Detailed explanation of the role and difference between load switch, disconnector and vacuum circuit breaker

First, what is the load switch?

It is a control device with a simple arc extinguishing device that can carry load and circuit. It can interrupt a certain load current and overload current, but can not open the short-circuit current. It must be used in series with the high-voltage fuse to cut off the short-circuit current by means of a fuse.

The role of the load switch :

1. Breaking and closing cooperation. Because it has a certain arc-extinguishing capability, it can be used to break and close the load current and a certain multiple (usually 3-4 times) of overload current; it can also be used to break and close the allowable capacity of the isolation switch. Larger no-load transformers, longer no-load lines, and sometimes used to break and close large-capacity capacitor banks.

2, the substitution effect. A combination of a load switch and a current limiting fuse can be used in place of a circuit breaker . That is, the load switch is responsible for breaking and closing the overload current less than a certain multiple, and the current limiting fuse is responsible for breaking the large overload current and the short circuit current.

3. The load switch and the current limiting fuse are combined in series to form a load switch, which is called “load switch-fuse combination electric appliance” in the national standard. The fuse can be mounted on the power side of the load switch or on the power receiving side of the load switch. When it is not necessary to frequently replace the fuse, the former arrangement should be used in order to utilize the load switch as the function of the isolating switch, which is used to isolate the voltage applied to the current limiting fuse.

Second, what is the isolation switch?

It is a control device without arc extinguishing device. Its main function is to isolate the power supply to ensure the safe maintenance of other electrical equipment, so it is not allowed to operate with load. However, under certain conditions, it is allowed to turn on or off the low power circuit. It is the most and most frequent electrical device used in high voltage switches .

The role of the isolating switch:

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

2. According to the operation needs, change the line.

3. It can be used to divide and combine small currents in the line, such as casing, busbar, connector, short cable charging current, capacitor equalizing capacitor capacitance current, double busbar switching current and voltage transformer excitation current Wait.

4. According to the specific conditions of different structure types, it can be used to divide and combine the no-load excitation current of a certain capacity transformer.

The high-voltage isolating switch can be divided into an outdoor high-voltage isolating switch and an indoor high-voltage isolating switch according to different installation methods.

The outdoor high-voltage isolating switch is capable of withstanding the effects of wind, rain, snow, pollution, condensation, ice and thick frost, and is suitable for installing a high-voltage isolating switch used on a terrace.

According to the different insulation pillar structure, it can be divided into single column isolation switch, double column isolation switch and three column isolation switch. The single-column isolating switch directly uses the vertical space as the electrical insulation of the fracture under the overhead busbar. Therefore, the obvious advantage is that it saves the floor space and reduces the lead wire, and the closing state is particularly clear. In the case of ultra-high voltage transmission, after the single-column isolating switch is used in the substation, the effect of saving floor space is more significant.

In the low-voltage equipment, the isolating switch is mainly suitable for low-voltage terminal distribution systems such as residential buildings and buildings.

Main function: with load breaking and connecting lines.

3. What is a vacuum circuit breaker?

Because the arc extinguishing medium and the insulating medium of the contact gap after arc extinguishing are high vacuum, it is named; it has the advantages of small volume, light weight, suitable for frequent operation, arc extinguishing without overhaul, and is applied in the distribution network. universal.

The vacuum circuit breaker is an indoor power distribution device in a 3～10kV, 50Hz three-phase AC system, which can be used for protection and control of electrical equipment in industrial and mining enterprises, power plants and substations , especially suitable for oil-free and less For maintenance and frequent operation, the circuit breaker can be configured in the central cabinet, double cabinet, and fixed cabinet for controlling and protecting high voltage electrical equipment.

1 vacuum circuit breaker working principle

When the moving and static contacts are opened under the action of the operating mechanism, an arc is generated between the contacts, and the surface of the contact volatilizes steam at a high temperature. Since the contact is designed to have a special shape, a magnetic field is generated when the current passes, and the arc is Under the action of the magnetic field, it moves rapidly along the tangential direction of the contact surface, and some metal vapor is condensed on the metal cylinder (shield). The arc is extinguished when the natural zero-crossing occurs, and the dielectric strength between the contacts is quickly recovered.

2 vacuum circuit breaker function

The circuit breaker has overload, short circuit and under voltage protection functions, and has the ability to protect the line and power supply.

Fourth, the difference between the load switch and the isolating switch

The first difference is that the currents cut by the two are not the same.

Because the isolating switch does not have an arc extinguishing device, it is only suitable for cutting off the no-load current, and cannot cut off the load current and short-circuit current. Therefore, the isolating switch device can only operate safely when the circuit is safely disconnected, and is rigorously Load operation to avoid a safety accident. Since the load switch has an arc extinguishing device, it can overload current and rated load current, but the short circuit current cannot be cut off.

The second point is that the load switch has an arc extinguishing device, and the isolating switch does not have such a device.

So is there any difference between this arc extinguishing device? The so-called arc extinguishing device is to better help the opening and closing of the switchgear, and can also effectively limit the arc and help the arc to extinguish. There is such an arc extinguishing device, which is safer for the switchgear. Therefore, most of the switching devices are made of arc extinguishing devices. Especially for household use switchgear.

The third point has a different effect.

Because there is no arc extinguishing device, the isolating switch can only be applied to the part of the high voltage circuit device that needs to be charged and the part that needs to be powered off to perform an isolation function, so as to ensure the maintenance and inspection of the high voltage circuit by personnel, and to ensure the safety of personnel.

The load switch is applied to a fixed high-voltage device, which can cut off the fault current and the rated current in the high-voltage device, so the roles of the two are different, but both are applied to the high-voltage device.

Five, the difference between high-voltage load switch and vacuum switch

1. The high-voltage load switch can be disconnected with load and has self-extinguishing function, but its breaking capacity is very small.

2. The high-voltage isolating switch can't be disconnected with load. There is no arc-extinguishing cover on the structure, and there is also an isolating switch that can break the load, but the structure is different from the load switch, which is relatively simple.

3. High-voltage load switch and high-voltage isolating switch can form obvious disconnection points. Most circuit breakers do not have isolation function, and a few circuit breakers have isolation function.

4. The high-voltage isolating switch does not have the protection function. The protection of the high-voltage load switch is generally protected by a fuse, only the quick-break and over-current.

5. The breaking capacity of the high voltage circuit breaker can be made very high during the manufacturing process. Mainly rely on the current transformer to protect the secondary equipment. It can have short circuit protection, overload protection, leakage protection and other functions.

The high-voltage load switch is an electrical function between the high-voltage circuit breaker and the high-voltage isolating switch. The high-voltage load switch is often used in series with the high-voltage fuse; it is used to control the power transformer . The high-voltage load switch has a simple arc extinguishing device because it can switch a certain load current and overload current. However, it cannot break the short-circuit current, so it is generally used in series with the high-voltage fuse, and the fuse is used for short-circuit protection.

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