science f3 c8-ppt-part iv electric supply and wiring system at home

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GENERATION OF ELECTRICITYScience Form 3 Chapter 8

Last update: 4/8/2010

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Part IV Electrical Supply and Wiring System at Home

F3 C8 GENERATION OF ELECTRICITY

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Electrical Supply to Our Home

• The electrical supply to our homes comes from the local substation

• The current is brought in by the live wire

• The current is returned to the substation by the neutral wire which is earthed at the substation

• The wiring system at home also has an earth wire

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Electrical Supply to Our Home

• Any current leaked from an electrical appliance while in use is transmitted to the earth by the earth wire

• The current supplied is an alternating current at a voltage of 220V-240V

• All the lamps and electrical appliances in the house are connected in parallel

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Wiring System at Home

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Main fuse box

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Main fuse box

• Maintains the main fuse connected on the live wire

• Excess current flowing into the house will cause it to melt and break the hourse circuit

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Electric Meter

Records the amount of electrical energy used. M’sia unit is called the kilowatt-hour (kWh)

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Main electric switch

• Main electrical switch on the live wire controls the current flowing into the house circuit

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Circuit breaker

• Trips automatically and breaks the house circuit when excess current flows through it– E.g. Lightning

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ELCB (Earth Leakage Circuit Breaker)

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Parts and Function of the Electrical Wiring System

Parts Functions

Main fuse Breaks the circuit if the current exceed a safe value

Main switch Disconnects the electrical power supply from the mains when electrical energy is not needed

Circuit breaker Cuts off the electric current flowing through a circui tunder abnormal conditions

Live wire Carries the electric current from the susbtation to the house

Neutral wire Carries the electric current from the house back to the substaion

Earth wire Connects an electrical appliance directly to the earth

Electric meter Measures the amount of electrical energy used

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2 Types of Wiring System

• Single-phase wiring system– Usually used in our homes

• Three-phase wiring system– Usually used in commercial and industrial areas

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Single-phase Switch

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Triple-phase Switch

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Single-phase distribution lines and three-phase distribution lines

• Electrical power is distributed on distribution lines.

• It is usually distribution from substations on three-phase distribution lines.

• This only requires single-phase distribution lines. It is a common practice to tap single-phase lines off a three-phase line

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Single-phase distribution lines and three-phase distribution lines

• The three-phased distribution lines run along major streets, and commercial and industrial areas. In these places, there is a need for high voltage, for example 415V.

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Three-phased Distribution Lines

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3-pin plug

• Each wire colour is based on the international colour code

• Live wire-brown• Neutral wire-blue• Earth wire-yellow

with green strips