S061-PPT_Safe Electrical Works Awarness.ppt

Electrical safe awarness

1. SAFE ELECTRICAL WORKS
UNDERSTANDING ELECTRICAL RISK
TO ENSURE HEALTH AND SAFETY
Health, Safety and Environment Training Course
“People, our most important asset”

2. ELETRICAL RISCK
COURSE TOPICS
Regulatoryconsiderations
TechnicalregulationsandworkinstructionsinSaipem
Basicsofelectrophysiology-definitions–quantities
Voltage,current,power,resistance,jouleeffect,etc.
Dangersduetophysicalcontactwithelectricpower
Electricshock,burns,tetanisation,heartfailure,respiratoryfailure,etc.
Causesofelectricalrisk
Directandindirectcontact,lightning,fireandelectricarc
Electricalrisk–preventionandprotection
Magnetic,thermalanddifferentialswitches,fuses,SPDs
Electricalequipmentonworksites
Electricsystemaccordingtothelaw,electricequipmentsupply,large
extraneousconductivepartstobeearthed
Cautionandpreventionmeasures
Sensiblebehavior

3. ELETRICAL RISCK
ELECTRICAL RISK IS AN INSIDIOUS
AND HIGH RISK BECAUSE OF THE
SERIOUSNESS OF THE INJURIES IT
MAY CAUSE

4. ELETRICAL RISCK
BASICS OF ELECTROPHYSIOLOGY
ELECTRICCURRENT
Aflowofelectricchargestravelling
insideaconductorwhichissubjectto
apotentialdifference.
Itpowersallequipment,systemsand
machineswhichneedenergyinorderto
operate,suchaslightingsystems,
productionmachines,handlingorlifting
systems,etc.
WATER
CURRENT
plastic
metal
atom
electron

5. ELETRICAL RISCK
ELECTRIC CURRRENT CAN BE:
DIRECT: the flow of electric
charges is constant over time
ALTERNATING : the flow of
electric charges varies over time
Characteristic current in a current-time
diagram
BASICS OF ELECTROPHYSIOLOGY

6. ELETRICAL RISCK
QUANTITIES WHICH CHARACTERISE
ELECTRIC CURRENT
POTENTIAL DIFFERENCE: the difference of electric potential between
two points of a conductor. It is called electric voltage. The unit of
measurement is Volt (V);
CURRENT INTENSITY : a physical quantity which measures the electric
charge crossing the section of a conductor within a time unit. The unit of
measurement is Ampere (A);
FREQUENCY : a physical quantity which measures the swings of the
current flow in the time unit. The unit of measurement is Hertz (Hz). In
Italy the electric current frequency distributed by the provider is 50 Hz (in
alternating current only).
BASICS OF ELECTROPHYSIOLOGY

7. ELETRICAL RISCK
ELECTRIC RESISTANCE
Electrical resistanceis a physical quantity measuring the tendency of a
conductor to oppose the passage of an electric current under tension. This
opposition depends on the material the conductor is made of, its
dimensions and its temperature.
Resistance is defined as R=V/I (potential difference/current intensity) =
Ω
The measurement unit of resistance is called ohm = Ω
The conventional resistance of a human being is 2500 –3000 Ω

8. ELETRICAL RISCK
JOULE EFFECT
One of the effects of the passage of
current through a conductor is its
heating, referred to as Joule effect,
defined as P= R i
2
, which is the power
dispersed in the resistor.
Usually it represents a loss of power,
but the Joule effect is positively used
in heaters, induction ovens, etc.

9. ELETRICAL RISCK
ELECTRIC POWER
ELECTRIC POWER IS DEFINED AS THE PRODUCT OF VOLTAGE BY CURRENT
AND IS EXPRESSED IN WATTS.
P = V x I (W)

10. ELETRICAL RISCK
DANGERS DUE TO PHYSICAL CONTACT WITH ELECTRIC POWER
AHUMANBODYTHROUGH WHICH
ELECTRIC CURRENT FLOWS IS
SUBJECTTOELECTRICSHOCKOR
ELECTROCUTION WHICH MAY
DEGENERATE INTOTETANISATION.
Thedangerforhumans startsfrom0.01
amperes, andadosageof0.10amperes
becomeslethalafterseveralseconds.

11. ELETRICAL RISCK
ELECTRIC SHOCK MAY
CAUSE:
BURNS
MUSCLE CONTRACTIONS
OR TETANISATION
RESPIRATORY ARREST
VENTRICULAR
FIBRILLATION AND
CARDIAC ARREST
DANGERS DUE TO PHYSICAL CONTACT WITH ELECTRIC POWER

12. ELETRICAL RISCK
BURNS
BURNSMOSTLYOCCURONTHE
SKINATTHEINPUTANDOUTPUT
POINTOFELECTRICCURRENT.
THESKINISTHETISSUEWHICH
PROVIDES THE HIGHEST
RESISTANCEANDWHICHHEATS
DUETOTHEJOULEEFFECT
UNTILBURNSARECREATED.
DANGERS DUE TO PHYSICAL CONTACT WITH ELECTRIC POWER

13. ELETRICAL RISCK
MUSCLE CONTRACTIONS
WHEN ELECTRIC CURRENT FLOWS
THROUGH MUSCLES, ITCONTRACTS
THEMFORASLONGASTHECURRENT
LASTS.
THISISOFTENWHYTHEVICTIMOFTHE
ACCIDENT CANNOT DETACHFROMTHE
POWERED AREA WHICH HE/SHE IS
GRASPING WITHTHEPALMOFHIS/HER
CLENCHEDHAND.
DANGERS DUE TO PHYSICAL CONTACT WITH ELECTRIC POWER

14. ELETRICAL RISCK
RESPIRATORY ARREST
RESPIRATORYARRESTISCAUSEDBYTHETETANISATIONOFTHE
MUSCLESRESPONSIBLE FORBREATHINGORBYTHEINHIBITION
OFTHERESPIRATORYCENTRES.
UNLESSARTIFICIALRESPIRATIONISGIVEN,DEATHOCCURSBY
CEREBRALHYPOXIAIN3/4MINUTES.
DANGERS DUE TO PHYSICAL CONTACT WITH ELECTRIC POWER

15. ELETRICAL RISCK
VENTRICULAR FIBRILLATION AND CARDIAC ARREST
THECONTRACTION OFTHECARDIACMUSCLEISDUETOELECTRICPULSES
GENERATED BYAPARTICULRNERVOUSCENTRE.
IFANEXTERNAL ELECTRICCURRENT WITHAREMARKABLY HIGHER
INTESITYISADDEDTOTHENORMALELECTROPHYSIOLOGICAL ACTIVITY,A
SUPERSTIMULATION OFTHEVENTRICULAR FIBRESISGENERATED, WHICH
CAUSESTHEMTOFIBRILLATE,MAKINGCARDIACACTIVITYINEFFECTIVE.
WHENCURRENTINCREASES,CARDIACARREST
OCCURS, ANDUNLESSCARDIAC MASSAGE
ANDARTIFICIALRESPIRATION ISGIVEN,
DEATHOCCURS IN3TO4MINUTES DUETO
CEREBRALHYPOXIA.
DANGERS DUE TO PHYSICAL CONTACT WITH ELECTRIC POWER

16. ELETRICAL RISCK
INTERNAL INJURIES FOR ELECTROPHYSICHAL, THERMAL
AND ELECTROCHEMICAL PHENOMENA
GENERATED BY ELECTROLYSIS IN ORGANIC LIQUIDS WHICH MAY
HAVE SERIOUS CONSEQUENCES EVEN AFTER A LAPSE OF TIME.
THE PREVALING EFFECT IS DUE TO THE DIRECT CURRENT.
THE ORGANS MOSTLY AFFECTED BY INJURIES ARE:
HEART RESPIRATORY MUSCLES NERVOUS SYSTEM
DANGERS DUE TO PHYSICAL CONTACT WITH ELECTRIC POWER

17. ELETRICAL RISCK
CURRENT INTENSITY AND ITS EFFECTS
Current
values
Definition Effects
1-3 mA PERCEPTION THRESHOLD No risk or danger for health
3-10 mA ELECTRIFICATION Generates a more or less severe tingling sensation
and can cause reflex movements.
10 mA TETANISATION Muscular contractions. If the component under
tension is grabbed with the hand, it may lead to
muscular paralysis, making it difficult for the victim
to detach.
25 mA RESPIRATORY
DIFFICULTIES
Caused by the contraction of the muscles
responsible for breathing and by the passage of
current through the nervous centers which regulate
the respiratory function.
25-30 mA ASPHYXIATION Respiratory muscle tetanisation may be such as to
cause death by asphyxiation.
60-75 mA FIBRILLATION If the current passes through the heart, it may alter
its regular functioning, causing an irregular and
disorderly contraction of cardiac fibres which may
cause death.

18. ELETRICAL RISCK
Zone 1:usuallyabsenceof
reactions,uptotheperception
threshold(handfingers)
Zone2:usuallynodangerous
physiologicaleffect,uptothe
tetanisationthreshold.
Zone3:pathophysiologicaleffects
mayoccur,usuallyreversible,
which increasewithcurrent
intensityandwithtime.These
include muscle contractions,
breathingdifficulties,increaseof
blood pressure, cardiac
disturbances(includingtemporary
cardiacarrest).
Zone 4:probableventricular
fibrillation,cardiac arrest,
respiratoryarrest,seriousburns.
CURRENT INTENSITY AND ITS EFFECTS
Danger curves of alternating current
Muscular contractions,
breathing difficulties,
arterial fibrillation,
temporary cardiac arrest
(usually reversible effects)
Possible ventricular
fibrillation, cardiac arrest.
Curves c2 and c3
correspond to a probability
of fibrillation of 5% and
50% respectively .
No dangerous
physiological
effect up to the
tetanisation
threshold
No reaction
up tothe
perception
threshold

19. ELETRICAL RISCK
ELECTRICAL RISK MAY BE DUE TO
DIRECT CONTACT
INDIRECT CONTACT
ATMOSPHERIC DISCHARGES
FIRE
ELECTRIC ARC

20. ELETRICAL RISCK
RISK OF DIRECT CONTACT
Load

21. ELETRICAL RISCK
RISK OF INDIRECT CONTACT

22. ELETRICAL RISCK
RISK OF ATMOSPHERIC DISCHARGE (LIGHTNING)

23. ELETRICAL RISCK
Directandindirectelectrocution:lightningcancausehealth
damageindirectformifthebodyishitbyatmosphericdischarges,orin
indirectformifitishitbythereturncurrentthroughtheground(step
current).Moreseriousdamageincludesrespiratoryarrestanddeath.Less
seriousdamagecanbeparalysis,amnesiaandunconsciousness.
ELECTROCUTION

24. ELETRICAL RISCK
STEPVOLTAGE
Stepvoltageisthepotential
differenceonthegroundbetween
thetwopointswherethefeetrest.
Thewiderthestep,thehigherthe
potentialdifferenceandthehigher
thestepcurrentthatflowsthrough.

25. ELETRICAL RISCK
FIRE
FIREINEQUIPMENTORELECTRICSYSTEMS ISCAUSEDBY
FAILUREORPOOROPERATION/USE OFTHEEQUIPMENT OR
SYSTEM.

26. ELETRICAL RISCK
FAILURE OR POOR
OPERATION/USE OF
ELECTRIC
SYSTEMS/EQUIPMENT
1.OVERLOADS
1.OVERVOLTAGES
1.SHORT CIRCUITS
1.FAILURE OF
CONDUCTOR
INSULATION
1.ELECTRIC ARCS

27. ELETRICAL RISCK
ELECTRIC ARC
PHYSICAL PHENOMENON OFAIR IONIZATION WITH THE
PRODUCTION OFHIGHHEAT,TOXICGASESANDULTRAVIOLET
RAYS
CAUSED BY
1.SHORT CIRCUITS
2.OVER VOLTAGES (high potential
difference between two conductors
where air is insufficient for
insulating purposes)
3.LIGHTNING

28. ELETRICAL RISCK
ELECTRICAL RISK -PREVENTION AND PROTECTION
Protectionagainstdirectcontact
Protectionagainstdirectcontactisperformedthroughthe
segregationofpoweredelectricpartscarriedoutthrough
physicalinsulation(segregationofconductors,confinementof
poweredparts,insulatingshield,etc.),orthroughmechanical
spacerswhichpreventtheapproachtopoweredparts.

29. ELETRICAL RISCK
Protectionagainstindirectcontact
Protectionagainstindirectcontactiscarriedoutthroughsystem
basedmeasures,suchasearthingofmetalequipment,and
differentialprotection,consistingofparticulardevices(circuit
breakers)whichinterruptthepowerupstreamanddispersecurrent
totheground.
ELECTRICAL RISK -PREVENTION AND PROTECTION

30. ELETRICAL RISCK
EARTHING
DEFINITION
Earthing means channeling into the ground the failure currents which
represent a danger to the safety of people
MAIN TYPES
Protection earthing
Earthing for temporary works
Operation earthing

31. ELETRICAL RISCK
ESSENTIAL ELEMENTS OF AN EARTHING SYSTEM
Ground electrodes (stakes, plates or conductors)
Conductor network (to connect the parts of the system to
be earthed)
SYSTEMS ACCORDING TO THE TYPE
OF EARTHING CONNECTION
TT System TN System IT System
ELECTRICAL RISK -PREVENTION AND PROTECTION

32. ELETRICAL RISCK
SYSTEMS ACCORDING TO THE EARTHING CONNECTION
ELECTRICAL RISK -PREVENTION AND PROTECTION

33. ELETRICAL RISCK
CONTACTVOLTAGE(Uc)
Contactvoltageisthevoltagetowhichthehumanbodycanbesubjectedafter
contactwiththemetallicframesandstructureswhich,duetopossibleinternal
faults,mayhavebecomeenergised,despitenotnormallybeinglive.
STEPVOLTAGE(Up)
Stepvoltageisthevoltagewhich,duringtheoperationoftheearthsystem,
canresultbetweenthefeetofapersonstandingnearalivegroundedobject.
Protectionagainststepvoltagemainlyinvolvesthemiddleandhighvoltage
system.
ELECTRICAL RISK -PREVENTION AND PROTECTION

34. ELETRICAL RISCK
CONTACT AND STEP VOLTAGE
ELECTRICAL RISK -PREVENTION AND PROTECTION

35. ELETRICAL RISCK
ELECTRICAL RISK -PREVENTION AND PROTECTION

36. ELETRICAL RISCK
DIFFERENTIAL SWITCH
ELECTRICAL RISK -PREVENTION AND PROTECTION

37. ELETRICAL RISCK
DIFFEFRENTIAL SWITCH
Protection against both direct and
indirectcontact
ELECTRICAL RISK -PREVENTION AND PROTECTION

38. ELETRICAL RISCK
PROTECTION AGAINST INDIRECT CONTACT
DOUBLE-INSULATION ELECTRICAL EQUIPMENT
Class II components
Protection against indirect contact, with no
automatic interruption of the circuit, is allowed
by CEI standards 64/8 in the case of double-
insulation electrical equipment.
DOUBLE INSULATION SYMBOL
ELECTRICAL RISK -PREVENTION AND PROTECTION

39. ELETRICAL RISCK
PREVENTION AND PROTECTION MEASURES
AGAINST ELECTRICAL RISK
LIGHTNING STRIKES
LIGHTNINGRODSARENORMALLY PLACEDON
THEHIGHEST BUILDING INTHEAREATO
EXPLOITTHETENDENCYOFLIGHTNINGTOHIT
ANYTHINGTHATISPOINTED.
THELIGHTNING RODISCONNECTED TOA
FARADAY CAGEINTURNCONNECTED TOAN
EARTHING SYSTEM THATCHANNELS THE
CURRENTINTOTHEGROUND.
ELECTRICAL RISK -PREVENTION AND PROTECTION

40. ELETRICAL RISCK
LIGHTNING RODS
ELECTRICAL RISK -PREVENTION AND PROTECTION

41. ELETRICAL RISCK
FARADAY CAGE
TENDENCY OF CURRENT TO RUN THROUGH THE
EXTERNAL SURFACE
ELECTRICAL RISK -PREVENTION AND PROTECTION

42. ELETRICAL RISCK
GROUND WIRES
Conductors
Shield wires
Shelves
Insulators
Supports
Insulators
TENDENCY OF CURRENT TO RUN
THROUGH THE EXTERNAL
SURFACE
ELECTRICAL RISK -PREVENTION AND PROTECTION

43. ELETRICAL RISCK
PROTECTION MEASURES AGAINST THE RISK OF FIRE DUE TO
OVERLOAD
OVERLOAD :CONDITION OCCURRING WHENANELECTRICCABLEOR
MACHINEHASACURRENTTHATISHIGHERTHANTHENOMINAL ONE
FORWHICHITHASBEENSIZEDANDDESIGNED.
THEOVERLOAD GENERATES PROGRESSIVE OVERHEATING OFTHE
PARTSAFFECTED, ATFIRSTCAUSING DETERIORATION OFTHE
INSULATING PARTS AND,SUBSEQUENTLY, SHORT CIRCUIT AND
THENFIRE.
ELECTRICAL RISK -PREVENTION AND PROTECTION

44. ELETRICAL RISCK
THERMAL SWITCH
ASPECIALOVERLOAD PROTECTION SWITCHTOBE
INSTALLED UPSTREAM OFTHESYSTEM TOBE
PROTECTED ANDWHICHOPENSUPTHECIRCUITS
WHENTHEREISACURRENT HIGHERTHANTHE
NOMINALONE.
ELECTRICAL RISK -PREVENTION AND PROTECTION

45. ELETRICAL RISCK
PROTECTION MEASURES AGAINST THE RISK OF FIRE DUE TO
SHORT CIRCUIT
SHORT CIRCUIT : A PHENOMENON WHICH
OCCURS WHEN TWO PHASES (PHASE AND
NEUTRAL, PHASE AND GROUND OR PHASE AND
PROTECTION CABLE) COME INTO CONTACT.
During a short circuit, resistance is equal to zero,
the voltage is equal to zero and the current tends to
infinite generating a sharp and sudden overheat due
to the joule effect which in turn causes a fire.
ELECTRICAL RISK -PREVENTION AND PROTECTION

46. ELETRICAL RISCK
MAGNETIC SWITCH
ASPECIALSHORT CIRCUITPROTECTION
SWITCHTOBEINSTALLEDUPSTREAMOFTHE
SYSTEM TOBEPROTECTED ANDWHICH
OPENSUPTHECIRCUITWHENTHEREISA
SHORTCIRCUIT.
ELECTRICAL RISK -PREVENTION AND PROTECTION

47. ELETRICAL RISCK
FUSE
ASPECIALELECTRICPROTECTION DEVICE
TOBEINSTALLED UPSTREAM OFTHE
SYSTEMTOBEPROTECTED ANDWHICH
GETSBURNEDDUETOTHEJOULEEFFECT
(OPENINGTHECIRCUIT)WHENITISRUN
BYACURRENTHIGHERTHANTHENOMINAL
ONE.
ELECTRICAL RISK -PREVENTION AND PROTECTION

48. ELETRICAL RISCK
DIFFERENTIAL MAGNETIC -THERMAL SWITCH
MAGNETIC
THERMAL
DIFFERENTIAL
SHORT CIRCUITS
OVERLOADS
DIRECT AND
INDIRECT CONTACT
ELECTRICAL RISK -PREVENTION AND PROTECTION

49. ELETRICAL RISCK
PROTECTION MEASURES AGAINST THE RISK OF FIRE DUE TO
OVERVOLTAGE
ANSPDISASPECIALSURGEPROTECTION
DEVICETOBEINSTALLEDUPSTREAM OFTHE
SYSTEM TOBEPROTECTED ANDWHICH
MANTAINS THECIRCUITNORMALLY OPEN
BETWEEN THEPHASESANDTHEGROUND.
DURINGANOVERVOLTAGE ITTEMPORARILY
CLOSES UPINORDER TOCHANNEL THE
OVERVOLTAGE TOWARDS GROUND.
Limit of overtension to
values not dangerous
for the apparatus
Deviation of impulsive
current to the ground
With SPD
ELECTRICAL RISK -PREVENTION AND PROTECTION

50. ELETRICAL RISCK
ON THE WORKSITE –THE ELECTRIC SYSTEM
ENEL delivery point in
LV at 220/380 V or
generator
Delivery boards with
middle-high
calibration protection
equipment
Cable troughs,
earthing system and
inspection wells
Users with high-
sensitivity
protection
equipment
ELECTRICAL RISK -PREVENTION AND PROTECTION

51. ELETRICAL RISCK
ELECTRIC SYSTEM
ACCORDING TO THE LAW
DECLARATION OF CONFORMITY
ELECTRICAL RISK -PREVENTION AND PROTECTION

52. ELETRICAL RISCK
ELECTRIC EQUIPMENT ON THE WORKISITE
Welders
Electrode holder furnaces
Wheels and sanders
Boring machines
Lathes-Screwers
Cranes
Lights–sirens-alarms
Boilers-heaters
Refrigerators/freezers–PC -phones
Dewatering pumps and saws
Piglets
Jackhammers
Photocopiers–printers–UPS
Fax machines and scanners
Test benches on the worksite
Cement mixers
Displacement compressors and
APs
Induction furnaces
Fuel distributors

53. ELETRICAL RISCK
ELECTRIC EQUIPMENT SUPPLY
OPERATION AND MAINTENANCE BOOKLET/
MANUAL+ MAINTENANCE REGISTER
ELECTRIC EQUIPMENT ON THE WORKISITE

54. ELETRICAL RISCK
EARTHING OF ALL EXTERNAL CONDUCTIVE PARTS
Fences
Switchboards
Containers
Scaffolding
Tanks
Warehouses
ELECTRIC EQUIPMENT ON THE WORKISITE

55. ELETRICAL RISCK
Generators and
shelters
Buried pipes
Compressor batteries
ELECTRIC EQUIPMENT ON THE WORKISITE

56. ELETRICAL RISCK
Runners
Connecting
pipes
Displacement compressors
ELECTRIC EQUIPMENT ON THE WORKISITE

57. ELETRICAL RISCK
CAUTION AND PREVENTION MEASURES
Do not remove the plug from the socket
by pulling the wire. You could break the
cable or external wrapping, uncovering
the energised parts.
If the plug does not come out of the
socket, do not pull it with excessive force,
otherwise you risk tearing the socket out
of the wall.
RISK: DIRECT CONTACT

58. ELETRICAL RISCK
Do not insert more than one electric device into
one socket before evaluating its load
absorptions and capacity, otherwise you run
the risk of overheating the socket with the
danger of overload/short circuit and fire.
OVERLOAD RISK
FIRE RISK
CAUTION AND PREVENTION MEASURES

59. ELETRICAL RISCK
Before replacing a light bulb, turn off the
mains.
RISK: DIRECT CONTACT
CAUTION AND PREVENTION MEASURES

60. ELETRICAL RISCK
Always use extension cables with a size
appropriate to use. The supported current,
in Ampere (A), or maximum power, in
Watt (W), is indicated on all sockets and
adaptors.
Adaptors with 16 A plugs and 10 A
sockets are acceptable; ones with 10 A
plugs and 16 A sockets are forbidden.
OVERLOAD RISK
FIRE RISK
CAUTION AND PREVENTION MEASURES

61. ELETRICAL RISCK
German-typeplugs(Schuko)canbeinsertedinto
Italian-typesocketsonlyusinganadaptorwhich
transferstheearthingconnectionthroughthe
lateralsheetstoamiddleplug.Itisstrictly
forbiddentoforcetheinsertionofSchukoplugsinto
Italian-typesockets,asinsuchcasestherewillbe
noearthing.
RISKOFFAILEDCIRCUIT BREAKER INTHE
EVENTOFINDIRECTCONTACT
CAUTION AND PREVENTION MEASURES

62. ELETRICAL RISCK
Donotperformanyoperationonelectric
equipmentwhenyourhandsarewetor
clammy.
RISK:DIRECTCONTACT
CAUTION AND PREVENTION MEASURES

63. ELETRICAL RISCK
Do not install several multiple adaptors one on top
of the other.
OVERLOAD OR OVERHEATING RISK DUE TO
BAD CONTACT
CAUTION AND PREVENTION MEASURES

64. ELETRICAL RISCK
Iftheequipment and/or electric
components showsignsofstructural
failureordamage,theymustbediscarded
andreplaced.
RISK:DIRECTCONTACT
CAUTION AND PREVENTION MEASURES

65. ELETRICAL RISCK
Use multi-plug adaptors equipped with
incorporated thermal switch
PREVENT OVERLOADS
CAUTION AND PREVENTION MEASURES

66. ELETRICAL RISCK 66
End of presentation