High and low voltage distribution system

(1) Low voltage distribution system: Contemporary high-rise buildings adopt two independent 10kV power sources for simultaneous power supply. Normally, low voltage adopts single busbar segmentation, active switching, and mutual backup. The number of bus segments should be adapted to the number of power supply incoming circuits. Only when the power supply is one main and one backup, should we consider adopting a single busbar without segmented wiring. Almost all power supply incoming lines adopt cable incoming lines.

(2) The billing method adopts high supply and high calculation. But on the low voltage side, a design fee electricity meter is still installed, adopting a two-part electricity pricing method that separates lighting and energy. In some places, the power supply department has also included the electricity consumption of air conditioning equipment in the lighting pricing system. The usual practice is to install a total meter and energy meter, and subtract the energy meter from the total meter to obtain the lighting electricity fee for all.

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(3) To reduce the number of transformers, the capacity of a single transformer is usually chosen to be greater than 1000kVA. To limit the short-circuit current on the low voltage side, a connecting switch is installed in the center during the disconnection operation of the transformer in case of malfunction. Lighting and energy are separated from the installation of transformers. When the energy consumption capacity is too small, the energy transformer can remain in the installation and respond to energy load classification and billing on the low voltage side.

(4) The distribution methods for low-voltage systems and low-voltage branch lines basically adopt the jet system. The floor distribution system is a hybrid system. The important department in power distribution equipment is the branch line. The vertical shafts of contemporary high-rise buildings often adopt plug-in bus ducts. Due to the difficulty of routing, the degree branch line is often connected to the vertical shaft main branch line using full plastic cables. Each floor's vertical shaft is equipped with a floor to floor power distribution inquiry. The interlayer distribution box obtains power from the main branch line of the vertical shaft through the insertion of an active atmosphere switch. When there are many layers and a large load, it is common to divide the power supply according to the number of layers, or evacuate the transformers to the ground level, central level, or topmost level.

(5) All levels of switches in the low-voltage distribution system adopt active atmosphere switches (circuit breakers) and are equipped with three levels of overcurrent protection: braking, short delay, and long delay. The cover setting of active atmosphere switches at all levels should pay attention to selectivity and avoid tripping beyond the level.

(6) All elevators are requested to adopt a common cable incoming from two branch transformers. At the end distribution box of the elevator machine room, there is an active switching assembly of two power sources, which are mutually backup.

(7) The power factor should be compensated to 0.9-0.95 according to regulations. Reactive power compensation adopts the method of collective compensation. To reduce the capacity of transformers, they are often installed on the low voltage side and placed together with the distribution panel, but it is necessary to use phase-shifting capacitors.