The difference between a load switch, an isolation switch, and a vacuum circuit breaker

What is a load switch?

It is a control appliance with a simple arc extinguishing device that can be load divided and combined with a circuit. It can cut off a certain load current and overload current, but it cannot disconnect the short circuit current. It must be used in series with a high voltage fuse to remove the short circuit current with the help of a fuse.

The role of the load switch:

  1. Disruption and relational effects

Since it has a certain arc extinguishing ability, it can be used to switch off and close the load current and the overload current of a certain multiple (usually 3-4 times); it can also be used to shut off and close unloaded transformers with a larger capacity than isolating switches, longer unloaded lines, and sometimes also used to shut off and close large-capacity capacitor groups.

  1. Alternative effects.

The BWC-12-630-20 Gis Load Switch can be used in tandem with a current limiting fuse instead of a circuit breaker. That is, the load switch bears the overload current that is less than a certain multiple of the opening and closing, while the current limiting fuse bears the larger overload current and short circuit current.

  1. Load switch combined in series

A load switch that combines a load switch and a current limiting fuse in series is defined as a “load switch-fuse combination appliance” in the national standard. The fuse can be mounted on the BWC-12-630-20 Gis Load Switch

The power supply side can also be installed on the receiving side of the load switch. When the fuse does not need to be replaced frequently, it is advisable to use the previous arrangement so that the load switch also functions as an isolation switch to isolate the voltage applied to the current limiting fuse.


What is an isolation switch?

It is a control appliance without an arc extinguishing device. Its main function is to isolate the power supply to ensure the safety maintenance of other electrical equipment, so it is not allowed to operate with a load. However, under certain conditions, it is permissible to switch on or off a low-power circuit. It is the most used and most frequently used electrical device among high-voltage switches

The role of the isolation switch:

  • After splitting the gate, establish a reliable insulation gap, and separate the equipment or circuit to be overhauled from the power supply with a clear disconnection point to ensure the safety of maintenance personnel and equipment.
  • Switch the lines according to the operating requirements.
  • It can be used to divide and combine small currents in the circuit, such as the charging current of the sleeve, bus, connector, and short cable, the capacitor current of the switching uniform capacitor, the circulation when the double bus is switched, and the excitation current of the voltage transformer.
  • According to the specific conditions of different structural types, it can be used to divide and combine the no-load excitation current of a certain capacity transformer.

According to the different installation methods, high-voltage isolating switches can be divided into outdoor high-voltage isolating switches and indoor high-voltage isolating switches.

An outdoor high-voltage isolation switch is a high-voltage isolation switch that can withstand the effects of wind, rain, snow, dirt, condensation, ice and heavy frost, etc., and is suitable for use on patios.

According to its different insulation pillar structure, it can be divided into single-column isolating switches, double-column isolating switches, and three-column isolating switches. Among them, the single-column isolator switch directly uses the vertical space under the overhead bus as electrical insulation for the broken port. Therefore, it has obvious advantages, which is that it saves floor space, reduces the lead wire, and the split and 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 even more remarkable.

Isolation switches are mainly used in low-voltage equipment for low-voltage terminal power distribution systems such as residential homes and buildings.


What is a vacuum circuit breaker?

It is named because both the arc extinguishing medium and the insulating medium in the contact gap after arc extinguishing are high vacuum; it has the advantages of small size, light weight, suitable for frequent operation, and arc extinguishing without maintenance, and is widely used in distribution networks.

Vacuum circuit breakers are indoor power distribution devices in 3-10kV, 50Hz three-phase AC systems. They can be used for protection and control of electrical equipment in industrial and mining enterprises, power plants, and substations. They are particularly suitable for use requiring no petroization, less maintenance and frequent operation. Circuit breakers can be configured in central cabinets, double-layer cabinets, and fixed cabinets to control and protect high-voltage electrical equipment.


     1.The working principle of a vacuum circuit breaker

When the moving and static contacts split under the action of the operating mechanism, an electric arc is generated between the contacts, and the contact surface volatilizes steam at high temperature. Since the contact is designed to be specially shaped, a magnetic field is generated when current passes. The arc moves rapidly in the tangent direction of the contact surface under the action of this magnetic field, condenses part of the metal steam on the metal cylinder (shield), and the arc is extinguished when it naturally passes zero Now, the strength of the medium between the contacts is fast Get back up.

    2.Vacuum circuit breaker function

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


Difference between load switch and isolation switch

    1.The current cut off by the two is not the same.

Because the isolator switch does not have an arc extinguishing device, it is only suitable for cutting off the unloaded current. The load current and short circuit current cannot be cut off. Therefore, the isolating switch can only be operated safely when the circuit is safely disconnected, and it is strictly operated with load, so as not to cause safety accidents. Since the BWC-12-630-20 Gis Load Switch has an arc extinguishing device, it can overload current and rated load current, but the same cannot cut short circuit current.

   2.The load switch has an arc extinguishing device, and no isolation switch.

So what’s the difference between having this arc extinguishing device or not? The so-called arc extinguishing device is designed to better help the disconnection and closure of switching appliances. It can also effectively limit the arc and help the arc to be extinguished. With such an arc extinguishing device, it is safer for switching appliances. Therefore, most switching appliances are equipped with arc extinguishing devices. In particular, switching appliances for household use.


   3.two have different roles

Since there is no arc extinguishing device, the isolation switch can only be used to isolate the part of the high-voltage circuit device that needs to be charged and the part that requires a power outage, so as to ensure the maintenance and inspection of the high-voltage circuit by personnel and ensure the safety of personnel.

The load switch, on the other hand, is used in fixed high-voltage equipment. It can cut off the fault current and rated current in high-voltage equipment, so the two have different effects, but both are used in high-voltage equipment.


The difference between a high voltage load switch and a vacuum circuit breaker

  • The high voltage load switch can be divided with load and has a self-destructing arc function, but its switching capacity is very small and very limited.
  • High voltage isolators generally cannot be separated with a load. There is no arc extinguishing cover in the structure, and there are also isolating switches that can break the load. However, the structure is different from the load switch, and it is relatively simple.
  • Both the high voltage load switch and the high voltage isolation switch can form an obvious disconnection point. Most circuit breakers do not have an isolation function, and a few circuit breakers also have an isolation function.
  • The high voltage isolation switch does not have a protective function. The protection of a high voltage load switch is generally protected by a fuse, only quick break and overcurrent.
  • The breaking capacity of high voltage circuit breakers can be very high during the manufacturing process. It mainly relies on a pressurized current transformer and a secondary device to protect it. It can have functions such as short circuit protection, overload protection, and leakage protection.


A high voltage load switch is an electrical appliance that functions between a high voltage circuit breaker and a high voltage isolation switch. A high voltage load switch is often used in series with a high voltage fuse; it is used to control power transformers. The high voltage load switch has a simple arc extinguishing device because it can shut off certain load current and overload current. However, it cannot disconnect the short circuit current, so it is generally used in series with a high voltage fuse, and a fuse is used for short circuit protection.

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