Distribution of Electricity in Multi-Storey Building

Distribution of Electricity in Multi-Storey Building

When electricity is required to be distributed in one or more than one storey building, in this situation mostly a separate energy meter is installed on the ground floor for each floor. The supply wires from every energy meter are ejected and carried to the distribution fuse board of every floor passing through the main switch and main fuse on the floor. The sub-circuits are drawn from the distribution boards according to requirements. Then, a connection of the sub-circuits is made with the sub-distribution boards or switchboard, wherefrom final sub-circuits or branch circuits are drawn for lamps, fans, sockets, etc. This is a fine, balanced, and decent system for the distribution of electricity within a multi-story building, owing to which, the beautification of the premises enhances.  

However, if the distribution of electricity in a multi-story building is required to be carried out through a single energy meter installed on the ground floor, first wires are drawn from the energy meter and carried to the main switch and main distribution fuse board. The distribution fuse board is generally installed on the lowest floor, so that quick access to it may be possible in the case of an accident. Then, separate sub-circuits are ejected from this distribution fuse board for every floor, which is connected to the distribution board existing on every floor. This has been illustrated in figure 5.4.

Distribution of Electricity

Then, final sub-circuits or branch circuits are drawn and carried to the lamps, fans, sockets, etc., existing on the floor. This method for the distribution of electricity is also a very perfect and balanced one, and the attractiveness of the premises does not suffer as a result of adopting this particular procedure. However, the method of installing a separate energy meter on every floor is generally preferred over the system of supplying electricity to all the floors (maximum 5 or 6) through a single energy meter. 

Remember that fuses of such a rating are always installed on a main distribution fuse board, which can pass the total current of all the distribution boards from within it, whereas in every distribution board, only such a rating fuse is installed, which is according to the load (e.g., fans, lamps, etc.) connected to it. Moreover, in a situation of making a supply to all the stories of a building from a single energy meter, the wiring of every floor should be divided into at least three circuits. The object behind distribution into three circuits instead of one tends to be that;

(i). If the fuse of a sub-distribution board melts as a result of some fault (short circuit or open circuit), then all lamps on this floor do not turn OFF, and only the concerned circuit be closed and light on the rest of the floor remains restored.  

(ii). If the wiring of every story consists of just one circuit instead of three, then in a situation of a load increase, excess current will pass through this wire owing to a load increase, as a result, it will get heated. As a result of extreme heating of wires, not only a danger of melting down of insulation of wires prevails but there also persists a danger of breaking out of a fire in the building apart from the wiring damage. Furthermore, bulbs, tubes, and electric appliances won’t be able to receive a full voltage owing to a voltage drop increase as a result of an increase in the wires’ resistance, as a result of which, their performance suffers. 

Distribution of Electricity

Distribution of Light and Power Circuits in a Flat

If in any residential building or flat, the number of appliances working on electricity is low, a single-phase supply is provided in such places. Lighting and power circuits are made separately. Further, lighting and power distribution boards are controlled through separate main switches. In figure 5.5, a similar layout for the distribution of electricity has been illustrated. Remember that the supply company has nowadays abolished sealed fuse and neutral link. Now, the electric company supplies power directly to the lights and separate energy meters installed within a consumer’s premises from the nearest pole. This has been illustrated in figure 5.6.

Figure 5.6 – Distribution of electricity in a 4-story building

Distribution of Electricity

When a supply company (WAPDA etc.) provides an electricity service line within the precincts of a consumer, then according to the figure, first a sealed fuse and a neutral link of the supply company is being installed after the cable ceiling box. After this, separate meters and meter fuses are installed for power and light according to one’s needs. Then supply transmits to the consumer’s main power and main light switches from the supply company’s light and power meters and meter fuses, from where it transmits on the corresponding distribution fuse boards (D.F.B). Fuses are installed inside the distribution fuse boards, through which this supply is carried to the final sub-circuit. Remember that the final sub-circuit is the final circuit of any electrical system, which supplies electricity to load. 

The meters and other electrical equipment fitted in small installations (i.e., houses or flats) for controlling supply must always be installed at some secure places in the house. They must always be enclosed in any specific iron or wood made cabinets and installed at a reasonable height, so that children cannot reach them. The alphabet “L” should be written on all the distribution fuse boards, whereas “P” must be written on all power circuit distribution fuse boards. Moreover, a capacity from 10 to 20 percent must be retained in a distribution fuse board to accommodate any addition expected in the future. 

Distribution of Light and Power Circuits to Four Flats

In figure 5.7, two alternative layouts for the distribution of electricity to flats have been illustrated. According to the method shown in first the layout, a three-phase supply has been provided to the main switch or circuit breaker via meter and meter fuse. The total load has equally been divided within these three phases. A single-phase supply is being made by means of taking a phase and a neutral from three-phase. This single-phase supply has been divided into two circuits (i.e., light circuit and power circuit), and separate meters, as well as the main switches, have been installed within each flat of a large building. 

In order to provide supply to the flats, an alternative method can also be used, which has been illustrated in the following figure. According to the alternative method, the three-phase supply has been divided into two three-phase branches of light and power, and separate meters and main switches have been installed within each branch. Now, separate single-phase light and power supply have been provided on every flat from the main light switch and main power switch via light and power switch fuses.

As a better precaution, all three-phase equipment or appliances should be installed in a locked room. A small locked room constructed on way to the servant quarters in large flats tends to be a more suitable place. Whereas, equipment is generally installed in the basement of a flat’s blocks or a commercial building. In all such installations, re-wire-able fuses are generally used because they are less costly, and replacing them is easy. However, miniature circuit breakers are also now used instead of a fuse. Remember that under this type of installation, more than one phase should never be carried from a single apartment or a flat, and it is more feasible to install entire circuit breakers or distribution boards in a control room located near the main switch. 

Utilization Factor or Coefficient of Utilization

We know that the entire light being emitted through a bulb is not available on the working plane. The ratio between luminous flux, and total luminous flux provided by the source supply, is called the utilization factor or the coefficient of utilization, or the ratio between the used luminous levels and the emitted lumens, is called the utilization factor. Thus,

Utilization factor = Lumens actually received on a working plane/ Lumens emitted by the light source

Figure 5.7 – Two alternative layouts of distribution to flats

Distribution of Electricity

Distribution of Electricity

The value of this factor keeps changing, and it depends on the following points;

(i). on the type of lighting system, whether it is direct or indirect one

(ii). On the type of fitting, and on the height of the place where it is being installed

(iii). On the surface of roofs and walls and their colors

(iv). To some extent, on the size and shape of a room

For example, its value keeps changing for direct lighting between 0.4, and 0.6. It depends particularly on the shape of a room, type, and height of a fitting. However, its dependence on the color of walls and roofs is very less. Its value for the indirect lighting tends to be between 0.1, and 0.35, however, in such a situation, the impact of roofs and walls, wherefrom light reflects on the working plane, is substantially large.

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My name is Shahzada Fahad and I am an Electrical Engineer. I have been doing Job in UAE as a site engineer in an Electrical Construction Company. Currently, I am running my own YouTube channel "Electronic Clinic", and managing this Website. My Hobbies are * Watching Movies * Music * Martial Arts * Photography * Travelling * Make Sketches and so on...

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