The Role Of Isolating Switch, Load Switch And Vacuum Circuit Breaker In High Voltage Distribution Line

Isolating 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. Therefore, it is not allowed to operate with load. However, under certain conditions, it is allowed to connect or disconnect low-power circuits. It is the most used and most frequently used electrical device among high-voltage switches.

Functions of isolating switch:
1. After opening the gate, establish a reliable insulation gap to separate the equipment or line to be repaired from the power supply with an obvious disconnection point to ensure the safety of maintenance personnel and equipment.
2. Switch the line according to the operation needs.
3. It can be used to separate and close small currents in the line, such as the charging current of bushings, busbars, connectors, short cables, the capacitive current of switch equalizing capacitors, the circulating current during double busbar switching, and the excitation current of voltage transformers.
4. According to the specific conditions of different structural types, it can be used to separate and close the no-load excitation current of a certain capacity transformer.

Classification:
High Voltage Disconnect Switch According to the different installation methods, it can be divided into outdoor High Voltage Disconnect Switch and indoor High Voltage Disconnect Switch.
Outdoor High Voltage Disconnect Switch refers to High Voltage Disconnect Switch that can withstand wind, rain, snow, dirt, condensation, ice and thick frost, and is suitable for installation on the terrace.

According to the different insulating support structures, it can be divided into single-column disconnectors, double-column disconnectors, and three-column disconnectors.
Among them, the single-column disconnector directly uses the vertical space under the overhead bus as the electrical insulation of the break. Therefore, it has the obvious advantages of saving floor space, reducing the lead-in wires, and the opening and closing status is particularly clear. In the case of ultra-high voltage transmission, the effect of saving floor space is more significant after the substation adopts a single-column disconnector.

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

Load switch
It is a control device with a simple arc extinguishing device that can open and close circuits with load. It can switch on and off a certain load current and overload current, but cannot disconnect short-circuit current. It must be used in series with a high-voltage fuse to cut off the short-circuit current with the help of a fuse.

Functions of load switch:
1) Opening and closing.
Because it has a certain arc extinguishing ability, it can be used to open and close load current and overload current of a certain multiple (usually 3-4 times); it can also be used to open and close unloaded transformers with a larger capacity than the isolation switch, longer unloaded lines, and sometimes used to open and close large-capacity capacitor banks.
2) Substitution.
The combination of load switch and current-limiting fuse in series can replace the circuit breaker. That is, the load switch is responsible for opening and closing overload currents less than a certain multiple, while the current-limiting fuse is responsible for opening and closing larger overload currents and short-circuit currents.
3) The load switch that is combined in series with the current-limiting fuse is called "load switch-fuse combination electrical appliance" in the national standard.
The fuse can be installed on the power supply 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 adopted so that the load switch can also function as an isolating switch to isolate the voltage applied to the current-limiting fuse.