Switching device is an important transmission and distribution equipment, which is the power system (power generation, power transmission, transformation, supply, distribution, and other aspects of electricity) the electric drive system and control and protection equipment, all energy production Switching appliances are used in places where transmission, conversion, supply, distribution and use are used. As a staff member in the electric power industry, it is necessary to understand the common functions of switchgear. Let's go into the theme with Xiaobian , and the old driver can skip it!
The main function of the switchgear is to turn the circuit on and off, that is, to "open" and "off " the circuit , which is also the origin of the name of the switch. Specifically, it has the following four main functions:
(1) Control function
According to the operation requirements of the power grid or other power circuit, a certain part of the equipment or line is put into or out of operation, that is, under normal load current conditions, the circuit is turned on or off. This function is called control. This requires the switchgear to have a certain on-off capability, which can be operated with load and can reliably extinguish the arc generated when the load current is turned on and off .
Switching devices such as circuit breakers, load switches, and contactors all have control functions.
(2) Protection function
When the power line or electrical equipment fails, the faulty part is quickly removed from the power grid to ensure the normal operation of the fault-free part of the power grid . This effect is called protection. The fault current generated by the short circuit of the power grid is very large (can reach several times, ten times or even several times of the normal load current), and the damage is very serious and must be quickly removed. This requires the switching device to operate quickly and with sufficient on-off capability.
The switching device with protection function includes a circuit breaker, a fuse, a load switch and the like.
(3) Isolation function
After the power lines and equipment that are out of operation or need to be repaired are removed from the power grid (disconnected from the power supply), they must be reliably isolated from the power supply to form an obvious break with the power supply to prevent misoperation and overvoltage conditions. The power is turned on to ensure the safety of the equipment and maintenance personnel. This effect is called isolation. Electrical switch having a function of this circuit is only switched on or off a current at no-load or low current case, since without special quenching apparatus. But it requires a sufficient distance between the contacts and the insulation reliability at the time of disconnection, to ensure that bad weather and environmental conditions can be reliably isolated from the role, and to ensure that in case of flashover between the over-voltage and phase Does not cause breakdown of insulation.
The switching device with isolation function includes a high voltage isolation switch and a low pressure knife switch.
(4) Grounding function
Before the power line and power equipment are inspected, in addition to disconnecting the power supply and isolating the power supply, the three-phase short -circuit grounding is also required. The first function is to discharge the residual electric charge on the power line and the power equipment to the ground; Lines and power equipment and ground to maintain a zero point, in case a sudden call to cause a personal safety accident. This method can adopt a temporary hook ground line, but more convenient method is to use a ground switch.
Existing separate grounding switch structure, but also structure the combined disconnector, referred to isolated ground switch (rotary disconnector); there is a class three-position (ON, isolated, ground) Load switch .
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