Building Services : Electrical System

PRINCIPLES OF ELECTRICITY

Electricity is using atomic theory as a basic. In this theory, there is an atom which is made up of protons, neutrons and electrons that having positive charge, neutral and negative charge respectively. Proton and neutron will surround by the electrons.

Electron flow

It flow from negative terminal to positive terminal of power supply through electrical circuit. When the atom from positive and negative side connected together on a conductive circuit which is a path that allow electrons to pass through.

Current flow

There are 2 forms of electricity which is static and current electricity.

Static electricity is an imbalance of electric charges within or on the surface of a material such as a movement or action to generate energy.

Current electricity which is come from a power source such as generator or battery.

Electricity

An electricity occurs is when an electricity circuit have voltage supply, conductor and load.

Circuit

Circuit have categories into 3 types which is series, parallel and combination of the both series and parallel.

Series is connected along a single path. Current is same in each of the components, and the voltage across the circuit is the sum of the voltages that across in each component.

Parallel is one of the circuit connected completely in parallel or more than 1 path.

There are types of condition that can happen in a circuit:

· Open circuit is no any current that are flow in the circuit.

· Closed circuit is a circuit that current is flowing.

· Shorted circuit is occurs when a voltage source has a low resistance path to ground. It will cause a large current flow and the wires get overheat.

Terminology

1. Current

Ø flow of electrons along a conductor

Ø Unit of the current is Ampere (A)

Ø Symbol: I

2. Voltage

Ø Describe electrical pressure or electromotive force (EMF) which used to force electrons to flow from the negative to positive terminal

Ø Unit: volt

Ø Symbol: V

3. Resistance

Ø Provide resistance to current flow also describe opposition to current flow.

Ø unit: ohm

Ø symbol: Ω

OHM’S LAW

where V = Voltage (V)

I = Current (A)

R = Resistance (Ω)

Ohm’s law states

“Current flow in circuit is directly proportional to the voltage across the circuit and inversely proportional to the resistance contained in the circuit, providing circuit conditions remain the same”

Ohm's law are used to solve simple circuit problems. Based on this law, resistance are held constant. Components that obey Ohm's Law are called 'ohmic' or 'linear' such as iron meanwhile silicon,LED, diode which does not obey Ohm's Law are called 'non-ohmic' or 'non-linear'.

Voltage is directly proportional when resistance is constant

Resistance is directly proportional with voltage when current is constant

Current is inversely proportional with resistance when voltage is constant

Power Generation

Actually, in power generation, one form of energy gets converted into electrical energy.

We produce electrical energy from various natural sources. The concept of power

generation is not always about hydro, nuclear plant etc, it is the emf.

There are six sources of electromotive force (voltage) :-

- Chemical - Pressure

- Light - Heat

- Magnetism - Friction

Chemical
A battery uses a chemical affect to produce electromotive force. As example is the
placement of a copper and zinc electrode together in a solution of sulphuric acid. The two metals reacts as the create a voltage potential.

Light

The sun’s rays can be used to produce a voltage potential. This action is achieved by using solar system. It is a best alternative source for power generation with low maintenance cost. A environment-friendly system and an ideal source for remote locations

Magnetism

The most common way of creating an electromotive force is by using magnetism. When a conductor passes through a magnetic field, cutting through the invisible lines of flux, a voltage is induced into the conductor. This method of creating electromotive force is used in:

- Wind generators - Tidal Generation - Hydro plants

Additional

Pressure

There's no energy involved in pressure alone. High school physics tells you that Work Done is Force x Distance. If your force never moves any distance, then it does no work, and so there's no energy transfer.

Heat (thermoelectric)
Thermoelectric devices are made from materials that can convert a temperature difference into electricity, without requiring any moving parts. thermoelectric generators take a temperature difference and turn it into electrical power. Amazingly, these materials can also be run in reverse!

Friction

By rubbing (friction) you can create charges which are responsible for generating electricity. If you can rub a very large number of particles, you may even be able to see a small spark. Thats what creates lightning.

System Involved

· transmission system

- Carries the power from the generating centres to the load centres

- Disseminate of electrical energy from power plant to high-voltage station

· distribution system

- Feeds the power to nearby homes and industries.

- Disturb electrical energy from high-voltage station to consumer fit-out source

Distribution Board (also known as panelboard, breaker panel, or electric panel)

A distribution board is a component of an electricity supply system that divides an electrical power feed into subsidiary circuits, while providing a protective fuse or circuit breaker for each circuit in a common enclosure.

It divides into two parts: - supply part

- consumer part

Supply Part

· Service Fuse

- Protect against excessive current and limiting consumer current

· KWH Meter

- Record power usage and charge

Consumer Part

· Interface between utility company and consumer wiring

· Location for main switch and protective devices for consumer wiring circuit

· Consists of three main devices

- Main switch

- RCCB (Residual Current Circuit Breaker)

- MCB (Miniature Circuit Breaker)

Final Sub-Circuits

1. Lighting Circuit 2. Power Circuit

💥 Circuits that directly connected 💪 Circuits connected to provide

to loads and use switch as control eletrical energy to portable

devices. eletrical devices through 13 A

and 15 A devices.

SINGLE PHASE

Single phase is a system, circuit or
device generating using a single
alternating voltage. All the voltage or
power are generated vary in
unison.Single phase also rotating a
single turn coil through a magnetic field.

THREE PHASE

Three phase is a system that carry three

phase supply. Its a fourth conductors

that called the neutral, connected

through protective device to earth. Usually connected using star connection and delta connection.

SINGLE PHASE VS THREE PHASE

Wires that used in single phase : Wires that used in three phase :

1. live conductor (yellow) 1. Red

2. neutral conductor (blue) 2. Blue

3. Earth Conductor (green) 3. Yellow

Source : google images


Source : google images

Other difference between single phase and three phase.

1. Single phase has 100 amp fuse meanwhile three phase has three 100 amp fuse.
2. Single phase is smaller than three phase.

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