Electrical Hazards and Control

IGC 2 El t 4IGC 2 – Element 4

Element No.

Title

1 Movement of People and Vehicles – Hazards and Control

2 Manual and Mechanical Handling –Hazards and Control

3 Working equipment hazards and Control

4 Hazards and risks associated with Electricity at work (Electrical hazards and control)hazards and control)

5 Fire hazards and control

6 Chemical and biological health hazards and control

7 Physical and psychological health hazards and control

8 Construction activities - hazards and control

Electrical Hazards and ControlElectrical Hazards and Control(Duration : 3 Hrs.)

Element 12 : Electrical Hazards and Control

LEARNING OUTCOMES :

• Basic circuitry• Relationship between voltage, current and

resistance, frequency, q y• Hazards of Electricity• Control Measures

D fi ti f El t i lDefinations of Electrical Terms1. Volt: The unit of measurement of electrical pressure

2. Ampere (Current): The unit of measurement of electric current flow

3. Ohm (Resistance): The unit of measurement of electrical resistance

Relationship of Volt (V), Current (I) & Resistance (R)

As per Ohm’s Law: V = IR or I = V/R

C d tConductors:Conductors: Some materials allow electric current to floweasily. These materials (e.g. Metals such as copper andsteel and other substances such as water) have lowresistance and are called Conductorsresistance and are called Conductors

I l tInsulatorsInsulators: Some materials have high resistance toelectric current (e.g. plastic, rubber wood) and arecalled insulators.

M i D f El t i itMain Dangers of Electricity• Electric Shock• Arching• Fire and explosion• Burns

El t i l S f tElectrical Safety

Human Resistance Values for Various Skin-contact conditions

Body Resistance Value

Dry skin 1,00,000 to 6,00,000 ohms

Wet Skin 1000 ohms

Internal Body (hand to foot) 400 to 600 ohms

Ear to Ear (about) 100 ohmsEar to Ear (about) 100 ohms

El t i l S f tElectrical SafetyEffect of Current on Human Body

Effect of current Milli Amps.

Shock, Let – go border line of painful shock, Muscles still under control

<= 10 mA>= 10 mA

Muscle control affected 15 mAMuscle control affected 15 mA

Breathing difficulties start 20 mA

Severe shock & possible death due to rapid, uncoordinated series of contraction of heart muscles causing irregular heart beat & possible death

50 mA> 3 secheart beat & possible death > 3 sec.

Electric Shock

Flow of electric current through humanFlow of electric current through human

body results in electric shock

Severity of Shock Depends upon:

Electric Shock

y p p1. Amount of current2. Path of the electricityy3. Duration of contact4. Voltage5. Resistance of human body 6. Frequency of the electrical supply7. Contact area of human body8. Conductivity of the surrounding environment

Electric ShockOccurs when touching the phase conductor andstanding on the ground

Electric Shock

standing on the ground

Y

PhaseB

R

N

Electric ShockBy touching a metallic part that has become live

Electric Shock

Y

METALLIC BODYB

N

R

N

T t t f l t i h kTreatment for electric shock

1. Don't touch the victim.2. Unplug or turn off the power3 If you can't turn off the power use a piece of wood3. If you can t turn off the power, use a piece of wood,

a broom handle to separate the victim from the power source.

4. Do not try to move a victim touching a high voltage wire. Call for emergency help.

5. Keep the victim lying down. Unconscious victims should be placed on their side to allow drainage of fl idfluids.

T t t f l t i h k6. Do not move the victim if there is a suspicion of

neck or spine injuries unless absolutely necessary

Treatment for electric shock

neck or spine injuries unless absolutely necessary.7. If the victim is not breathing, apply mouth-to-mouth

resuscitation If the victim has no pulse beginresuscitation. If the victim has no pulse, begincardiopulmonary resuscitation (CPR).

8 Then cover the victim with a blanket to maintain8. Then cover the victim with a blanket to maintainbody heat, keep the victim's head low and getmedical attention.

T t t f l t i h k7. The Cardiopulmonary Resuscitation (CPR) should

b i b Fi t Aid

Treatment for electric shock

be given by a First Aider.

ArcingArcingElectricity of sufficient pressure (Voltage) can jump an airgap Causing shock effects to persons not actually ingap. Causing shock effects to persons not actually incontact with a conductor. When a conductor carriessufficient potential to jump across an insulationmaterial (usually) arcing occursmaterial (usually) arcing occurs

Electrical Fire & Explosion:Electrical Fire & Explosion:Electric flow through a conductor generatesunsuitable conductor the excessive heatunsuitable conductor the excessive heatcaused can lead to fires. Also electricityeven at low current or voltages can igniteflammable heat. If a large flow passesthrough an gases, dusts or vapours.

Major Causes:1 Overloading of circuits1. Overloading of circuits2. Sub-standard material3. Improperly rated fuse4. Poor/damaged insulation5. Poor connections6. Flammable material near electrical

equipment.

El t i l BElectrical BurnIt can happen mainly in two ways1. When the body comes on the way

to electric arc / flash and2 When body acts as a conductor and2. When body acts as a conductor and

due to the heat generated the cells get burnt.g

Protective DevicesFuses: Fuses come with a current ratingand in case the amount of current exceeds

Protective Devices

the specified limits it melts to disconnectthe electricity flow and provide protection.Above mentioned formula for heat isAbove-mentioned formula for heat isapplicable here.Circuit Breakers: Circuit breakers areCircuit Breakers: Circuit breakers areelectromagnetic devices which perform thesame functions as fuses although theyoperate fasteroperate faster.Earthing: Electricity will always try to reachearth and earthing is a means of providingg p ga low resistance path to earth.

Protective DevicesIsolation: This means shutting off theelectrical supply to an item of equipment or

Protective Devices

pp y q ppart of an electrical system and preventingthe system from being mistakenlyreconnected and is used for example duringreconnected and is used for example duringmaintenance work.

R d d L V ltReduced Low Voltage:

Low voltage systems afford safety byreducing the mains voltage by means of areducing the mains voltage by means of atransformer to a lower safer voltagetypically 110 or 55volts and is used onconstruction sites etc.

Protective DevicesResidual Current Circuit Breakers (RCCB):Residual current circuit breakers provide protection against

Protective Devices

Residual current circuit-breakers provide protection againstleakage to earth and consequential risk of shock bycomparing the electricity flow to the equipment with thep g y q preturn flow along the neutral wire. If any difference isdetected the equipment is isolated.

Protective DevicesResidual Current Devices (RCD): an

l t i l d i hi h t t

Protective Devices

electrical device which protectspersonnel by detecting potentiallyhazardous leakage current and quicklyhazardous leakage current and quicklydisconnecting power from the circuit.

Double Insulation: Two separatelayers of insulation are provided whichallows for fault detection where oneallows for fault detection where onelayer has failed the other still providesprotection

Permit SystemPermit SystemLock Out & Tag Out Procedure (LOTO)

W ki d O h d LiWorking under Overhead Line1. Avoid working under OHL2 Obtain shutdown for the OHL2. Obtain shutdown for the OHL. 3. Establish Work permit system 4. Ensure minimum distance to be away from OHL is y

maintained 5. Have a chain fixed to thearms of the equipment toprevent accidentalprevent accidentalmovement of its armtowards the OHL

6 Post a Supervisor6. Post a Supervisor7. Inform the safe working

method8 E t t b8. Emergency steps to be

taken

W ki d O h d Li1. Detect the location of cable

Working under Overhead Line

2. Obtain shutdown3. Establish Work permit system 4. Do manual excavation5. Mechanical excavation is

hibit dprohibited6. Post a Supervisor7 I f th f ki th d7. Inform the safe working method8. Emergency steps to be taken9 Use insulated crow bars rubber9. Use insulated crow bars, rubber

shoes

Checklist to ensure electrical safety:1. Reduced voltage operation2. Use of residual current circuit breakers

Checklist to ensure electrical safety:

2. Use of residual current circuit breakers3. Apparatus and cables should be protected against overload by

fuses and/or circuit breakers4. All cables should be insulated and protected against mechanical p g

damage5. Correct types of sheathing to suit working conditions6. Sufficient socket outlets to minimise the need for trailing cables7. The use of cable drums wherever possible8. Correct maintenance and repair9. Correct connections10. Reduced voltage operation11. Use of residual current circuit breakers12. Regular inspections and checks to remove damaged equipment13. Properly trained operators

P t bl T l S f tPortable Tool - SafetyPlug1. Supply is taken through proper

fuse.2. Power supply to the electric tool is

thorough ELCB / RCD.3 No damage to plug casing3. No damage to plug casing.4. Proper wiring is given5 Earthing is given5. Earthing is given.

P t bl T l S f tCable1 Cable do not present a tripping hazard

Portable Tool - Safety

1. Cable do not present a tripping hazard.2. Never pull cord to disconnect.3. Being run over by vehicles.3. Being run over by vehicles.4. Being dragged over rough surfaces.5. Becoming trapped in doors or

machinery.6. Coming into contact with hot surfaces

or corrosive chemicals and solventsor corrosive chemicals and solvents.7. Continuous flexing (especially close to

the appliance).8. Do not carry the power tool by the cord.

P t bl T l S f tJoint & Connections

Portable Tool - Safety

1. No makeshift connections2. Loose connections.3 Connections ired incorrectl3. Connections wired incorrectly 4. Connection exposes bare wire 5 Poor earthing or no earth5. Poor earthing or no earth6. Overrated fuse Staggered joint

CABLE 13/4” 3/4” 3/4” 3/4”

CABLE 2

P t bl T l S f tAppliances:Portable Tool - Safety

1. Casing is not damaged2. There is no worn out connection.

Usages:Usages:1. Operate electric tools within their design limitations.2. Disconnect power when not in use.3 E th t it d t t t id t ll3. Ensure that it do not start accidentally.4. Do not use electric tools in damp or wet locations

unless they are approved for that purpose.5 K k ll li ht d h ti l t i5. Keep work areas well lighted when operating electric

tools.6. Store electric tools in a dry place when not in use.7 U l d i t f t f t h7. Use gloves and appropriate safety footwear when

using electric tools.

P t bl T l S f tInspection:

Portable Tool - Safety

1. Inspect any damage prior to each use.2. Check the handle and body casing for damage.3. If the tool has auxiliary or double handles, check

to see that they installed securely.4 Inspect cords for defects4. Inspect cords for defects5. Check for damaged switches and ones with

faulty trigger locks.faulty trigger locks.6. Inspect the plug for cracks and for missing,

loose or faulty prongs.

P t bl T l S f tReason for keeping inspection record:

Portable Tool - Safety

1. Whether the machine is inspected by an authorized person.

2. In case the test label is removed the record would help to identify.

3 To ensure the inspection and test are done as per3. To ensure the inspection and test are done as per schedule.

4. History of the records helps to assess the machine4. History of the records helps to assess the machine condition.

P t bl T l Ch kli tPortable Tool - Checklist

Power tool CheckPower tool Check list

El t i l S f t i Offi E i tElectrical Safety in Office Environments1. Are the equipment is of approved

standard2. Maintenance of fixed electrical

installations doneinstallations done3. Is there a means of isolation 4 Are all connections wiring free from4. Are all connections, wiring free from

damage5. Are correct fuses fixed5. Are correct fuses fixed6. Are plug correctly wired

El t i l S f t i Offi E i t7. Avoid overloading of outlets

Electrical Safety in Office Environments

8. Switch off appliances when not in use

9. Maintain good housekeeping10. Proper earthing given

R ti f C bl11. Routing of Cables12. RCDs are used13 S t f ti d f t13. System for reporting defects

Any QuestionsAny Questions