01
What is an isolating switch
Isolating switch, also known as knife switch, is a kind of high voltage switch. It has no arc extinguishing device. When it is in the closed position, it can carry working current, but it cannot be used to connect or cut off load current and short-circuit current. Should be matched with the circuit breaker.
02
The purpose of the isolating switch
（1）Isolation voltage:
When performing maintenance, use an isolating switch to isolate the electrical equipment from the running grid to form a visible disconnection gap to ensure the safety of operation and maintenance.
（2）Switching operation:
Put in the spare bus or bypass bus and change the operation mode, and use the isolating switch to cooperate with the circuit breaker to complete.
In the double-bus wiring mode, the connection element is switched between the two busbars by using the on-off positions of the isolating switches on the two busbars.
（3）Turning on and off the small current circuit:
The isolating switch has a certain ability to make and break small inductance current and capacitance current. The isolating switch can be used to perform the following operations during operation:
① It can be used to connect and disconnect voltage transformers and arresters.
② Connect and disconnect no-load lines with a capacitance current of no more than 5A, with a voltage of 10kV and no-load transmission lines with a length of less than 5km and no-load transmission lines with a voltage of 35kV and a length of 10km.
③ Switching on and off the no-load transformer with the excitation current not exceeding 2A:35kV class is less than 1000kVA, 110kV class is less than 3200kVA.
④ Automatic fast isolation:Under certain conditions, it can quickly isolate the equipment and lines that have failed, so as to save the consumption of circuit breakers.
3. Classification of isolation switches
（1）According to the installation location, it is divided into: indoor type and outdoor type.
（2）According to the number of insulating pillars, it is divided into: single-pillar, double-pillar and plug-in.
（3）According to the movement mode, it is divided into: horizontal rotation type, vertical telescopic type, swing type and plug-in type.
（4）According to whether there is a grounded switch, it is divided into two types: grounded switch and without grounded switch.
（5）According to the operating mechanism, it is divided into manual, electric and pneumatic.
4. The composition of the isolating switch
The isolating switch is composed of conductive part, insulating part, transmission part, operating mechanism, base and ground knife.
（1）About conductive parts
The conductive part is fixed on the base through the supporting insulator, used to connect and disconnect the circuit, mainly including the knife switch (moving contact or conductive rod) driven and rotated by the operating insulator, the static contact fixed on the base and the Connect the busbar or the terminal of the device.
（2）About the insulation part
There are two main types of isolation switch insulation: ground insulation and fracture insulation.
Ground insulation is generally composed of post insulators and operation insulators. They usually use porcelain insulators, and some also use epoxy resin or epoxy glass cloth boards as insulating materials.
Fracture insulation has obvious visible gap fracture insulation, usually with air as the insulating medium. After the isolating switch is disconnected, the breakdown voltage between the fractures must be greater than the breakdown voltage between the opposite ground.
In this way, when a dangerous overvoltage occurs in the circuit, the first is to discharge relatively, so as to prevent the fracture between the contacts from being broken down first, and to ensure the safety of maintenance personnel.
（3）About the transmission part
The operating mechanism controls the opening and closing of the knife and the brake through the transmission device. The transmission mechanism accepts the operating force of the operating mechanism, and transmits it to the contacts to realize opening and closing by means of a crank arm, a connecting rod, a shaft gear, and an operating insulator.
According to operation needs, three-phase linkage or split-phase operation can be adopted.
（4）About the operating mechanism
Provide energy for the action of the isolating switch through various methods.
（5）About the base and the ground knife
The base is usually fixed on the frame or wall with screws.
For more information on isolation switches, please feel free to call Slocable at 86-769-22010201. You can also email us at pv@slocable.com.cn.
