It is an notes on Electrical safety in industries

1. Module- 4
Electrical Safety

3. Electrical Safety - Introduction
• Electricity flows through some bodies easily than others. They offer little
resistance for flow of current. They are called conductors. Example – metals,
many liquids, surface or subsurface of earth etc.
• Other materials or substances generally slow or stop the flow of current and they
are called insulators. Example – glass, plastic, porcelain, clay, pottery, dry wood.
• Air is an insulator but can become conductor during an arc or lightening. Similarly
pure water is poor conductor but small impurities in water like salt, acid, solvents
or other materials can change water to conduct electricity.
• Similarly water can turn some insulators like wet wood, wet cotton etc. into
conductors
• Dry skin has a fairly high resistance to electric current. But when skin is wet or
moist it acts as a conductor.
• That means anyone working with electricity in damp or wet environment need to
exercise extra caution to prevent electrical hazards.
• However electricity has become part of our life both in domestic and industry
and hence utmost care to be taken while using electricity due to its inherent hazard

8. Electrical safety – Dangers of electricity
• Electric shocks resulting in burns, injury, deaths
• Electric flashovers resulting in deaths, fires, damages
• Electric faults resulting in arcing, explosions, and fires
• Explosions in electrical equipment resulting in damage to installations and deaths.
• Fire hazards resulting in destruction, loss of life and release of smoke. Dust, gases
which spread over large areas quickly.
• Pollution from power plants
• We are all aware of the above hazards related to electricity. Still we neglect many
aspects and tend to be careless while working with electrical apparatus. Careless
use of electricity is dangerous and leads to fires, shocks, destructions and deaths.
• Safety precautions are necessary and essential in design, manufacturing, testing,
transport, installation, operation and maintenance of electrical equipment and
installations. Safety precautions to be taken should be known understood by all
concerned personnel and should be documented as per statutory requirements as
well as checklist and do’s and don’ts.
• Safety Inspection is to be carried out at every stage right from design to operation
including maintenance.

11. Electrical safety – Provisions as per Indian Electricity rules 1956
1. Electric supply lines and apparatus shall be sufficient ratings, mechanical strength and
so constructed, installed, protected, worked and maintained to ensure safety of human
beings, animals and property. IS and NEC shall be followed(R 29)
2. Supplier and consumer both will take due precautions to avoid danger from service
lines and apparatus on consumers premises(R 30)
3.Suitable cut outs like fuse in fire proof receptacles shall be provided in every service
line (other than earth lines) at consumers premises (R 31)
4. Earth and neutral conductors shall be identified to distinguish from live conductor and
position of switches and cut out shall be safe (R 32)
5. Earth connection (terminal) shall be provided near the point of start of supply and the
consumer shall take steps to protect it from mechanical damage (R 33)
6. Bare conductors should be inaccessible with readily accessible switches to cut off
power supply (R 34)
7.Danger notice in Hindi, English or local language with a sign of skull and bones and the
words ‘Danger’ and ‘ ….Volts’ is necessary near medium and high voltage installation ie
above 250 V (R 35)

12. Electrical safety – Provisions as per Indian Electricity rules 1956
8. For the safety from supply lines and apparatus, earthing from lines, PPE to
workers (gloves, rubber shoes, safety belts, ladders, earthing devices, helmets, line
testers, form electrical and mechanical injury) and authorised working on live
lines are necessary (R 36)
9. Vehicle cut off switch (in operation) is a must in every electric vehicle, crane
etc. and the metal rails if any should be electrically continuous and earthed (R 37)
10. Insulating and Protective material of electric line should not be of material
that may produce noxious and hazardous gases on excessive heating (R 39)
11.Street boxes should be free from influx of water or gas and should be regularly
inspected. (R 40)
12. Different circuits should be distinguished from each other (R 41)
13. Voltage should not exceed the limits and AC-DC circuits should not come in
contact with each other when live (R 42)
14. Fire extinguishers for electric fire, fire buckets with clean dry sand, first aid
boxes, two or more gas masks, to be used in the event of a fire or smoke are
necessary (R 43)

13. Electrical safety – Provisions as per Indian Electricity rules 1956
15. Fatal accidents should be reported within 24 hours and non fatal within 48 hours (R
44A)
16. Electrical work should be carried out by a licensed electrical contractor under direct
supervision of a competent person and person holding permit by the State Govt.
Unauthorised work shall not be energised. (R 45)
17. Inspection of installation at every 5 years by the inspector (R 46)
18. (R 47 to 59) gives general conditions relating to supply and use of energy
19. (R 60 to 62) for low and medium voltages (upto 650 V) and ( R 63 to 73) for high
and extra high voltage provide for insulation resistance test, earth connection, ELCB,
testing operation and maintenance.
20. (R74 to 93) gives important safety clearances above ground and between conductors
and provision for material strength, stresses, joints, guarding, earthing, safety and
protective devices.
21. (R 94 to 108) is for traction and provides for voltage supply to vehicle, insulation of
lines, current density in rails, height of trolley wire etc.

14. Electrical safety – Provisions as per Indian Electricity rules 1956
22. (R 109 to 132) is regarding safety precautions while working in mines and oil
fields. They include plans, notices, lighting, communications, fire precautions,
earthing, protective equipments, voltage limits etc.
23. (R 133 to 142 gives relaxations and penalty provisions.

15. Electrical safety – OSHA standards on Electrical safety
• OSHA standards focuses on the design and use of electrical
equipment and systems.
• They cover only the exposed or operating elements such as
lighting equipment, motors, machines, appliances, switches,
controls and enclosures requiring that they be constructed and
installed to minimise work place electrical dangers.
• Also the standard mandates that an approved testing agency
to certify the electrical equipment before use in the workplace
to ensure it is safe.
• OSHA cover many electrical hazards in different industries.
OSHA electrical standards are based on National fire
protection association (NFPA) standard, National Electric
Code (NEC) and Electrical safety requirements for Employee
in work place.

16. Electrical safety – OSHA standards on Electrical safety
OSHA states two important basic points.
• First point is that live parts shall be de-energised before
working on or near them.
• Second point that even after the exposed parts have been de-
energised, they shall be treated as energised until LOTO
system is applied.
This can be achieved by following Process:
1. Determine all possible source of electrical supply to the
equipment referring to diagrams, drawings, and identification
tags.
2. After properly interrupting the load current open the
disconnecting devices if each source.
3. Where it is possible, visually inspect for disconnection
4. Apply LOTO system as per policy
5. Use voltage detector to test and verify they are de-energised
6. Where possibility of induced voltage or stored electrical energy
exists, ground the phase conductors.

17. Objectives of Safety and Security Measures
1.To establish Safety Management System and Safety Audit System
2.To achieve 100% safety and 100% security of Installations, equipment,
human life and animal life
3.To bring awareness about safety hazards and safety rules
4.To educate personnel
5.To understand cause and effect relationship in accidents and scientific
phenomena associated with electricity
6.To control the situations and prevent accidents, injury and loss to human
life, installations and property
7.To minimise loss in case of accident
8.To ensure prompt first aid and emergency help in case of accident
9.Study of unsafe acts and unsafe conditions leading to accidents and to take
corrective measures to eliminate them.

18. Hazards associated with Electricity
• Electricity is invisible and hence hazards are hidden and invisible.
The various types are hazards associated with electricity are:-
1. Electric shock due to direct contact with live wire/conductors while standing on earth or
while in contact with metallic earthed part.
2. Electric shock due to direct contact with non effectively earthed metal part carrying
leakage current or fault current or induced current
3. Electric shock and burn injuries due to flashovers from live part to the person in contact
with earth or earthed metallic part
4. Shocks due by capacitively charged electrical conductors disconnected from power circuit.
Eg. Capacitors, bus bars
5. Falling of persons from height due to shocks or flashovers while working on overhead
structures.
6. Falling of overhead parts such as conductors, hardware, structural on body
7. Falling of tools, objects, welding sparks etc
8. Explosion of oil filled equipment due to internal arcing (Transformers, Bushings, Circuit
Breakers etc)

19. Hazards associated with
Electricity
9. Fires caused by electric loose connections, electric arc, electric short circuits and electric
flashovers.
10.Release of poisonous liquids/gases. Release of Sulphur hexafluoride (SF6) gases from
circuit breakers during maintenance, release of synthetic fluids from capacitor cans.
11.Natural disasters such as lightning, strokes, earthquakes landslides.
12.Manmade disasters such as sabotage, bombing etc.
13.Short circuits caused by snakes, birds, rodents.
14.Explosions or accidents associated with high power rotating machines due to leakage of
cooling medium, failure of mechanical parts.
15.Injury due to contact with rotating parts of motors( fan, coupling) .
16.Sparks in electrical equipment installed in explosive atmosphere (mines).
17.Mechanical accidents due to failure of electrical controls, interlocks, protections,
machine or structural components.Vehicle Accident (Crane, Car, Lift etc)

20. Electrical safety – Hazards in Electrical installations and Apparatus
Sl No Incidence/condition Effect
1 Person touches live conductor or charged conductor Electric shock
2 Person touches faulted structure or any metal part Electric shock
3 Person touches faulted equipment enclosure Electric shock
4 Person places ladder or metal rod near live conductor Electric shock, flash over,
fault
5 Person carries metal rod/tool in clearance zone Electric shock, flash over,
fault
6 Person touches pre-charged capacitor or conductor Electric shock
7 Person using tool cuts insulation of live cable Electric shock, fault, fire
8 Person falls down from height injury
9 Person falls in trench, manhole injury
10 Explosion of porcelain enclosed equipment Injury, fire, oil filled
equipment destruction

21. Electrical safety – Hazards in Electrical installations and
Apparatus
Sl. No Incidence/Condition Effect
11 Explosion in oil filled power transformer Fire, Destruction, outage
12 Lightning strokes in tower, earth wire,
equipment
Flashover, failure
13 Rotating shafts/flanges without protection cover Accident
14 Unearthed rotating equipment body Shock
15 Loose contact leads to sparking, melting and
faults
Equipment failure and fault
16 Loose hardware in current circuit leads to
melting, faults, and fires
Equipment failure and fault
17 Faults in power cable due to overheat, insulation
failure, over voltage
Cable burst, fire, outage
18 Fault and fire in cable due to breaking of
conductor
Cable burst, fire, outage

22. Protection against Electrical Hazard
• Most Electrical accidents result from:
1. Unsafe Equipment or Installation
2. Unsafe Environment
3. Unsafe Work Practices
Some ways to prevent these accidents are through usage of insulation, guarding, grounding, electrical
protective devices and safe work practices.
Insulators such as glass, mica, rubber or plastic is used to coat the metals and other conductors help to stop
or reduce the flow of current. This prevents shocks, fire and short circuits. To be effective they should be
suitable for the voltage levels and conditions like temperature and environmental factors such as moisture, oil,
corrosive fumes or other factors which can cause failure of insulation.
Guarding involves locating or enclosing the electrical equipment to make sure people do not accidentally
come in contact with the live parts. Effective guarding requires equipment with exposed parts is accessible to
only authorised persons. Sturdy and permanent screens can also act as effective guards.
Conspicuous signs must be posted at the entrance to the electrical rooms and guarded locations to alert the
people to the electrical hazards and to forbid unauthorised entry. Signs like Danger, Warning, Caution, High
voltage etc to be exhibited.

23. Unsafe acts or Unsafe work practices include:
• Opening and closing of switches without authority, failure to place
warning signals wherever needed, operating the equipment without
proper knowledge.
• Working unsafely such as throwing tools, not maintaining proper
working space which is free from obstacles, good housekeeping etc
• Making safety devices inoperative
• Using unsafe equipment, wrong tools, or using hands instead of hand
tools.
• Distraction, ill health, disturbed state of mind
• Failure to use safe clothing, PPE
• Working in unsafe conditions
• Ignorance of potential hazard
• Sacrificing safety for the sake of speed and higher productivity
• Use of alcoholic beverages, mobile phones etc.

24. Electrical safety – Effect of electric current on human body
Electric shock occurs when the body becomes
part of the electric circuit. Shocks can occur in
three ways:
1. A person may come in contact with both the
conductors in a circuit
2. A person may provide a path between an ungrounded
conductor and ground.
3. A person may provide a path between the ground and a
conducting material that is in contact with a
ungrounded conductor.
• The extent of injury of shock depends upon three factors:
1. The amount of current conducted through the body
2. The path of the current through the body
3. The length of time a person is subjected to the current.

26. Electrical safety – Effect of electric current on human body
• The amount of current depends upon the potential difference
and the resistance. Effect of low current on the human body
ranges from mild tingling to death. An electric shock can
injure you in either or both the following
• A severe shock can stop the heart or the breathing muscles or
both
• The heating effects of current can cause severe burns
especially where the electricity enters and leaves the body.
• Other effects include severe bleeding, breathing difficulty
and ventricular fibrillation.

29. Why is low frequency current dangerous to the heart?
Because the heart beats at a fairly low frequency, low frequency current like the kind found in
modern day power systems (50Hz in India & 60Hz in North America) is very dangerous because it
can cause heart fibrillation.
The heart is made up of a group of muscles that all have to work together to pump the blood
through your body.
Heart fibrillation is the medical term for when these muscles are no longer working together: your
heart is off beat, and “flutters” or beats weakly but way faster than normal.
This weakly beating heart can’t pump blood through your body properly.
The blood won’t get to the lungs for oxygen, and the heart will quickly run out of oxygen and stop.
The is known as cardiac arrest, or a heart attack.

30. Electrical safety – Causes of Accidents
An accident is a sudden mishap that interrupts the operation of an activity. It
is unplanned and irreversible.
Electrical accidents could occur as follows:
1. Any person or animal coming in contact with snapped overhead conductor.
2. Any person or animal coming in contact with metallic line support, stay wire, unauthorised
energisation of fencing, electrical apparatus etc through which there is leakage of current due
to failure of insulation, damaged insulators etc.
3. Coming in contact with live overhead conductors during renewal of blown out fuses, replacing
street lamps, cutting across live underground cable or touching live overhead conductors with
metallic rods etc.
4. Climbing up poles, or towers and coming in contact with live overhead electrical conductors
maliciously, out of ignorance or with deliberate attempt to commit suicide.
5. Natural disasters leading to electrical accidents
6. Due to improper or defective equipment, failure to provide adequate PPE
7. The human factor

31. Electrical safety – Approaches to Prevent Accidents
• There can be more than one approach to prevent accidents and ensure
safety. Some of them are:-
1. Enforcements of Safety rules and Acts: In this approach the rules are
mandatory and no deviation is accepted and deviation will be viewed seriously
and punished. Dos and Don’ts are specified and enforced. Dos are always and
Don’s are never. People are made accountable for the Acts. Mandatory rules and
Laws regarding electrical safety are enforced on manufacturers, contractors,
Power supply companies and users.
2. Human Resource development approach: In this approach emphasis is on
training of every person for following safety principles. Special training is
organised periodically including on the job training in safety by seniors,
experienced persons and outside experts.
3. Psychological approach: Safety awareness is created in the workplace by
placing sign boards, display of drawings, displaying Dos and Don’ts, conducting
safety demonstrations, safety competitions and rewards for safe working.

32. Electrical safety – Approaches to Prevent Accidents
4.Safety Management approach: Management is committed for safety and
Accident prevention. Safety manager is appointed and safety systems are
established.
5.Engineering analysis approach: This emphasis is on cause and effect
relationship and multi cause analysis and determines the various methods to
eliminate the possible causes at the root. Engineering approach is very essential
in electrical safety
6.Total Quality Management approach: Safety is ensured by Quality
Assurance and Quality control at various stages including specifications, system
design, product design, manufacturing, testing, despatch, receipt, storage,
installations, commissioning, operation and maintenance and safety
management. TQM approach insists on quality excellence at every stage to
ensure 100 % safety. TQM correlates quality with safety and gives integrated
management approach for ensuring safety

33. Electrical safety – Prevention of shocks
• Apparatus/structures must be earthed
• Conductors should be insulated/enclosed/non accessible
• Persons should maintain safe clearances form H.V conductors
• Persons should wear safety insulating shoes and insulating hand gloves.
• Live line working should be avoided.
• Conductors should be touched only after making dead and discharged.

34. Electrical safety – Electric shocks
• Electric shock is a sudden stimulation of the nervous system of human
body by flow of current through a part of the body. Electric shocks are
life threatening situation. Shocks are caused by direct contact with live
conductor or a flashover.
• The severity of the shock depends upon the amount of current passing
through the body and the duration. The result of shock can be simple
annoying sensation to serious burn injuries to death within seconds.
• Primary shock is an electric shock of such magnitude that it may
produce direct physiological harm. The result of primary shocks are
Fibrillation ( irregular heart beat), respiratory tetanus (continuous
contraction of muscle).
• Secondary shock is of such magnitude that it will not produce direct
physiological harm, but it is annoying and may cause involuntary
muscle reaction. Result of secondary shocks are annoyance, alarm and
aversion, and loss of balance due to involuntary muscle reaction.

35. Electrical safety – Electric shocks
Electric shocks occur due to one or more of the following
situations:
• When part of the body bridges two phase wires by direct contact
• When part of the human body bridges one phase and earth, two phases
and earth by direct contact
• When part of the body bridges two points of the same phase which are
at different potential difference by direct contact.
• When part of the body touches two points having potential difference
across them. (due to supply voltage or induced voltage or charged
voltage
• Flash over involving part of human body

36. Electrical safety – Electric shocks
• The current flowing through the body Ib = Vb/Rb where Vb is Voltage across the
part of the body and Rb is the Resistance of the part of the body. ( in practice
value of current 10mA and above are in the shock range.
Body part Resistance Ohm
• Dry skin 10 – 50 Mega ohm
• Wet skin 1000 ohm
• Hand to foot (Excl. skin) 500 – 600 ohm
• Ear to Ear (Excl. skin) 100 ohm
• Dry skin is much safer than wet skin. Dry surrounding are safer than the wet
surrounding. Skin with perspiration has low resistance.
• Wet walls and wet insulation are dangerous
• Ear to ear shock is most dangerous. Hand to hand and hand to foot is very
dangerous. Shocks not involving heart, brain and involving only remote skin is
less dangerous. Skin with cuts and wounds, bruises has low resistance.

37. Electrical safety – Electric shocks
• Electric shocks may occur due to unsafe acts or unsafe conditions
associated with Electric work/installation.
• In practice following types of supply systems are most commonly
used:-
1. Three phase AC system with neutral earthed, either three wire
system or four wire system.
2. Bipolar DC system with neutral earthed, either three wire system
or two wire system. One pole is positive and other negative with
respect to earth.

38. Electrical safety – AC shocks versus DC shocks
• In shocks from AC currents of normal frequency, the shock current is sinusoidal with
frequency of 50 Hz.
• The mechanism of electric shocks is related to central nervous system in human body.
• The central nervous system controls the vital functions of the body by rhythmic control of
heart and lunge diaphragm by the brain.
• Under normal state, tiny cyclic signals flow from muscles to brain and vice versa through
central nervous system. These cyclic signals produce pumping of heart at the rate of 70-
80 cycles per minute and breathing by lungs at the rate of 12 to 16 cycles per minute.
These tiny periodic signals are in the range of few micro amps. These tiny signals give
muscles to contract or relax.
• Large external signals from shock current result in cramp of freeze of the muscles into
sudden contraction without giving time to relaxation
• Flow of AC electric current from external source in to the human body disturbs the
natural periodic electric signals in the body.
• Electric AC current currents flowing through the body are of the order of several milli
amps and they cause sudden contraction of muscles

39. Electrical safety – AC shocks versus DC shocks
• As a result, firstly the person touching the live conductor cannot
move his muscles and is unable to get detached (let- go)
• Secondly the muscles of lung diaphragm get contracted and the
functioning of the lungs gets adversely affected resulting in
irregular breathing or stoppage of breathing.
• Thirdly the various muscles of heart operating in synchronisation
with each other during normal state behave erratically during flow
of shock current through the body. Shock currents of certain
magnitude cause stoppage of heart resulting in stoppage of blood to
brain and victim dies within few seconds. This is called
Fibrillation.
• Normal frequency of heart beat is 70 cycles/min. AC supply has
frequency of 50 cycles/sec or 3000 cycles/min. Hence 50 cycle
current is very dangerous to lungs and heart.
• This does not happen in DC shock current. With DC current shocks
the disturbance in frequency of heart signals is only once. Hence
DC voltage levels produce the shock effects at higher voltage
values than the corresponding AC voltages

40. Electrical safety – Effect of Electric shocks on human body
Sl
No.
Effect Flow of Current Through Part of Body (mA)
AC 50 Hz AC 50
Hz
DC DC
Men Women Men Women
1 Slight sensation on hand 0.5 0.4 1 0.5
2 Perception threshold 1.4 0.7 5 3
3 Shock not painful, muscular control
not lost
1.8 1.5 9 6
4 Shock painful, muscular control not
lost
9 6 65 41
5 Shock painful, let go threshold 15 10 75 50
6 Shock painful, muscular
contractions, breathing difficulty
23 17 90 60 3 sec
7 Shock ventricular fibrillation,
breathing stops, death certain
100 100 500 500 10 sec

41. Electric safety – Safety precautions in small LV installations,
Residential buildings and shops
• Before carrying out repair work, switch off the main switch, take out the fuse
holders and keep it with you till the repair work is over.
• Use shock proof appliances.
• Use correct fuse wires
• Miniature circuit breakers are preferred.
• Do not use immersion water heaters, exposed room heaters
• Use good quality copper wires for wiring
• Replace worn out wiring
• Do not allow water leakages. Seepage in walls/over switch boards.
• Replace defective switches immediately
• While working on live wires, stand on a dry wooden stool, use insulated tools.
However it is better to switch off the mains during the repair.
• Ensure that earthing system is healthy. Provide secured three pin plug for
secured earthing of appliances

42. Electric safety – Safety procedures in a Electrical Power plant
• Procedures and paper work for the following should be enforced from the
beginning and continued while commissioning, operation and maintenance
of electrical installations:
• Permit to work
• Access to work
• Entry passes
• Material gate pass etc.
Safety : The installation, commissioning, operation and maintenance work should
be carried out with written permission of authorised person.

43. Electric safety – Safety procedures in a Electrical Power plant
Steps should be taken by concerned authorities to ensure safety. They include:
1. Isolation of the part from live parts during the period of installation, testing and maintenance. No
switching on by mistake.
2. Danger notices and safety notices should be place in work place
3. The neighbouring switches should be locked upon to avoid switching by a third person.
4. Proper tools , safety devices should be provided to the electricians.
1. Earthing: The work equipment and conductors should be isolated and then earthed by means of
earthing connections, from all ends /incomers/out goers
2. The electricians should be well trained.
3. First aid should be available
4. Make sure to switch off the supply from all ends. Switching on should be allowed after the
completion of work and after cancellation of the permit by the authority.
5. Follow the safety rules faithfully
6. Work as per the permit system of the company. Take a work permit before starting of any job and
return it to the authority after completion of the job.
7. The repair/maintenance work on HV line/apparatus should not be undertaken unless the apparatus
is made dead and isolators open and locked, earthing switches closed and locked. All HV conductors
should be discharged and connected securely to earth.
8. Use appropriate PPE
9. Do not use wet clothes, wet shoes and metal tapes.

44. Electric safety – Safety procedures in a Electrical Power plant
14.Barricade the area under maintenance to clearly indicate the maintenance
zone and safe zone
15. Earth the various metallic parts of structures, bus sections, conducting parts
etc at two or more places before commencing the work.
16. Be familiar with circuit and auxiliary supply circuits and switch off both.

45. Electric safety – Safety procedures in a Electrical Power plant
• Recommended precautions to be taken before working on HV lines/apparatus
1. Apparatus/parts are dead, isolated and earthed
2. Steps to be taken to lock off from other live conductors
3. Effectively earthed at all points of disconnections, of supply to such apparatus or
between such points and point of work.
4. All caution boards are to be displayed.
5. Barricading/screening of work area to prevent encroachment in unsafe zone.
6. Authorisation to work is obtained through work permit system. Following all
safety instructions, precautions and usage of safety devices/PPE as specified in
the Permit.
7. The work to be carried out by trained personnel in accordance with the rules.
8. Safety clearances between live system and other physical objects like ladders
platforms, lifting devices etc to be ensured before taking up/ while executing the
job.

46. 1. What are primary and secondary electric shocks? Discuss the effect of
electric current on human body. (08Marks)
2. Discuss various safety precautions to be taken in small and residential
building installations against electrical hazard. (08Marks)
3. Discuss the process of achieving electrically safe work conditions.
(08Marks)
4. Discuss various safety procedures and paper work to be enforced while
commissioning operation and maintenance of electrical installation in an
electrical plant. (08Marks)