High and low voltage switchgear, as its name suggests, is a device that connects high-voltage or low-voltage cables. Generally, power supply bureaus and substations use high-voltage cabinets, and then step down through transformers to low-voltage cabinets, and low-voltage cabinets to power distribution boxes. The whole thing is to assemble some protective devices such as switch breakers into one integrated electrical equipment.
1. Ambient temperature: The ambient air temperature does not exceed 40 °C (upper limit), the general area is -5 °C (lower limit), and the cold area can be -15 °C. When the ambient temperature is too high, the conductivity of the metal is reduced, the electrical resistance is increased, and the surface oxidation is intensified. On the other hand, the excessively high temperature also shortens the life of the insulating member in the cabinet and the insulation strength decreases. Conversely, if the ambient temperature is too low, internal stress will be generated in the insulating member, which will eventually lead to the destruction of the insulating member.
2, altitude: generally does not exceed 1000 meters. For equipment installed at altitudes above 1000 m, the insulation level of the outer insulation shall be multiplied by the required insulation withstand voltage Ka[ka=1÷(1.1-H×10-4[x1])] Decide. Due to the thin air in the high altitude area, the external insulation of the electrical appliance is easy to break down. Therefore, the reinforced insulated electric appliance is used to increase the air insulation distance, or the insulation protection measures are added in the switch cabinet.
3. Ambient humidity: The daily average is not more than 95%, and the monthly average is not more than 90%.
4. Earthquake intensity: no more than 8 degrees.
5. Other conditions: no fire, explosion hazard, serious pollution, chemical corrosion and severe vibration.
The role of the PT cabinet in the high voltage switchgear:
1, voltage measurement, provide the voltage circuit of the meter
2, can provide operation and control power
3. Installation of each busbar overvoltage protector
4. The need for relay protection, such as busbar insulation, overvoltage, undervoltage, and self-injection conditions.
The metering cabinet in the high voltage switchgear has two functions:
1. It is the measurement of electricity consumption. Generally, this metering cabinet is managed by the power department.
2. The busbar is lowered. After the cable enters the incoming line isolation cabinet, the busbar goes to the upper part of the cabinet, and then goes to the lower part of the metering cabinet from the upper part to the lower part, the lower part to the incoming line (breaker) cabinet, and finally to the upper part.
1. The PT cabinet has a handcart. The metering cabinets are divided into regions, some areas have no hand trucks, and some places have hand trucks. For example, Anhui Derun Electric KYN28 high voltage switchgear has a handcart.
2, PT cabinet has a lightning arrester, placed in the handcart or behind the cabinet. The metering cabinet does not have a lightning arrester.
3. The PT cabinet has no live display and the metering cabinet has a live display.
4, the metering cabinet has a current transformer, PT does not.
5. The metering cabinets are generally used as metering outlet cabinets or metering cabinets. The PT cabinet is generally behind the inlet cabinet and in front of the feeder cabinet. Only the main busbar passes through and no line is used.
1, the installation location is different
The switchgear cabinets are installed side by side in the room, mainly on the feeder line of the substation or the line terminal opening and closing.
Most of the ring network cabinets are installed on the roadsides on both sides of the outdoor street, and the opening and closing place is replaced at a place where there is no way to build a house.
2. The structure and function of the cabinet are different
The large functional structure of the switchgear is complex and often appears in the form of a combined structure. Moreover, the breaking structure of the switch cabinet is a circuit breaker, and the safety mechanism is a grounding line of the disconnecting switch and the grounding knife gate.
The ring network cabinet is small in size and simple in operation, and is mainly operated by a manually operated load switch. The cable connection is convenient, without the isolation switch. In the case of the switch opening, the grounding wire of the grounding knife gate can be closed.
3, the operation ticket and workflow are different
In the event of a line failure, the switchgear can trip itself according to the preset protection parameters, which can quickly break the line fault and protect the electrical equipment from further damage. It is also possible to manually operate the switchgear to open the power supply of the entire line.
The ring network cabinet adopts the structure of the load switch and the fuse barrel. When it encounters a large fault current, it will not trip by itself, and directly blows the fuse to stop the line supply. Manual splitting is only used in accordance with the provisions of the operating work ticket.
4. Different roles in distribution line management
The switchgear plays a rapid protection role in the management of the power distribution network power supply system. The setting of various protection parameters is a very important task. After the line operation mode and the line structure change, it is necessary to re-correct the protection parameters in time to prevent The switchgear has been rejected and malfunctioned.
The ring network cabinet mainly plays a role in adjusting the line structure and distributing the line load reasonably and evenly. Add spare lines in the key power supply area, and the ring network cabinet plays the role of hot backup of the line.
5, ring network cabinet and intelligent switch cabinet
The power load density in the central area of ​​the city is already high, and the power supply lines are complicated. How to improve the safety and reliability of the power supply is to increase the trunk line switch, set up multiple branches of the line, improve the network topology of the distribution network, and realize the power supply line. Networked structure layout.
Improve the operational flexibility of dispatch management of the distribution network. Under this new business demand, only the advanced electronic technology can be used to transform the ring network cabinet to improve the technical level of the switch cabinet. The modified intelligent switchgear can detect the real-time status of the distribution network, the switching operation status of the switchgear, the real-time current load of the line, and other grid information. At the same time, it can detect faults online, and locate faults and timely alarms. A series of actions is very important for power grid companies to improve the safety and reliability of power supply.
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