The function of the Disconnect switch ( Isolated switch)
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The function of the Disconnect switch ( Isolated switch)

Views: 0     Author: Site Editor     Publish Time: 2021-09-10      Origin: Site


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   Disconnect switch is one of the most used electrical appliances in high-voltage switchgear. As the name suggests, it acts as isolation in the circuit. Its working principle and structure are relatively simple. However, due to the large amount of use and high reliability requirements, it is very greater impact for design, establishment and safe operation of the power plant. The main feature of the switch is that it has no arc extinguishing potential and can only open and close the circuit under the condition of no load current.


Main application

1)After opening, establish a reliable insulation gap, and separate the equipment or lines that need to be overhauled from the power supply with an obvious disconnection point to ensure the safety of overhaul personnel and equipment.

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

3)It can be used to divide and combine the small currents in the circuit, such as the charging current of bushings, bus bars, connectors, short cables, the capacitance current of the switching voltage equalizing capacitor, the circulating current during double bus switching and the excitation current of the voltage transformer 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 the transformer with the necessary capacity.


High-voltage disconnect switch (isolating switches) can be divided into outdoor high-voltage isolating switches and indoor high-voltage isolating switches according to their different installation methods. Outdoor high-voltage isolating switch refers to a high-voltage isolating switch that can withstand the effects of wind, rain, snow, dirt, condensation, ice, and thick frost, and is suitable for installation on the terrace. According to the difference of the insulation pillar structure, it can be divided into single-column disconnector, double-column disconnector, and three-column disconnector. Among them, the single-column isolating switch directly uses the vertical space as the electrical insulation of the fracture under the overhead bus. Therefore, it has obvious advantages that it saves floor space, reduces lead wires, and has a clear opening and closing state. Under the condition of ultra-high voltage transmission, the effect of saving floor space is more significant after the single-column isolating switch is adopted in the substation. Isolating switches are mainly used in low-voltage terminal power distribution systems such as houses and buildings in low-voltage equipment. Main function: Breaking and connecting lines with load




1.During the overhaul of electrical equipment, an electrical compartment is provided, and it is an obvious disconnection point to ensure the personal safety of maintenance personnel.

2. Isolating switches cannot be operated with load: they cannot be operated with rated load or large load, load current and short-circuit current cannot be divided or combined, but those with arc extinguishing chamber can be operated with small load and no-load circuit.

3. In general power transmission operation: first close the isolating switch, then close the circuit breaker or load switch; During power-off operation: first disconnect the circuit breaker or load switch, and then disconnect the isolating switch.

4. The selection is the same as other electrical equipment, and its rated voltage, rated current, dynamic stable current, thermal stable current, etc. must meet the needs of the use occasion.

The function of the isolating switch is to disconnect the circuit without load current. Make the equipment under inspection and the power supply have an obvious disconnection point to ensure the safety of the maintenance personnel. The isolation switch does not have a special arc extinguishing device to cut off the load current and short-circuit current. Therefore, it must be in the condition that the circuit is disconnected by the circuit breaker Only then can the isolation switch be operated. 

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