Circuit breaker is an electric appliance in power system, which can automatically disconnect when the line or substation is short circuit or overload to protect the power equipment and personal safety.
High voltage circuit breaker is mainly composed of arc extinguishing system, interrupting system, control device and monitoring element.
If the switch can not be disconnected in time, the electrical device or electronic component will cut off the fault point automatically to protect the personal safety and equipment safety.
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I、Arc extinguishing system
The arc extinguishing system of high voltage circuit breaker includes arc generating device, arc extinguishing device and arc extinguishing chamber.
In the low voltage system, usually uses the air interrupter to extinguish the arc, because in the air interrupter does not have the electric current, therefore cannot have the arc to produce.
In high voltage system, vacuum arc extinguishing is usually used, using the thermal effect and electromagnetic force of current in vacuum arc extinguishing chamber.
In HVDC circuits, arc extinguishing is often done by mechanical extrusion because of large DC current and easy occurrence of arc explosion.
Because of the large volume of high voltage circuit breaker, air arc extinguishing chamber is mostly used.
II、 Disconnection system
The breaker of high voltage circuit breaker mainly includes electromagnet, electromagnetic coil, etc.
The function of an electromagnet is to produce a magnetic field that presses the arc against the yoke.
The function of the electromagnetic coil is to send the pulse signal when the switch is turned on or off to the controller, and the controller completes the disconnecting operation by controlling the electromagnetic coil to turn on or off.
The electromagnetic coil also acts as electromagnetic isolation.
A yoke is mounted on the circuit breaker, which causes the arc voltage to generate a magnetic field on the yoke, which is supplied by a pair of synchronously rotating armatures, thereby preventing the arc from being carried off the circuit by the yoke and causing an accident.
III、 Control devices
Circuit breakers generally adopt special control devices, such as microcomputer circuit breakers (microcomputer protection devices), with control and protection functions.
The function of the microcomputer protection device is to generate voltage or current signal in the circuit when there is a fault, then convert it into electric signal or pulse signal through amplifying circuit, and realize the circuit breaker operation function through relay or other control elements (such as reactor, isolator, etc.).
In addition, there are some mechanical switches used for automatic control switch operation, such as SCR, SCR rectifier diodes, etc.
In order to improve reliability and safety, microcomputer protection devices often use analog output devices to provide more protection functions, such as analog input/output (AFD), voltage/current combination (AVR) or current transformer voltage sampling.
IV、 Monitoring components
The circuit breaker is equipped with a set of automatic monitoring components, which are mainly used to detect the abnormal situation in the process of circuit breaker breaking.
Common high-voltage circuit breakers are SF6, SF7, vacuum and other types, according to different types can be divided into rated voltage 1000V, 1100V and 2000V.
With the development of science and technology, HV circuit breakers are constantly updated. At present, SF6 circuit breaker and SF7 circuit breaker are widely used in our country.
V、 Installation requirements and precautions for high voltage circuit breakers
When installing the high voltage circuit breaker, attention shall be paid to the height of the installation position and the distance; the corresponding wiring mode shall be selected on the circuit breaker according to the voltage level and short circuit current level.
In order to avoid such problems as thermal effect and electromagnetic effect when short circuit current occurs, it shall be noted that the installation position of the circuit breaker shall be as far away from the load center as possible; during the installation, it shall be ensured that the high voltage circuit breaker can be conveniently charged from the power distribution device, and the operating mechanism of the circuit breaker shall have enough space for movement; and the position of the operating mechanism of the circuit breaker shall be convenient to separate the working power supply from the working power supply.
Post time: Feb-15-2023