First, what is the load switch?
It is a control electrical apparatus with simple arc extinguishing device, which can have load division and closing circuit. Can break a certain load current and overload current, but can not break the short circuit current, must be used in series with the high voltage fuse, with the fuse to cut the short circuit current.
Function of load switch:
1, open and close cooperation. Because it has a certain arc extinguishing ability, it can be used to break and close the load current and a certain multiple (usually 3-4 times) of the overload current; It can also be used to open and close no-load transformers with larger capacity than the isolation switch, longer no-load lines, and sometimes used to open and close large-capacity capacitor banks.
2. Substitution. Load switch and current limiting fuse in series combination can be used instead of circuit breaker. That is, the overload current that is less than a certain multiple is borne by the load switch, and the overload current and short circuit current that is borne by the current limiting fuse.
3, the load switch and the current limiting fuse are combined in series into one load switch, which is called "load switch-fuse combination appliance" in the national standard. The fuse can be installed on the power side of the load switch or on the power side of the load switch. When it is not necessary to replace the fuse frequently, the former arrangement should be adopted in order to use the function of the load switch as an isolation switch to isolate the voltage applied to the current limiting fuse.
Two, what is the isolation switch?
It is a control appliance without arc extinguishing device, and its main function is to isolate the power supply to ensure the safety maintenance of other electrical equipment, so it is not allowed to operate with load. However, under certain conditions, the low-power circuit is allowed to be switched on or off. It is the most frequently used electrical device in the high voltage switch
The function of the isolation switch:
1. After opening, establish a reliable insulation gap, and separate the equipment or line that needs to be repaired from the power supply with an obvious disconnect point to ensure the safety of the maintenance personnel and equipment.
2, according to the operation needs, change the line.
3, it can be used to divide and close the small current in the line, such as the charging current of the bushing, bus, connection head, short cable, the capacitor current of the switching capacitor, the circulation of the double bus exchange and the excitation current of the voltage transformer.
4, according to the specific situation of different structure types, it can be used to divide and combine the no-load excitation current of a certain capacity transformer.
The high voltage isolation switch can be divided into outdoor high voltage isolation switch and indoor high voltage isolation switch according to the different installation methods.
Outdoor high pressure isolation switch refers to the high pressure isolation switch that can withstand wind, rain, snow, pollution, condensation, ice and thick frost, etc., suitable for installation on the terrace.
According to the different insulation pillar structure can be divided into single-column isolation switch, double-column isolation switch, three-column isolation switch. Among them, the single-column isolation switch directly uses the vertical space as the electrical insulation of the fracture under the overhead bus, so it has the obvious advantage of saving the floor area, reducing the lead wire, and the opening and closing state is particularly clear. In the case of UHV transmission, the effect of saving land area is more significant when the single column isolation switch is used in the substation.
Isolation switch in low-voltage equipment is mainly suitable for residential, building and other low-voltage terminal distribution system.
Main functions: load breaking and connecting lines.
Third, what is the vacuum circuit breaker?
Because the extinguishing medium and the insulating medium of the contact gap after the arc extinguishing are high vacuum; It has the advantages of small size, light weight, frequent operation and no maintenance, and is widely used in distribution network.
Vacuum circuit breaker is a 3-10kV, 50Hz three-phase AC system in the indoor distribution device, for industrial and mining enterprises, power plants, substations as electrical equipment protection and control, especially suitable for non-oil, less maintenance and frequent operation of the use of places. Circuit breakers can be configured in middle cabinets, double cabinets, and fixed cabinets to control and protect high-voltage electrical equipment.
1. Working principle of vacuum circuit breaker
When the dynamic and static contacts are opened under the action of the operating mechanism, an arc is generated between the contacts, and the surface of the contacts evaporates steam at high temperature. Due to the special shape of the contacts, a magnetic field is generated when the current passes through, and the arc moves rapidly along the tangential direction of the surface of the contacts under the action of this magnetic field, and part of the metal steam condenses on the metal cylinder (shielding cover). The arc is extinguished at the natural zero, and the strength of the medium between the contacts quickly recovers.
2, vacuum circuit breaker function
The circuit breaker has overload, short circuit and undervoltage protection functions, and has the ability to protect the line and power supply.
Four, the difference between load switch and isolation switch
The first difference is that they cut off different currents.
Because the isolation switch has no arc extinguishing device, it is only suitable for cutting off the no-load current, can not cut off the load current, short circuit current, so the isolation switch can only operate safely when the circuit is safely disconnected, and it is strictly operated with load, so as not to cause safety accidents. Because the load switch has an arc extinguishing device, it can overload current and rated load current, but the same can not cut off the short circuit current.
The second point is that the load switch has an arc extinguishing device, and the isolation switch does not have such a device.
So what difference does it make with or without this extinguishing device? The so-called arc extinguishing device is to be able to better help to disconnect and close the switching appliance, but also to effectively limit the arc and help the arc to extinguish. With such an arc extinguishing device, it is safer for switching appliances. So most of the switchgear inside is by the arc extinguishing device. Especially switches for home use.
Third, they work differently.
Because there is no arc extinguishing device, the isolation switch can only be applied to the high-voltage circuit device that needs to be live and the part that needs to be cut off for an isolation role, so as to ensure the maintenance and inspection of the high-voltage circuit and ensure the safety of the personnel. The load switch is applied to fixed high voltage equipment, which can cut off the fault current and rated current in high voltage equipment, so the role of the two is different, but both are applied to high voltage equipment.