science C6 Electricity supply and wiring

Single phase wiring

• Low voltage

• Used in houses that need low voltage (less than 240V/10kW/50A)

Three-phase wiring

• High voltage

• Used in commercial and industrial areas (less than 415V/>10kW/>50A)

• Directly from substation

• The three-phase wiring which is more stable and reliable is used

Live wire

• Carry the alternating current at 240V from the substation to home.

Neutral wire

• Carry electrical current from home back to substation.

Main fuse

• Controls the amount of electricity supplied to home. Breaks the circuit automatically if excessive flow passes through it.

Electric meter

• Measures the amount of electricity used.

Main switch

• Controls the flow of electric current for all circuits in the house.

Circuit beakers (MCB, ELCB)

• Break the circuit when excess voltage flows through earth wire (short circuit)

Earth wire

• Carries leaked current to earth.

• Only has live wire and neutral wire

• Does not have fuse and earth wire

• Used for electrical appliances which requires electric current less than 2A

• Example: radio and electric clock.

3-pin plug

• Has 13A fuse that is connected to live wire

  Three pins:

• L- connected to live wire

• N- connected to neutral wire

• E- connected to earth wire

Safety Components in wiring system in homes fuse

• To protect wires and appliances from any excessive current flow.

• If the wire melts, the electricity supply will be cut off.

1. Cartridge fuse

• Wire cannot replace if brown.

• Usually used in 3-pin plug.

2. Replaceable wire fuse

• Wire can be replaced after brown.

• Used in main fuse box.

Determining the value of a fuse

• The value of a fuse ➡ the maximum value of current that can flow through the fuse without causing its fuse wire to melt.

• Common flow ratings ➡ 1A, 2A, 3A, 5A, 10A, 13A, and 30A.

• Choosing the value of a fuse ➡ depends on the value of the maximum current that flows through a circuit or electrical appliance.

• The fuse to be used should have a value which is slightly higher than the maximum current that flows through a circuit or electrical appliance in normal operating conditions.

• For example, an electric kettle that uses a maximum electric current of 11.34A should be installed with a 13A fuse.

Earth wire

• Another safety device in electrical wiring system.

• Has low resistance which connects appliances to the ground.

• If an electric leakage occurs, the current will low instead of passing through a person when touched (high resistance)