earhting definition jiwinnie

8/23/2019 Earhting Definition Jiwinnie

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GROUP MEMBER:

LAWRENCE THIONGJIWINNIE CHLERA

HASDAH BINTI DARWIS

NORHASHINAH BINTI ZAINAL

NORHASLINDA ALBERT C.JARTHUR CHIN

DENNIS VILLEGAS


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2.1 UNDERSTAND RELATED MSIEC

60364 AND ELECTRICITYREGULATION


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2.1.1 EXPLAIN THE SPECIFICATION OFELECTRICAL SUPPLY SYSTEM


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List of energy sources for power generation

i. Sun (matahari)

ii. Wind (angin)

iii. Fuel (bahan api)

iv. Nuclear(Nuklear)

v. Renewable Energy (tenaga yang boleh diperbaharui)


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Types of power generation plants

i. Solar power plant

ii. Thermal power plant (using coal, oil and gas)

iii. Nuclear power plantiv. Hydro power plant

v. Turbin gas power plant


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i. Solar power plant


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ii. Thermal power plant (using coal, oil and gas)


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iii. Nuclear power plant


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v. Turbin gas power plant


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iv. Hydro power plant


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In electricity systems, an earthing system define as theelectrical potential of the conductors relative to the Earths

conductive surface. Earthing system can effect the safety, electromagnetic of

the power supply and regulation can vary considerablyamong countries.

Most electrical system connect one supply to theearth(ground) and this is well known as the EarthingSystem.

Definition of Earthing system

2.1.2 EXPLAIN EARTHING SYSTEM


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If a fault within an electrical device connects a "hot"(unearthed) supply conductor to an exposed conductivesurface, anyone touching it while electrically connected tothe earth ( for example : by standing on it, or touchingan earthed sink) will complete a circuit back to the earthedsupply conductor and receive an electric shock.


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TT system

IT system

TN-S system

TN-C-S system

TN-C system


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TT system

This system normally used for consumer power supply.

No earthing system provided by power distributor.

The owner must install the earthing protection by their own connection to

the earth.They must installing a suitable electrode and safe arrangement for

which they are responsibility to their installation.

The neutral and earthing conductor must be separately through

the installation because power distributor only provide the supply neutral or

protective conductor for the connection to consumer.

The advantage of this system is it clear from the noise of high or lowfrequency,not have risk of neutral broken or failure and suitable for special

application like telecommunication.

TT system is suitable for premises where all AC power circuits are residual

current device (RCD) protected.
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IT system

This system is similar with TT system but totally differentin earthing supply.

The distributor system not have any connection to earthor it have only a high impedance connection.

It mean the usual protection is not effective for thissystem.

This type is not for consumer power supply.

It special for power distributor such as substation or area.


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TN-S system

This system has the neutral of power supply withconnection of earth only at one point to the source.theconsumers earthing terminal is usually connected to themetallic Armour of the distributors cable into the HV / LV

transformer.

It is commonly used for underground power supply to thepremise or factory from the distributor substation tocustomer substation.

This earth terminal is connected by the supply protectiveconductor (PE) back to the star point (neutral) of the

secondary winding of the supply transformer, which is alsoconnected at that point to an earth electrode.


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TN-C-S system

This system has the supply neutral conductor of adistribution main connected with earth at source as

protective multiple earthing (PME).

The supply distributor neutral conductor is also used toreturn earth fault currents from the consumer installationback to the source with a safely manner.

The power supply distributor will provide a consumersearthing terminal which is linked to the incoming neutralconductor.

This combined earth and neutral system called theprotective and neutral conductor (PEN) or the combinedneutral and earth conductor (CNE).


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TN-C system

This system is not familiar or unusual for earthing system.Ita combined PEN conductor fulfills the functions of both a PEand an N conductor.

The PEN conductor is the sheath of a cable and therefore is

concentric with (totally surrounds) the phase conductor(s).

For wiring or cabling purpose,the suitable material is usesmineral insulated cable, the metallic copper sheath being thecombined neutral and earth conductor.

Normally this system used for ships or offshore platformearthing system.RCD protected is not function properly forthis system.


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TT EARTHING SYSTEM

The supply source has a direct connection to

earth. All exposed conductive parts of an

installation also are connected to an earth

electrode that is electrical independent of thesource earth.


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The Stucture Of TT Earthing

system


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Fault Behavior in the TT

Earthing System

When an insulation fault occurs, the fault

current Id is mainly limited by the earth

resistances (Ra and Rb).

At least one residual current device (RCD)must be fitted at the supply end of the

installation.

In order to increase availability of electrical

power, use of several RCDs en-sures time and

current discrimination on tripping [16].


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Advantages of the TT

Earthing System

The most commonly found earthing system.

Faults in the LV and MV grid do not migrate to

other customers in the LV grid.

Good security condition, as the potential rise ofthe grounded conductive part must be limited at

50 V for a fault inside the installation and at 0V

for a fault on the network.

Simple earthing of the installation and the

easiest to implement.

No influence of extending the network.


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Disadvantages of the TT

Earthing System

Each customer needs to install

and maintain its own ground electrode. Safetyand protection depends on the customer, thuscomplete reliability is not assured.

High over voltages may occur between all live

parts and between live parts and PE conductor. Possible overvoltage stress on equipment

insulation of the installation.


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Earthing of electrical systems is essential for the correct

functioning and the protecting of life and equipment in the

event of faults.

The earth electrode (connection of the earthing system to the

ground) is an essential part of any system.

The estimation of electrode resistance and functioning during

the design stage ensures workable solutions are proposed,

enhances the operation and potentially reduces the cost of any

installation.


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The earth electrode, where used, is the means of making contact with the

general mass of earth. Thus it must be tested to ensure that good contact is

made. A major consideration here is to ensure that the electrode resistance is notso high that the voltage from earthed metal work to earth exceeds 50 V. Where

an RCD is used, this means that the result of multiplying the RCD operating

current (in amperes) by the electrode resistance (in ohms) does not exceed 50

(volts). for normal dry locations, or 25 (volts) for construction sites and

agricultural premises.


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To ensure that the resistance of the test leads does not affect the result, separate

leads should be used for these connections.

If the test lead resistance is negligible, terminals C1 and P1 may be bridged at the

instrument and connected to the earth electrode with a single lead.

Terminals C2 and P2 are connected to temporary spikes which are driven into the

ground, making a straight line with the electrode under test.

It is important that the test spikes are far enough from each other and from the

electrode under test.

The tester provides an alternating output to prevent electrolytic effects. If the

resistance to earth of the temporary spikes Y and Z is too high, a reduction is likely if

they are driven deeper or if they are watered.


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The system can be adjusted by variation of the resistor R, is passed through the

electrode under test (X) to the general mass of earth and hence to the test

electrode Y.

The voltmeter connected from X to Z measures the volt drop from X to the general

mass of earth. The electrode resistance is calculated from:

Voltmeter reading (V)

Ammeter reading (A)

As in the case of the dedicated tester, the test electrode Z must again be moved

and extra readings taken to ensure that resistance areas do not overlap.

It is important that the voltmeter used has high resistance (at least 200 Ohms /V) or

its low resistance in parallel with that of the electrode under test will give a false

result.


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The tester is connected between the phase at the origin of the installation and the earth

electrode under test.

The test is then carried out, the result being taken as the electrode resistance although

the resistance of the protective system from the origin of the installation to the furthest

paint of the installation must be added to it before its use to verify that the 50 V level is

not exceeded.

If an RCD with a low operating current is used, the protective system resistance is likely

to be negligible by comparison with the permissible electrode resistance.


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The resistance of the electrode or earth interface rarely remains constant

Among the principal factors affecting this resistance are the following:

Humidity of the soil

The seasonal changes in the moisture content of the soil can be significant at depths

of up to 2 meters.

At a depth of 1 metre the resistivity and therefore the resistance can vary by a ratio of

1 to 3 between a wet winter and a dry summer in temperate regions

Frost

Frozen earth can increase the resistivity of the soil by several orders of magnitude.

This is one reason for recommending the installation of deep electrodes, in particular

in cold climates


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Ageing

The materials used for electrodes will generally deteriorate to some extent for

various reasons, for example:Chemical reactions (in acidic or alkaline soils)

Galvanic: due to stray DC currents in the earth, for example from electric

railways, etc. or due to dissimilar metals forming primary cells. Different soils

acting on sections of the same conductor can also form cathodic and anodicareas with consequent loss of surface metal from the latter areas.

Unfortunately, the most favourable conditions for low earth-electrode

resistance (i.e. low soil resistivity) are also those in which galvanic currents can

most easily flow.

Oxidation

Brazed and welded joints and connections are the points most sensitive to

oxidation. Thorough cleaning of a newly made joint or connection and wrapping

with a suitable greased-tape binding is a commonly used preventive measure.


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Main switch

The main switch fuse box isthere to help prevent electricalfires. If you overload a circuit,and it tries to draw more current

than the wire is supposed tohave, it will pop the fuse, causingan open circuit, and electricitystops flowing. The main switch

allows you to disconnect allelectricity coming into the home.


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(Residual current circuitbreaker)RCCB

A residual-current device (RCD), orresidual-current circuit breaker (RCCB), is an electricalwiring device that disconnects a circuit wheneverit detects that the electric current is not balancedbetween the energized conductor and thereturn neutral conductor. Ground Fault Condition

is defined as: An unintentional, electricallyconducting connection between an ungroundedconductor of an electrical circuit and the normallynon-current-carrying conductors , metallicenclosures, metallic raceways, metallic equipmentor earth. Such an imbalance may indicate currentleakage through the body of a person who is

grounded and accidentally touching the energizedpart of the circuit. A lethal shock can result fromthese conditions. RCCBs are designed todisconnect quickly enough to prevent injurycaused by such shocks. They are not intended toprovide protection against overcurrent(overload)

or short-circuit conditions.


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(Miniature cicuit breaker)MCB Miniature circuit breakers or MCBs are

used to replace fuses that protectindividual pieces of electrical equipmentand the circuits which supply them withpower.

In the case of tripping because of a current

overload, MCBs are very easy to reset,which is much simpler to do that having toreplace blown fuses. MCBs also trip to stopthe current from flowing much faster thanfuses can operate.

However MCBs are not better than fuses in

all respects: MCBs are much moreexpensive than fuses and they take upmore space, which is why fuses are stillused for some applications.


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Equipments


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Wiring installation


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2.1.3EXPLAIN SINGLE PHASE SYSTEM

Wiring specification

i. Size of cable1.5 mm - lamp circuit2.5 mm - socket4 mm - power circuit (water heater)

6 mm - power circuit (water heater)16 mm - main circuit

- Choosing suitable size of cable is to avoid the cablebecomes hot.

- BS7671 chapter 13 is referred.


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ii. Size of MCB

6 A lamp, fan, electric clock

16 A socket

20 A air-cond, hot water bath.


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iii. Types of wiring system

a. Surfaceb. Condiutc. Casingd. underground

earhting definition jiwinnie

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