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BUILDING SERVICES 2Electricity

What is Electricity?Electricity is generated from the motion of tiny charged atomic particles called electrons and protons!

Protons = +Electrons = -

Sources of Electricity

ThermalSolarNuclearGeothermalHydroelectricWindHow do we get electricity?Energy from one of the sources is converted by machines at the power plant to Electricity and then put onto the Electric Power Grid

Electric Power GridPower PlantsTransmission LinesSubstationsPower LinesTransformersElectrical Wiring and Circuit Box

4The Power GridThis slide helps connect how we use the energy from one of the previously mentioned sources to power things in our home. It is done by way of the electric power grid. This grid starts after the energy from a source has been converted by machines into usable electricity. Now, the electricity must follow a path to get to our homes. This path is known as the power grid and has many parts which fulfill a specific function. Power Source

Wiring or Conductors (insulated side and ground)

Control Device (switch)

Load

Circuit Protection (fuse)

Circuit Symbols5

Think of what has to happen to turn on a light6

Alternator provides power for running vehicle

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Alternator provides power for running vehicle

8Assignment 1 : Schematic Electrical layout of your residenceCurrent is the rate at which electric charge flows past a point in a circuit.

Voltage is the electrical force that would drive an electric current between two points. Current and voltageLaws of Electrical circuitsOhms LawKirchhoffs lawOhms LawThe current flowing in a conductor is Directly proportional to the applied voltage V and Inversely proportional to its resistance R

I = V/RKirchhoffs lawKirchhoffs current lawKirchhoffs Voltage LawKirchhoffs current lawAt any instant the algebraic sum of the currents flowing into any junction in a circuit is zero

For example I1 I2 I3 = 0 I2 = I1 I3 = 10 3 = 7 A

Kirchhoffs Voltage LawAt any instant the algebraic sum of the voltages around any loop in a circuit is Zero

For example E V1 V2 = 0 V1 = E V2 = 12 7 = 5 V

Electrical ServiceElectrical services are available in Single-phase current or Three-phase current (poly-phase). Single Phase CurrentWith single-phase current, the voltage rises to a peak in one direction of flow, subsides to zero, reverses, rises to a peak in the opposite direction, subsides to zero, and so on.

The cycle repeats itself 60 times every second, which is where we get the term 60-cycle or 60-hertz alternating current.

Single-phase current requires the use of one transformer.

In the case of three-phase current, the same pattern exists, except that there are three separate and distinct single-phase currents, which are combined so they can be transmitted over three or four wires.

The three currents rise to a peak in one direction, subside, reverse, and so on; however they do not peak at the same time.

Each phase reaches its peak 120 degrees apart from the others.

Three-phase current requires two or three transformers. Three-Phase Current

What is Earthing? The process of connecting metallic bodies of all the electrical apparatus and equipment to huge mass of earth by a wire having negligible resistance is called Earthing.The term earthing means connecting the neutral point of supply system or the non current carrying parts of the electrical apparatus to the general mass of earth in such a manner that all times an immediate discharge of electrical energy takes place without danger.

Concept of Earthing SystemsAll the people living or working in residential, commercial and industrial installations, particularly the operators and personnel who are in close operation and contact with electrical systems and machineries, should essentially be protected against possible electrification. To achieve this protection, earthing system of an installation is defined, designed and installed according to the standard requirements..Good Earthing Means

Good Earthing must have low impedance enough to ensure that sufficient currentcan flow through the safety device so thatit disconnects the supply (