ppt 9. electrical wiring - large font.pptx

8/10/2019 ppt 9. Electrical Wiring - Large Font.pptx

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Electrical Wiring

EE 2802 AppliedElectricity


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Electrical Wiring LearningOutcomes At the end of this unit, you will be able to;1. Describe the wiring regulations2. Recognize standard wiring symbols

3. Describe the typical layout of residential andindustrial distribution systems

4. Select the appropriate cable size for a giveninstallations using voltage drop calculations

5. Identify and compare possible methods tominimize the cable size and hence the cost

2EE2802 - Applied Electricity


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Contents

1. Wiring regulations2. Wiring symbols3. Selection criteria of cables4. Residential distribution systems5. Commercial / industrial distribution

systems6. Earthing / Grounding



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1. Wiring Regulations

Designed to protect persons and propertyfromElectric shock

FireBurnsInjury from mechanical movement of

electrically actuated equipment 4EE2802 - Applied Electricity


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In Sri LankaIEE Wiring Regulations

Issued by;Institution of Engineering and Technology IET

Other regulations: Electricity Act of Sri Lanka ICTAD SCA8 (Institute for Construction

Training and Development) Power company requirements

Product manufacturers requirements 5EE2802 - Applied Electricity


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2. Wiring Symbols

Standard symbols for electricalconstruction drawings is published by;

ANSI- American National Standards

Institute



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Connections



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Switch symbols



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Lighting outlets & fixture symbols



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3. Selection Criteria of Cables In accordance with the IEE Wiring Regulations

we should consider;

Current carrying capacity Ambient temperatureCable groupingThermal enclosure

Voltage dropDisconnection time (if protected by

breakers no need to consider) 11EE2802 - Applied Electricity


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Step 1:Calculate the current required by theappliancesIb = Appliance Power / Supply Voltage

Step 2:Choose the protecting device (breaker)In = Current rating of the protecting deviceIn > I b



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Step 3:From IEE Wiring Regulation tables find thecorrection factors for

Ambient temperature (C a )Cable grouping (C g)Thermal enclosure (C i)

Step 4:Calculate the current carrying capacity (I z)

Consider the worst case 13EE2802 - Applied Electricity


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Step 5:Select the suitable cable size for thecalculated I z

Step 6:Calculate the voltage dropBetween distribution board and theapplianceShould be less than 4%Use voltage drop in mV/A/m from tables



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16

ConsumerUnit Heater

50mm8 cables in a bunch

50 0CThermally insulated with glass fiber

240V

3kW

15AMCB

14m

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Current required by the appliance (I b)= Appliance Power / Supply Voltage

Check whether I n > I b condition is satisfiedIn = Current rating of the protective device

Find 3 correction factors (Ca, C

g & C

t)

Consider the worst case combination (C a , C g &C t)

Calculate the current carrying capacityIz = I n / (combination of correction factors)

Select suitable cable size for I zCalculate voltage drop and check whether it isbelow 4% 17EE2802 - Applied Electricity


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4. ResidentialDistributionSystems



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Consumer Unit

Distribute electrical power into branch circuitsConsists followings in a common enclosure:

1. Main switch

2. One or more RCDs (or RCCBs)3. Protective circuit breaker for each

branch circuit



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5. Commercial / IndustrialDistribution Systems

Apart from above, consists of;Switching devices- to start and stop power flowPanel boards

Transformers



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6. Earthing / GroundingTypes of earthing arrangements:

TN systemTT systemIT system

In Sri Lanka TT systemSupply authority earth and the installationearth is independentCommonly a galvanized iron pipe

24EE2802 Applied Electricity

ppt 9. electrical wiring - large font.pptx

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