Factories, Large Commercial Buildings Distribution Boards

Factories, Large Commercial Buildings Distribution Boards Points : factories, large commercial buildings distribution boards A three phase supply will be taken into large installations. Depending on the size it will, either be at 11 kV in the form of underground cable, or at medium voltage from overhead lines.

If the supply is at 11 kV, transformation in 440 volts is necessary and this will usually mean a sub-station on site. The point of entry of the incoming cable determines to a large extent the position of the transformers, and this to some degree determines the position of the buildings on the premises, as it can be expensive to run lengths of power cable to remote buildings.

Generally with factories a single tariff is charged, as the lighting is guaranteed to be under a certain percentage of the electricity consumed. In this case the Supply Company would install meters at the main input point indicating probably. kWh and kVarh. From these meters, the power would go to the main switchfuse or circuit near the mainswitches. In large installations, this is adopted for economic reasons since it cuts the cost of circuit cables. However, the cost of the lengths of these sub-circuit cables must be balanced against the length of the sub-main cable feeding the distribution fuse board.

Thus a 50ft. run of 71.05 2 twin core cable for a sub-circuit wing. Depending on the installation and type. and position of loading involved, distribution fuse boards can be fed by a form of ring main as shown in Fig.9. The deciding factors for locating distribution boards in a large installation are cost of cables, availability of suitable walls or supports for the board, the ease with which cables can be run to it, accessibility for replacement of fuses when installed, and freedom from dampness and fumes.