IGC2 Element 5 Electrical

7/21/2019 IGC2 Element 5 Electrical

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IGC 2 : ELEMENT 5IGC 2 : ELEMENT 5

ELECTRICAL HAZARDSELECTRICAL HAZARDS

& CONTROL& CONTROL



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PRINCIPLES OF ELECTRICITYPRINCIPLES OF ELECTRICITY

• Electric current (I): is the flow ofelectrons from one position to another;

• The potential difference of electricity ismeasured in Volts

• Conductor: is the substance throughwhich electric current flows

• The resistance of conductors to the flowof current is measured in Ohms

I = V/R



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• Conductors are materials that allow electriccurrent to flow easily (low resistance) e.g.copper, steel, water… etc.

• Insulators , on the other hand, have highresistance e.g. rubber, wood… etc.



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Basic Circuitr• Flow of current needs a closed circuit

e.g. electrical lamp battery !oined

together by a conductor.• !ain "a#ar$s associat%$ &it'

El%ctricit



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!)IN ")*)R+S OF ELECTRICITY!)IN ")*)R+S OF ELECTRICITY

ELECTRIC S"OC,-"ccurs when the body becomes part

of the electrical circuit; the currententers the body at one point andmust leave at another.

The effect of an electric shoc# on aThe effect of an electric shoc# on ahuman body depends on $human body depends on $

• %urrent and voltage• &esistance

• 'ath through body• uration of shoc#.



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Three basic ways to be shoc#ed$• %ontact with both wires of an electrical

circuit.• %ontact with one wire of an electrical circuit

and ground source.• %ontact with ground source and a metal part

that is in contact with a wire of an electrical

circuit.



• Direct effect — in!ury or death can occur

when electric current flows through ahuman body.• %urrent *+ m can result in death. (-o

et /o)• Indirect effect — human reaction to

current flow may result in a fall ormovement into an operating machine(secondary ha0ards).



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EFFECTS OF ELECTRIC S"OC, ON " !)NEFFECTS OF ELECTRIC S"OC, ON " !)NBO+YBO+Y

• 1T"' T23 23 &T1T"' T23 23 &T

• 45&- T23 167-45&- T23 167-

• "11 "F 851% 3"11 "F 851% 3%"-T&"%"-T&"

• 1T"' 4&3 T27-/1T"' 4&3 T27-/

• -3&9"51 1:1T38-3&9"51 1:1T383FF3%T13FF3%T1



E %cts caus%$ curr%nt lo&in5t'rou5' t'% o$ 6•With increasing AC, the victim:

notices a tingling sensation muscles contract sensation of heat at <= m , victim cannot let go of

conductive surface (let>go threshold)

at <++ m , ventricular fibrillation ofheart . . . death.



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2eavy current flow can result in severe burns and heartparalysis.9aries with$• amount of moisture on s#in• pressure applied to contact point

• %ontact area.• 8oisture reduces resistance.• 1everity of shoc# increases with increasingpressure.

• arger the contact area, lower the resistance.



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+uration o S'oc8

• 2as a significant effect on finaloutcome$ 1hort ? may only be a painful e@perience.

t fibrillation threshold, a few secondsmay be fatal. t high currents ( <++ m ), death is

inevitable with any shoc#.



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E %ct o El%ctric S'oc8 on "u9an o$ -

•S8in•8ade up of * layers "uter layer is mostimportant•Ahen dry, may have a higher resistance, butdrops dramatically when wet•&esistance varies with different parts of thebody and the individual





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!uscl%• %ontrolled by electrical impulses

delivered by nerves• 3lectric shoc# can cause a loss of

muscular control, resulting in theinability to let go of an electricalconductor

• 7t also leads to stop of breathing



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FIRST )I+ FOR ELECTRIC S"OC,FIRST )I+ FOR ELECTRIC S"OC, %all for help%all for help 1ecure the seen turn off power1ecure the seen turn off power

supplysupply 8a#e sure victim has clear airway,8a#e sure victim has clear airway,

breathing not bleedingbreathing not bleeding 7f victim is breathing, put them in7f victim is breathing, put them in

recovery position till help arrivesrecovery position till help arrives 7f not breathing, start administering7f not breathing, start administering

%'&%'& Treat 4urnsTreat 4urns

• &emain with the victim and&emain with the victim andprovide reassurance tillprovide reassurance tillambulance arrivesambulance arrives



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OT"ER ELECTRIC)LOT"ER ELECTRIC)L

")*)R+S")*)R+S• 3 3%T&7% 45&-13 3%T&7% 45&-1

• 3 3%T&7% F7&31 3 3%T&7% F7&31 3C' "17"-13C' "17"-1

• '"&T 4 3 3 3%T&7%'"&T 4 3 3 3%T&7%3D57'83-T3D57'83-T

• 13%"- &: 2 E & 1$13%"- &: 2 E & 1$71%511 A7T2 3C 8' 31



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El%ctrical Fir%s : E;<losions-• 3lectricity is one of the most common causes of fire at home

and wor#place.• "verloaded circuits e.g. too many appliances plugged into a

multi soc#et adaptor. ac# of ventilation leading to overheating• efective or misused electrical e uipment is a ma!or cause

2igh resistance is a primary source of e@plosion.

• 2igh>resistance connections occur when wires are improperlyspliced or connected to other components (outlets andswitches).

• 3@plosions "ccur when electricity provides a source of ignitionfor an e@plosive mi@ture in the atmosphere.

• 3@plosions can be ignited by overheated conductors ore uipment.



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Porta l% El%ctrical E ui<9%nt-• -ot part of electric a fi@ed installation but may be connected to a

fi@ed installation by means of a fle@ible cable or a soc#et plug.• 7t may be hand held or hand operated while connected to the

supply.• %auses appro@imately G=H of reported electrical accidents.• 5se of defective I unsuitable e uipment the misuse of

e uipment.• Faulty fle@ible cables, e@tensions, leads, plugs soc#ets.• 5sually due to inade uate maintenance inspection use in wet

conditions.• ccidents occur when contact is made with some part of the tool

which has become live, while user is standing in contact with anearthed conducting surface.



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T"E PL >

• -o fuse or fuse replaced by nail, etc.• amage to plug casing

• 7ncorrect wiring inside plug• 3arth wire detached from connection



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T"E C)BLE/LE)+

• 4eing run over by vehicles• ragged over rough surfaces• Trapped in machinery• 3@posed to hot surfaces or corrosive

chemicals• %ontinuous fle@ing

• 7nsulation failure



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T"E ?OINTS )N+ CONNECTIONS

• 8a#eshift, temporary connections• eads pulled out of cord grips• %onnections wired incorrectly so that

metalwor# becomes live• Arong connections• 'oor earth connections preventing fuse

from wor#ing



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T"E )PPLI)NCET"E )PPLI)NCE

• amage casing

• Aorn or damaged connections

• C'%c8lists 9a % $ra&n u< to

%nsur% t'% sa %t o t'% a o@%6



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CONTROL !E)S RES FOR ELECTRIC)LCONTROL !E)S RES FOR ELECTRIC)L")*R)+S")*R)+S

<.<. 13 3%T7"- 13 3%T7"- 157T 47 7T: "F157T 47 7T: "F3D57'83-T3D57'83-T

G.G. 7-1'3%T7"- 7-1'3%T7"- 8 7-T3- -%38 7-T3- -%31T& T3/7311T& T3/731

*.*. 513 "F513 "F

'&"T3%T793'&"T3%T7931:1T3811:1T381



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The precautions re uired to prevent accidents using portablee uipment are$

•&educed voltage operation•5se of residual current circuit brea#ers• pparatus and cables should be protected against overload by fuses andIor circuit brea#ers• ll cables should be insulated and protected against mechanical damage•%orrect types of sheathing to suit wor#ing conditions•1ufficient soc#et outlets to minimise the need for trailing cables•The use of cable drums wherever possible•%orrect connections•&educed voltage operation•&egular inspections and chec#s to remove damaged e uipment•'roperly trained operators



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INSPECTION )N+ !)INTEN)NCE OFINSPECTION )N+ !)INTEN)NCE OFELECTRIC)LELECTRIC)L EA IP!ENTEA IP!ENT

T <%s o Ins<%ction• s%r c'%c8s• For9al @isual ins<%ction• Co9 in%$ ins<%ction an$ t%st

Porta l% )<<lianc% T%stin5 P)TD



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s%r c'%c8s

• Carri%$ out % or% us% $ail D toc'%c8 int%5rit o <lu5 ca l% an$% ui<9%nt or si5ns an$$a9a5%/o@%r'%atin56



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For9al @isual ins<%ction

• %arried out wee#ly or fortnightly(depending on e@tent of conditions ofuse) by an appointed person (with

electrical #nowledge) s 5ser %hec#(but more thorough) and will includechec#ing fuse ratings and connectionsto plug and appliance.



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Co9 in%$ ins<%ction an$ t%stPorta l% )<<lianc% T%stin5 P)TD

•Carri%$ out a co9<%t%nt <%rson ats<%ci i%$ int%r@als consistin5 o %art'

on$in5 insulation r%sistanc% an$%art' l%a8a5% t%sts6 Functional c'%c8son a<<lianc%



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Factors affecting fre uency of inspection andtest$

•8anufacturerJs recommendations• ge of e uipment•&obustness of e uipment• ouble insulated or earthed

•Type of cable (e.g. armoured)•3@tent of use•5sers of e uipment•3nvironment of use (mechanical damageIwet environment etc.)•Foresee ability of abuse or misuse•2istory of e uipment (results of previous inspections)



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%entral records of inspectionItesting of portableelectrical appliances should be #ept$

•For inspection by authorised person (e.g.enforcing authority)•7n event of test label being removed fromappliance or plug•To ensure test fre uencies maintained•&ecord actions if faults rectified



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'recautions for electrical safety in office environments couldinclude$•3 uipment is of approved standard e.g. 41I3- standard

•8aintenance of fi@ed electrical installations•There is a means of isolation• ll connections, wiring free from damage•%orrect fuses•'lug correctly wired• void overloading of outlets•1witch off appliances when not in use•8aintain good house#eeping around electrical e uipment•7f re uired portable appliance testing in date•1ystem not overloaded•%ables correctly routed to avoid ha0ards•&% s used•1ystem for reporting defects



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OR,IN> ON LIVE EA IP!ENT

Aor# should not be done on live e uipment unless$• 7t is unreasonable in all circumstances for the

conductor to be dead, e.g. fault finding• 7t cannot be carried out remotely or with barriers• 1uitable precautions are ta#en to prevent in!ury



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1uitable precaution for wor#ing live are$• 'eople who are properly trained and competent

• ccompanied by another person• 'rovision of ade uate information• 1uitable insulated tools• 7nsulated barriers or screens

• 1uitable instruments and test probes• 'ersonal protective clothing• &ubber mats• 'ermit>to>wor#• &estricted access



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S%con$ar "a#ar$s-• brasions, impact, noise vibration.

•3@tension cables representing tripping ha0ards.•3lectric shoc# may cause victim to fall from height

could cause collision with a vehicle or movingpart of machinery.

•4urns lead to suffocation, structural collapse infections… etc.

Control !%asur%s or El%ctrical "a#ar$s-

• 1election 1uitability of 3 uipment• 5se of 'rotective systems• 7nspection maintenance strategies



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1G S%l%ction : Suita ilit o E ui<9%nt-

•The selected e uipment must be safe 1uitable for the tas# demanded or else it willbecome overloaded.•3 uipment must only be used within the ratingperformance given by the manufacturer.•3 uipment should be installed to a recogni0edstandard be capable of being isolated in casesof emergency.• esigned free from any foreseeable ris#s Iordefects.



3.

PROTECTIVE SYSTE!SPROTECTIVE SYSTE!S

Fuse: A thin strip of conducting wire which will melt to break the circuit at excessive currents.

Advantages:• Protection against overload before damage takes place.• Can be easily replaced & the cost is low

Limitations:• Not effective protection against electric shock.• Needs examination & Inspection



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Isolation: More than switching off the current; it creates a barrier between the e uipment & electrical supply whichonly an authori!ed person should be able to remove.

Advantages:• Can be locked off.• "nsures safety during the work process.

Limitations:• #f not locked off$ might be reconnected by mistake.




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Residual Current evices RC ! devices that will rapidly cut the electricalsupply to the e uipment in few seconds$ in case it senses a few milli ampsdifference in current.

Advantages:• %est protection against electric shock • ery sensitive to current differences between live & neutral power lines.• Protect installations against 'ire.• Can be easily tested.

Limitations:• (ill not prevent shock$ but will reduce the duration to the time the )C*

need to operate.• #n addition to )C*$ the protected e uipment must be properly protected

by insulation & enclosure.• *oesn+t provide overload protection.




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Eart'in5%reating a low resistance path to the earth ; incase of fault, such as a brea# in the circuit, the

current, will return directly to earth. This can bedone by having one of the circuit conductorssolidly connected to the earth. This reducesvoltage build up prevents accidents.



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R%$uc%$ Lo& Volta5% S st%9s&ecommended when wor#ing conditions arerelatively severe; wet conditions, heavy fre uent use of e uipment.'ortable tools should operate on <<+ volts orless with centre tapped to earth at == volts.

t this level of voltage, the effect of shoc#should not be severe.

5se of 4attery operated hand tools..



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+ou l% Insulation5ses two independent layers of insulation overthe live conductors.3ach layer alone being ade uate to insulate thee uipment safely.8ust be inspected maintained properly discarded if damaged.

+ou l% Insulation Si5n



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OT"ER CONTROLSOT"ER CONTROLS

• 3 &T27-/3 &T27-/• &3 5%3 "A 9" T /3&3 5%3 "A 9" T /3

1:1T3811:1T381

• "54 3 7-15 T 7"-"54 3 7-15 T 7"-• 7-1'3%T7"- 8 7-T3- -%37-1'3%T7"- 8 7-T3- -%3• 513& %23%61513& %23%61• &3%"& 1 "F 7-1'3%T7"- &3%"& 1 "F 7-1'3%T7"-

T31T7-/T31T7-/



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Ins<%ction : !aint%nanc% Strat%5i%sH loo# for$

•The cleanliness of insulator conductor surfaces

•8eans of identifying the e uipment to be tested•%ompetence of those who will underta#e the testing•8echanical 3lectrical integrity of all !oints connections•The calibration, condition operation of protection e uipment

•The legal re uirements for 'ortable ppliances Testing•&ecording, monitoring reviewing system•Training re uirements.



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s%r C'%c8sH prior to each use

• &ecent portable appliance test label• 9isible bare wires• %ables covering free from damage, cuts abrasions• Too long, too short cable• 'lug in good condition• -o "verheating or burning mar#s• &% wor#ing effectively (press KtestK button)



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For9al Ins<%ction : t%sts

• 8ust be carried out by competent personnel• Faulty e uipment to be ta#en out of service• "nly the plug cover to be removed to ma#e sure of

the correct fuse in place• %hec# correct polarity• ll cables B cores are effectively terminated• 3 uipment is suitable for the environment



4.

Fr% u%nc o Ins<%ction : t%stin5H based on

•&is# assessment related to usage•Fre uency of usage•"perational environment load

•Type of e uipment, the place manner it will be used•-o KcorrectK interval of time for inspection.



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R%cor$s o Ins<%ction : t%stin5

• 1chedules with details of inspection maintenanceperiods must be recorded documented.

• lways be #ept up>to>date with an audit procedure inplace to monitor the records.

• 8ust be retrievable; whether a hard copy ofelectronic copy

• 3 uipment should be labeled with the date of lastcombined test 7nspection.



Porta l% )<<lianc% T%stin5)$@anta5%s-• 3arly discovery of incorrect supply I inade uate e uipment• iscovery of incorrect fuses• 3arly recognition of serious e uipments faults e.g. poor earthing,

damaged cables…etc• &eduction in number of electric accidents• 8onitoring the misuse of portable appliances• 7ncrease awareness of electrical ha0ardsLi9itations-• 8ight have e@cessive cost if done too often• 8isuse over use between tests• 1ome unauthori0ed e uipment with no record might never be tested

e.g. personal #ettles• 8ust be done by competent person• 7mproper calibration of testing e uipment.

Documents

IGC2 Element 5 Electrical