electrical installation in buildings

7/27/2019 Electrical Installation in Buildings

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ELECTRICAL INSTALLATION IN BUILDINGS

Contents of this part is about

a) Current supply for domestic buildingsb) Electricity distribution in buildingsc) Components of electrical equipments

Introduction

Electricity Supply Specifications

Electricity supply for domestic consumers, according to MS IEC 60038 standards, meets the

following specifications: -

i. Single phase supply with nominal voltage of 230V, range +10%, -6%;ii. Three phase supply with nominal voltage of 400V, range +10%, -6%;

iii. Permitted frequency is 50Hz + 1%;Malaysia's BS 1363 Domestic AC power plug

Electricity transformer/convertor for US appliances.

These are the recommended wall outlet plug adapters for Malaysia.


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Electrical Generation and Distribution

I. Three phase supply Refers to alternating current that continually varies in both magnitude and

direction

Its consist of three overlapping currents, in one in each phase When 3 coils are rotated at a uniform speed in the magnetic field of an

alternator, 3 identical waveforms are obtained.

3 PHASE SUPPLY SYSTEM


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II.

One phase / single phase circuit In this circuit, the electromotive force (emf) undergoes one complete cycle of

variation when the conductors in the alternator rotate through the opposite

magnetic field set up by magnets.

The voltage rises to a maximum positive value then falling to zero before continuingto a maximum negative value, before returning to zero.

SINGLE PHASE SUPPLY


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The Planning Flow Chart for Single Phase and Three Phase Supply Building Wiring

System


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Features of Electrical Wiring

Composes of electrical wiring equipment such as cables, switch boards, main switches,

miniature circuit breakers (MCB) of fuses, residual current devices, etc

Example of Single phase consumer wiring


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Example of Three phase electrical wiring


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Example of Lighting Circuits Schematics Wiring

Single light point controlled by a one way switch

Two light points controlled by a one way switch

Two light points controlled separately by two one way switches


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Single light point controlled by a two way switch

Three light points controlled by two way switches and intermediate switch

Single flourescent light point controlled by a one way switch


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Example of socket outlet schematic wiring

Socket outletsingle socket

Socket outletsradial connection

Sockets outletsring circuit connection


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Distribution Of Electricity In Building final stage in the delivery of electricity to end users. A distribution

system's network carries electricity from the transmission system and delivers it to

consumers.

The modern distribution system begins as the primary circuit leaves the sub-stationand ends as the secondary service enters the customer's meter socket. A variety of

methods, materials, and equipment are used among the various utility companies, but

the end result is similar.

I. CONSUMER CONTROL UNIT Domestic installations have a consumer unit. Unit - in various sizes but in general they consist of an 80A microgap switch, with up

to 12 single-phase and neutral (SPN) fuses and neutral terminals.

The number of circuit provided will depend on the nature of the building.

II.

FUSES Is a device for opening a circuit by means of a conductor designed to melt when an

excessive current flows.

Purposeis to protect the cable and appliance from excess current flows, which mayoccur from a fault or result from the installation of a device having a higher current

rating than the fuses.
http://en.wikipedia.org/wiki/Power_deliveryhttp://en.wikipedia.org/wiki/Power_delivery


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Selection of Wiring Cable Type

The selection of the cable size has to take into consideration of these following features

All wiring cables must be PVC or PVC/PVC insulated with copper conductors.Conductors with cross sectional areas of 16mm2 or less must be of copper.

Aluminium conductors are not permitted.

Cables for swimming pools must be water resistant PE (polyethylene) insulated; The selected cable must be capable of delivering the electrical energy efficiently; The cable size allows it to carry the current without heating the cable; The voltage drop must not exceed 4% of the supply voltagevi. The cable insulation must be suitable for the surrounding conditions of the installation,

such as the ability to withstand the surrounding temperatures and the ability to provide

mechanical protection.

Each conductor in the installation must be protected from overcurrent by means ofovercurrent protection devices needed to prevent damage to the cable insulation.

5.2 Factors Related to Cable Current Carrying Capacity

The following factors in relation to the current carrying capacity of cables must be taken into

consideration;

Surface wiring using clipsgroup factor; Wiring using conduitsspace factor 40%; Wiring using ductsspace factor 45%; Concealed wiringgroup factor; and Concealed wiring using ductssurrounding temperature factor.

The correct installation for any installation depends on :-

The current to be carried The voltage drop The operating temperature


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For a given current, the greater conductor cross-sectional area, the less heat is generated.

Excessive heat will damage the insulation. If several cable are run in one conduit, duct or trunking, a temperature increase due to

bunching will occur.

To limit this effect, the cable size may have to be increased and the number of cablesrestricted to a certain percentage of the cross-sectional area of the conduit.

An insulatoris a material that offers a high resistance to the flow of electricity in alldirections.

PVC cable Mineral-insulated cable

PVC cable is :- Is widely used for domestic and commercial applications. Is largely unaffected by oil and many chemicals (non-hygroscopic, tough,

durable and chemically inert and will not support combustion.

electrical installation in buildings

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