Choice of Cables Distribution Boards

Choice of Cables Distribution Boards Points : choice of cables distribution boards, basic information on cables distribution boards Choice of Cables There is not much sense in planning a perfect installation on paper and then spoiling it all in practice by installing cheap low quality cables. Within a few months of installing inferior cables, consumers nearly always experience trouble with cables burning out, insulation breaking down, fuses blowing inexplicably, danger of shock whole installation has to be done. In other words, cheap cable is not so cheap after all.

Design Details about Estimating the Load Distribution Boards

Design Details about Estimating the Load Distribution Boards Points : Design Details about Estimating the Load Distribution Boards, Size of Switchgear, Size of Cable, Fuse Ratings, Solid Neutral Links, Colour Coding In order to find out the required ratings of main and sub main cables, fuses and switchgear in an installation, an estimate of the likely load should be made. This should be done by making a schedule of lamps, fixed apparatus, socket outlets etc, which are to be installed. From this schedule it will possible to calculate the total load and from that estimate the ratings of cable, fuses and switchgear. In some cases, the total load will be used all the time, but in other cases only 50% of the total possible load might be in use at any one time. i.e. a domestic consumer would be very unlikely to switch on all his lighting, cooking, radio, gramophones air-conditioning, electric irons, fans etc. etc. at any one time. Thus a load that adds up to 100 amps on paper might never exceed 70 amps in practice.

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.

Large Houses, Block of Flats, Offices Distribution Boards

Large Houses, Block of Flats, Offices Distribution Boards Points : large houses, block of flats, offices distribution boards Generally a three phase supply is taken into large houses or blocks of flats. The basic layout will be the same as with a single phase layout, except that with a block of flats there will be a light phase layout, except that with a block of flats there will be a light and power meter for each apartment. Since the three phase supply is 440 volt, special precautions must be taken to prevent shock at medium voltage.

If one lighting distribution fuse board is fed from the Red phase of a 4-wire 440/250 volt a.c. supply, and another is fed from the Blue phase, then if they were near together it might be possible to receive a 440 volt shock if the terminals of both were touched simultaneously. In the same way it is also possible to receive a medium voltage shock at any three phase distribution board or switchgear.

Houses and Small Installations Distribution Boards

Houses and Small Installations Distribution Boards Points : houses and small installations distribution boards If a house or small installation does not contain relatively high current consuming appliances, such as electric cookers, air-conditioners etc., only a single phase supply will be brought in. Usually, in this case, the lighting and power will be metered separately, so separate main switches are required leading to main lighting and power distribution boards.

The location of the meters and control gear in a house is seldom done with any regard to safety. Switchfuses are installed haphazardly around a house at any height on a wall.

Term Use in Electrical Distribution System

Term Use in Electrical Distribution System Points : term use in electrical distribution system Points The termination of fixed wiring feeding a lighting fitting, socket outlet or any other current consuming appliance is called a Point. Main Cable Main Cables are classed as those leading tip to combination switchfuse hoards, or in the case of smaller installations, up to the main distribution fuse board.

Distribution Fuse-Board

Distribution Fuse-Board Points : distribution fuse-board This is a metal or hardwood case containing two or more fuses (or other overload protective devices). Distribution fuse boards must be connected to and controlled by the main switchgear. or a separate way on a large distribution fuse board.

Switchfuse

Switchfuse Points : switchfuse, definition Every installation of whatever size must be controlled by one or more main switches. The main switchgear may consist of a separate switch and fuses, a combined switchfuse, or a circuit breaker. The design of switchfuseas varies according to the size but most of the larger types have a metal casing. Usually in small or domestic installations the fuses are rewire able, but in large commercial or industrial installations H.R.C. fuses are used.