Electric Encyclopedia: Design of High and Low Voltage Power Distribution System

(1) high-voltage power distribution system: modern high-rise buildings are using two independent 10kV power supply. General high-pressure single-bus segment, automatic switching, mutual backup. The number of bus segments, and the power line into the line to adapt. Only when the power supply is a master and a backup, only consider the use of single-bus non-segmented junction. Almost all of the power into the line using cable into the line.

(2) billing methods, the use of high for the meter. However, on the low-voltage side, there is still a design fee meter, which adopts two price methods that separate the lighting from the power. In some places, the electricity supply department again uses the electricity of the air-conditioning equipment and draws the entire lighting system. The general practice is to install the total meter and the dynamic meter, and subtract the dynamic meter from the total meter, all of which are used for lighting electricity bills.

(3) In order to reduce the number of transformers, the capacity of a single transformer is generally greater than 1000kVA. In order to limit the short-circuit current on the low-voltage side, the transformer should be disconnected during normal operation, and the contact switch should be set in the middle. Lighting and power set up separately from the transformer, when the power capacity is too small, the power transformer can be installed separately, and in the low-voltage side should be classified dynamic load classification.

(4) The distribution system of high-voltage system and low-voltage trunk basically uses radiating system. Floor distribution is a hybrid system. The main part of the distribution equipment is the trunk. Shafts of modern high-rise multi-use busbar slot. Due to the difficulty of the horizontal trunk line, the use of all-plastic cable and shaft mains connection. Each floor of the shaft set to ask a small distribution layer asked. Inter-floor distribution box by plug automatic air switch to obtain power from the shaft mains. When the number of floors is large, the load is usually divided by layers or the transformers are distributed on the ground floor, middle floor or top floor.

(5) Low-voltage power distribution system All levels of switches are used automatic air switch (circuit breaker), set the instantaneous, short delay, long delay three over-current protection device. Automatic air switch at all levels of protection setting, should pay attention to selective cooperation, to prevent the more grade trip.

(6) All elevators require the use of two different special transformer cable leads into the line. In the end of the elevator room distribution box, set up two automatic switching power supply, each standby.

(7) The power factor should be compensated to 0.9-0.95 according to regulations. Reactive power compensation using centralized compensation. In order to reduce the capacity of the transformer, it is mainly installed on the low-voltage side and put together with the distribution panel, but must adopt the phase-shift capacitor.