extinguishing function, but its breaking capacity is very small and limited.
2. Disconnectors are generally not capable of breaking with load, and there is no arc extinguishing cover in the structure. There are also isolation switches that can break the load, but the structure is different from the load switch and relatively simpler.
3. Both load switches and disconnectors can form obvious disconnection points. Most circuit breakers do not have isolation functions, and there are also a few circuit breakers with isolation functions.
4. The disconnector does not have a protection function, and the protection of the load switch is usually protected by adding a fuse, only with quick break and overcurrent
5. The breaking capacity of circuit breakers can be very high during the manufacturing process. Mainly relying on the addition of current transformers in conjunction with secondary equipment for protection. It can have functions such as short circuit protection, overload protection, and leakage protection.
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