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Switch-Disconnector Function
- Sep 08, 2017 -

The isolating switch is a switching device which is mainly used for "isolating power, switching operation, connecting and cutting small current circuit", without extinguishing the arc function. When the isolating switch is in the split position, the contact between the contact can meet the required insulation distance and the obvious disconnecting mark; A switching device that can carry the current under normal loop conditions and the current under the specified time, such as a short circuit. Generally used for high pressure isolating switch, the rated voltage 1 kv disconnecting switch, its working principle and structure is simple, but, because of the large amount work reliability requirement is high, the design of substation, power plant, set up and the influence of the safe operation of the larger. The main feature of the isolation switch is the unquenching ability, which can only be divided and closed without load current. The article introduces the function, characteristic, type, application, error prevention improvement, maintenance and common problems of the isolation switch.


1. After the breaking of the brake, establish reliable insulation clearance, and the equipment or circuit that will need to be overhauled shall be separated from the power supply by an obvious cut-off point to ensure the safety of maintenance personnel and equipment.

2. Replace the wiring according to the operation needs.

3, can be used to points, small current in a circuit, such as casing, busbar cables, connectors, short charging current, pressure switch capacitance of capacitive current, double bus exchange when the circulation of the excitation current and voltage transformer, etc.

4. According to the specific situation of different structure types, the no-load excitation current of transformer can be divided and combined.

The isolation switch mainly applies to low - voltage terminal power distribution system in low - voltage equipment. Main function: no load breaking and connecting line.

1. To isolate the power supply, disconnect the high voltage overhaul equipment and the electrified equipment, so that there is a visible disconnection point.

2. The isolation switch and the circuit breaker cooperate, and the operation mode of the system shall be operated on the reverse brake to change the system operation wiring mode.

3. To connect or disconnect the small current circuit.

A set of isolation switches are installed on the two sides of the circuit breaker before and after the circuit breaker. The purpose is to isolate the circuit breaker and the power source to form an obvious disconnection point. Because the original circuit breaker USES oil circuit breaker, oil circuit breaker needs to be constantly overhauled, so the two sides should have obvious disconnection point to facilitate maintenance. Under normal circumstances, the outlet tank from the bus through the switch cabinet power down, needs a set of isolating switch in front of the circuit breaker is isolated from the power, but sometimes, the back of the circuit breaker may also have chemistry, such as through other loop of send, capacitor devices such as the send, so it need a group of isolating switch at the back of the circuit breaker.

The isolation switch is mainly used to isolate the parts of the high-voltage power distribution devices from the live parts and the electric parts, so as to ensure the safety of the maintenance work. Isolating switch contact all exposed in the air, has obvious disconnect point, isolating switch no arcing devices, therefore cannot be used to cut off the load current or short circuit current, otherwise under the effect of high pressure, the disconnect will produce strong arc, and difficult to put out by oneself, even may cause arcing (relative or interphase short circuit), burning equipment, endanger personal safety, this is known as "load pull isolating switch" serious accidents. The isolation switch can also be used to switch operations on certain circuits to change the way the system works. For example, in a two-bus circuit, a separate switch can be used to switch the running circuit from one bus to another. It can also be used to manipulate small current circuits.


1. Provide an electrical separation during overhaul of electrical equipment and a visible disconnection point to ensure the safety of the maintenance personnel.

2. Isolating switch can't load operation: can't take the rated load and large load operation, not points, load current and short-circuit current, but have the arcing chamber can be operated with small load and no load circuit.

3. General electric power supply operation: first, the disconnecting switch, after the circuit breaker or the load type switch; Power failure operation: disconnect circuit breaker or load switch before disconnecting switch.

4. As with other electrical equipment, the rated voltage, rated current, dynamic stable current and thermal stable current must meet the needs of the use.

The function of isolating switch is disconnected no-load current of the circuit. Make the maintenance of equipment and power supply is an obvious disconnect point, to ensure the safety of maintenance personnel, there is no specific arc extinguishing device isolating switch can't cut off the load current and short circuit current, so you have to disconnect the circuit in the circuit on the circuit breaker can operate under the condition of isolating switch.