S.Mukhopadhyay

10.09.15Unrestricted

Electrical safety

�A report says that

every year 5500

Indians die due to

electric shock and

800 due to electric 800 due to electric

fire.

� 12% work place death

due to electrocution

There are four main types of electrical injuries:

Direct:

� Electrocution or death due to electrical shock

ELECTRICAL ACCIDENT

� Electrical shock

� Burns

Indirect

� Falls

ELECTRIC BURN

ELECTRIC BURN

ELECTRIC BURN

ELECTRIC BURN

ELECTRIC BURN

ELECTRIC BURN

ELECTRIC BURN

ELECTRIC BURN

ELECTRIC BURN

1. Severity of the shock depends

on:

� Path of current through the

body

Severity of shock

body

� Amount of current flowing

through the body

� Duration of the shocking

current through the body,

2. LOW VOLTAGE DOES NOT

MEAN LOW HAZARD

Causes burn Injuries

Causes death

LOW VOLTAGE CAN BE

HAZARDOUS

� A person feels electric shock when a current

passes through his body.

� It occurs when the human body becomes the part

Electric shock:

� It occurs when the human body becomes the part

of the electric current and completes the circuit

for the flow of electric current through it.

� The condition is that current must enter the body

at one point and leave at the other.

� Most dangerous path – Right hand to Left leg

The Indian Electricity Rules – 1956

Clearance from structures / sheds/ buildings to Low and Medium Voltage

Lines and Service lines

1. When the line passes over the building, provide a vertical clearance of 2.5m

[8 ft.] from the highest point of the roof, open balcony and verandah of the

building.

2. When the line passes adjacent to the building, provide a horizontal clearance of

1.2m [4 ft.] from the nearest point of roof, open balcony and verandah of building.1.2m [4 ft.] from the nearest point of roof, open balcony and verandah of building.

Clearance from structures / sheds/ buildings to High and Extra High Voltage

Line.

1. Provide a vertical clearance of 3.6m [12 ft.] upto 33KV and 3.6m [12 ft.] plus

0.3m [1 ft.] for every additional 33KV above the highest part of the building

immediately under such lines.

2. Provide a horizontal clearance of 1.2m [4 ft.] upto 11KV, 1.8m [6 ft.] upto 33KV

and1.8m [6 ft.] plus 0.3m [1 ft.] for every additional 33KV or part thereof, between

the nearest conductor and any part of the building.

Rule – 79 ,The Indian Electricity Rules- 1956

Magnitude of theCurrent

The effect on an adult (weight68 Kg)

From 0 to 0.5 mA no sensation

1 mA Threshold of perception

From 1 to 3mA weak sensation

From 3 to 10 mA Painful sensation

10 mA Threshold of muscular

ELECTRIC SHOCK

10 mA Threshold of muscularcontraction in the arms

30 mA Threshold of respiratoryparalysis

75 mA to 100 mA Threshold of cardiac fibrillation(probability 0.5%)

250 mA Cardiac fibrillation with 99.5%probability (for an exposure timeof 5 seconds)

4A Threshold of cardiac paralysis(sudden stoppage of the heart)

5A Burning of organic tissues

The electrical resistance of the human body varies widelyaccording to the age and sex of the individual.

RESISTANCE OF HUMAN BODY

Body area Resistance in Ohms

Dry skin 100,000 to 600,000 Dry skin 100,000 to 600,000

Wet skin 1000

Internal body hand to foot 400 to 600

Ear to Ear About 100

METAL 10 TO 50 Ohms

DRY SKIN 100,000 TO 600,000 Ohms

ELECTRICAL RESISTANCE

WOOD 100,000,000 Ohms

RUBBER 100,000,000,000,000 Ohms

Voltage category

LOW – upto - 250 VoltsMEDIUM- upto- 650 VoltsHIGH- upto - 33000 Volts

The Indian Electricity Rules – 1956

HIGH- upto - 33000 VoltsEXTRA HIGH- above - 33000 Volts

(as per Rule 2au of The Indian Electricity Rules -1956)

Current Calculation

I = V / R ( Ohms Law )

Say,

Voltage = 110 Volts ,

Resistance (R) = 1000 Ohms ,Resistance (R) = 1000 Ohms ,

then

Current (I) = 110 /1000

= 0.11 Amps

= 110 mA

Go Always for the best

� While procuring electrical items don’t compromise on

safety and quality.

ELECTRICAL SAFETY

� Always go for the best and use ISI / CE etc,marked

electrical items. These ensure that the products are

manufactured as per the laid down standards.

� It is the matter of your own safety

Earthing – the life saving specialist.

� The objective of an earthling system is to provide as early as possible

easy path for the flow of current to the ground in case of any fault in

the system.

ELECTRICAL SAFETY

� Avoiding the risk of current flow through the human body in case of

accidental contact takes place.

� If the leakage is considerably high it will blow off the backup fuses or

trip off circuit breakers.

� Earthing should be provided as per IS 3043 - 1987

Electrical Safety

ELCB or RCCB

� The earth leakage circuit breakers (ELCB) are the protection devicesagainst potential electric shock or fire.

� They operate on the current balance principle and trip off the circuitimmediately whenever a person comes in direct or indirect contact with

ELECTRICAL SAFETY

immediately whenever a person comes in direct or indirect contact withelectrical circuit thereby protecting human life or the possibility of fires.

� Rule 47(6) –The Building and other construction workers (Regulationand condition of service ) central Rules - 1998

“The employer shall ensure that all temporary electrical installations atbuilding or other construction work are provided with ELCB or RCCB.

ELCB

� 30mA ELCB offer highest degree of protection to human life against direct or indirect contact with live parts and electrical shock.

ELECTRICAL SAFETY

�ELCB should be selected for a rated current of approximately 15-20% more than the load the ELCB required to carry.

Safety in use Portable Tools

& appliances

1. Inspect portable tools and appliances and cords regular basis.

2. Use tagging system for good and damaged power tools

3. Use metal clad plug tops.4. Check the earthing connection is properly

connected connected

1. Do not remove plug by pulling cords 2. Don’t carry a tool by the cord3. Do not insert wires in socket always use

plug top .4. All cable joints of extension cables should

be insulated adequately5. Keep cable 2 meters above the ground.

Preventing Electrical

Hazards - Tools

1. Use Double Insulated power tools

2. Use insulated screwdriver

3. Insulated tools

Double

Insulated

marking

4. Insulated handling equipment If

equipment comes into contact with

energized parts

5. Protective shields, Barriers, Insulating

materials

Preventing Electrical

Hazards - Tools

Hazard – during Use

Hazard – during Use

Hazards - Temporary

Lights

1. Protect from contact and damage,

2. Don’t suspend by cords

Temporary Lights - Hand Lamp

Good Gesture

Good Gesture

Safety-Related Work

Practices

Barrier protection from electrical shock:

1. Use barriers and guards to prevent passage through areas of exposed energized through areas of exposed energized equipment

2. Warning signage

3. Keep working spaces and walkways clear of cords

Arc Flash

ARC-FLASH

• As much as 80% of all electrical injuries

are burns resulting from an arc-flash

and ignition of flammable clothing.

• Arc temperature can reach 35,000°F -• Arc temperature can reach 35,000°F -

this is four times hotter than the surface

of the sun

Fatal burns can occur at distances over

10 ft.

ARC EXPOSURE ENERGY

1. Exposure Energy is Expressed in cal/cm2

2. 1 Cal/cm2 Equals the Exposure on the tip of a

finger by a Cigarette Lighter in One Second.finger by a Cigarette Lighter in One Second.

3. An Exposure Energy of Only One or 2 Cal/cm2

Will Cause a 2nd Degree Burn on Human Skin.

Personal Protective Equipments (PPE)

Arc Flash - Personal Protective

Equipment

1. Hard Hat –(Electrical) Class E.

2. High voltage Rubber Gloves

3. Safety shoe (non conductive)

4. Testing and Maintaining

GlovesGloves

If possible to prevent damage

to rubber glove, protective

outer glove can be used

(leather glove)

Note: Leather gloves alone are not

recommended.

Arc Flash - Personal Protective

Equipment

Class Of Gloves: IS:4770 / 1991

(1) 650 Volts - Type 1(1) 650 Volts - Type 1

(2) 1100 Volts - Type 2

(3) 7500 Volts - Type 3

(4) 17,000 Volts - Type 4

Arc Flash - Personal Protective

Equipment

Face Shield - electric arcs,

flashes resulting from electrical

explosion.

Thermography

Infrared Thermography :-

Is used to perform inspections on electrical equipment.

Loose connections, overloaded or imbalanced of circuits causes resistance on electrical apparatus ultimately leads to electrical fault.fault.

Faulty breakers, damaged switches, faulty fuses and a wide range of other unwanted electrical conditions can be detected before the electrical component burns up.

Thermography is used to see the excess heat (resistance) so that problems can be found and maintenance personnel can act to correct the problem before the component fails, causing damage to the component, safety hazards and/or production downtime

Thermography

Stop Electrical

FIRE

Transmission line work

Transmission line work

High voltage detecting tester

Transmission line work

Discharge rod

Lockout and Tagging of

Circuits

� Apply locks to power source after de-energizing

� Tag deactivated controls

� Tag de-energized equipment and circuits at

all points where they can be energized

� Tags must identify equipment or circuits being

worked on

Electric Fire

� Switch off the power to the affected area.

� No water to be used for extinguishing electrical fires.

� For putting out electrical fires C02 or Dry Chemical Powder

(DCP) can be used or dry sand if available.(DCP) can be used or dry sand if available.

CPR

Unqualified Persons

Those people with little or

no training in avoiding

electrical hazards while

working on or near exposed

energized parts.

Thank you