The difference between PT cabinet and metering cabinet in high voltage switchgear
Dec 23, 2020
High and low voltage switchgears are equipment for connecting high voltage or low voltage cables. Generally, power supply bureaus and substations use high voltage cabinets, which are then stepped down by transformers to low voltage cabinets, and low voltage cabinets to various power distribution boxes. It is nothing more than assembling some protective devices such as switches and circuit breakers into an integrated electrical device.
Normal use conditions of high voltage switchgear
1. Ambient temperature: the ambient air temperature does not exceed 40°C (upper limit), generally -5°C (lower limit), and -15°C in severe cold areas. If the ambient temperature is too high, the conductivity of the metal will decrease, the resistance will increase, and the surface oxidation will intensify. On the other hand, too high a temperature will greatly shorten the life of the insulation in the cabinet and reduce the insulation strength. On the contrary, if the ambient temperature is too low, internal stress will be generated in the insulating parts, which will eventually lead to the destruction of the insulating parts.
2. Altitude: generally no more than 1000 meters. For equipment installed at an altitude higher than 1000 meters, the insulation level of the external insulation should be the required insulation withstand voltage multiplied by the correction factor Ka [ka=1÷(1.1-H×10-4[x1])] Decided. Because the air is thin in high altitude areas, the external insulation of electrical appliances is easy to breakdown, so use reinforced insulation electrical appliances to increase the air insulation distance, or increase insulation protection measures in the switch cabinet.
3. Environmental humidity: The daily average value is not more than 95%, and the monthly average value is not more than 90%.
4. Earthquake intensity: no more than 8 degrees.
5. Other conditions: There is no place with fire, explosion, serious pollution, chemical corrosion and severe vibration.
The function of PT cabinet in high voltage switchgear:
1. Voltage measurement, providing the voltage circuit of the meter
2. It can provide operation and control power
3. Installation of overvoltage protector for each busbar
4. The needs of relay protection, such as bus insulation, overvoltage, undervoltage, automatic switching conditions, etc.
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 descends. Generally, after the cable enters into the incoming isolation cabinet, the busbar reaches the upper part of the cabinet, and then enters the line from the top to the bottom of the metering cabinet, from the bottom to the bottom of the incoming line (circuit breaker) cabinet, and finally to the upper part.
The difference between PT cabinet and metering cabinet in high voltage switchgear
1. The PT cabinet has a handcart. The metering cabinets are divided into regions, some areas do not have handcarts, and some places have handcarts. For example, Anhui Derun Electric KYN28 high voltage switch cabinet has a handcart.
2. The PT cabinet has a lightning arrester, which is placed in the handcart or behind the cabinet. The metering cabinet has no 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, but the PT does not.
5. The metering cabinet is generally used as a metering outlet cabinet or a metering contact cabinet. The PT cabinet is generally after the incoming line cabinet and in front of the feeder cabinet, only the main bus bar passes through, and the line is not used.
