This document provides an overview of electrical safety and risk assessment. It discusses common electrical hazards like electric shock, burns, fires and explosions. The key causes of electrical accidents are identified as drilling into electrical cables, using defective equipment, and failure to follow lockout/tagout procedures. Electrical safety measures discussed include proper wiring, use of circuit breakers and disconnects, guarding live parts, adequate illumination and headroom, and grounding/bonding principles. Personal protective equipment and safety signage are also addressed.

1. ELECTRICAL SAFETY
AND
RISK ASSESSMENT
Presented By:-
Ar. MOHAMMED AZMATULLAH
&
Ar. KASHIF RAFI
Guided By:-
Ar. Ali Ahmad Shah
M.Arch - Building Service, 2nd Year,
FACULTY OF ARCHITECTURE & EKISTICS - JAMIA MILLIA ISLAMIA
New Delhi, INDIA

2. INTRODUCTION
• Hazard means any potential or actual threat to the wellbeing of
people, machinery or environment.
• Electrical hazard safety means taking precautions to identify and
control electrical hazards
Failing to take the necessary precautions can lead to:
- injury or death
- fire or property damage
Electric shock is the effect produced on the body and
particularly on the nervous system by an electrical current
passing through it. The effect depends on the current strength
which itself depends on the voltage and body resistance

3. !!!...???

4. Common causes of electrocution are:
- Making contact with overhead wires
- Undertaking maintenance on live equipment
- Working with damaged electrical equipment - extension leads, plugs
and sockets
- Using equipment affected by rain or water ingress
Electrical hazards exist in almost every workplace.
Voltage Rating

5. • There are four main types of electrical injuries:
• Electrocution (death due to electrical shock)
• Electrical Shock
• Burns
• Falls
Electric shock is the passing of electric current
through the body.
Electrical contact can cause involuntary physical
movements. The electrical current may
• prevent you from releasing your grip
from a live conductor
• throw you into contact with a higher
voltage conductor
• cause you to lose your balance and fall
• cause severe internal and external burns
• kill you.
A major cause of accidents involving
electricity comes from the failure to identify
the hazards associated with live electrical
equipment and wiring.
One is by electric shock and the
other is by arc flash.
Electricity will take the path of least resistance.
Severity of the shock depends on:
 Path of current through the body
 Amount of current flowing
through the body
 Length of time the body is in the
circuit

6. Assessing electrical shock risk

7. The flash causes an explosive expansion of air and metal.
The blast produces
• A DANGEROUS PRESSURE WAVE
• A DANGEROUS SOUND WAVE
• SHRAPNEL
• EXTREME HEAT
• EXTREME LIGHT.
These dangers can result in blast injuries, lung
injuries, ruptured eardrums, shrapnel wounds,
severe burns, and blindness.
Arc flash injuries can also result in death.
ARC FLASH
An arc flash is a release of energy caused by an electric arc.
An arc flash happens when electric current flows through an air gap
between conductors.
ARC BLAST
• Arc-blasts occur from high- amperage currents arcing through the air.
This can be caused by accidental contact with energized components or equipment failure.

8. ELECTRICITY
CONDUCTOR
• Metals such as copper, silver, gold and aluminium.
• Loose electrons in abundance so charge can be transferred easily
INSULATOR
• Usually non-metallic such as wood, rubber, glass, etc
• Contains few free electrons
ELECTRIC CURRENT
• Caused by the motion of electrons
• If channeled in a given direction, a flow of electrons
occurs.
DIRECT CURRENT
• - Always flows in one direction
• - Used to charge batteries, run some motors, operate magnetic
• lifting devices and welding equipment.
ALTERNATING CURRENT
• - More common in electrical work
• - Changes rapidly in both direction and value

9. • Are the most common shock-related nonfatal
injury
• Occur when you touch electrical wiring or
equipment that is improperly used or maintained
EXPLOSION
Explosions occur when electricity provides a source of
ignition for an explosive mixture in the atmosphere.
ELECTRICAL BURN
FIRE
Electricity is one of the most common causes of fires
both in the home and in the workplace.
Defective or misused electrical equipment is a major
cause.
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10. ELECTRICAL ACCIDENTS - REASONS
1. Drilling and cutting through cables
2. Using defective tools, cables and equipment
3. Failure to de-energize circuits and follow Lockout/Tag out
procedures
4. Failure to guard live parts from accidental worker contact
5. Unqualified employees working with electricity
6. Improper installation/use of temporary electrical systems and
equipment
7. By-passing electrical protective devices.
8. Not using GFCI (ground fault circuit interrupters) devices
9. Missing ground prongs on extension cords

11. Nature and mechanism of electric shocks
• The nervous system of the human body controls all its movements, both
conscious and unconscious.
• The system carries electrical signals between the brain and the muscles,
which are thus stimulated into action
• The signals are electro-chemical in nature, with LEVELS OF A FEW
MILLIVOLTS, so when the human body becomes part of a much more
powerful external circuit, its normal operations are swamped by the outside
signals.
• The current forced through the nervous system of the body by external
voltage is electric shock.
• All the muscles affected receive much stronger signals than those they
normally get and operate very much more violently as a result.
• This causes uncontrolled movements and pain.
• Even a patient who is still conscious is usually quite unable to counter the
effects of the shock, because the signals from his brain, which try to offset
the effects of the shock currents, are lost in the strength of the imposed
signals.

12. • Each disconnecting means legibly marked to indicate its purpose.
• Switches and circuit breakers must be clearly labeled to indicate its
circuit’s function
WORKING SPACE
• Sufficient access and working space around all
electrical equipment, provided & maintained to
provide ready and safe operation and maintenance.
• Not used for storage
ELECTRICAL SAFETY MEASURES
DISCONNECTING MEANS AND CIRCUITS LABELLING
Circuit breaker for
Motors 1,2,3, and 4
Disconnect switch
For motor number 3
Overloaded circuits can cause fires.

13. • Illumination provided for all working spaces
• The minimum headroom of working spaces about
service equipment, switchboards, panel- boards, or
motor control centers shall be 6 feet 3 inches
• Live parts of electric equipment guarded against
accidental contact by approved cabinets or other
GUARDING LIVE PARTS
forms of approved enclosures, or by any of the following means:
(i) By location in a room, vault, accessible only to QUALIFIED
PERSONS
(ii) By permanent, substantial partitions or screens
(iii) By elevation of 8 feet or more above the floor or other working
surface
ILLUMINATION AND HEADROOM
Entrances to rooms and other guarded locations containing exposed live
parts shall be marked with conspicuous warning signs forbidding
unqualified persons to enter

14. WIRING DESIGN AND PROTECTION
• Proper colour codes prescribed for wiring should be used.
Sizing of Cable to make sure conductor temperature within permissible
limit.
Protection of Cable to protect from overload and short-circuit current
through it.
Selective property of low smoke, zero halogen and fire-retardant
During any fire incidence, cable performance is
always a subject of doubt and comes under
scrutiny by forensic department.
ADEQUATE WIRING SIZE
• A hazard exists when a conductor is too small to safely carry the current.
• Using a portable tool with an extension cord that has a wire too small for the tool.
• Tool draws more current than cord can handle, can result in overheating, possible
fire without tripping the circuit breaker
• A cable design consists of conductor, insulation, sheath, armor etc and a few more
items for special cables.

15. Defective or inadequate insulation is a hazard.
Insulation prevents conductors from contacting each other or you.
Never attempt to repair a damaged cord with
tape.
W I R I N G

16. • Means shall be provided to disconnect all
conductors in a building from the service-
entrance conductors.
• The disconnecting means shall plainly indicate
whether it is in the open or closed position and
shall be installed at a readily accessible location
nearest the point of entrance of the service-
entrance conductors.
CIRCUIT BREAKERS
AVOID OVERLOADING
• Too many devices plugged into circuit may result in wires heated to
very high temperature & possible fire
• Wire insulation melts may result in arcing & fire in area where
overload exists
The circuit breaker is an absolutely essential device in
the modern world, and one of the most important safety
mechanisms.
• Circuit breakers shall clearly indicate whether they are
in the open (off) or closed (on) position.
DISCONNECTING MEANS
Overloaded circuits can cause fires.

17. EARTHING/GROUNDING/BOUNDING
• Very important for safety
• Prevents conducting parts of equipment (ie. metal frames or lids),
which do not normally conduct electricity from becoming live
during faults.
• No bonding
• Person can receive an electric shock if equipment becomes faulty
• All equipment bonded together
• No potential (voltage) difference between live casing and handrail
• If case becomes live fuse should blow
A Bonding system connects various pieces of
conductive equipment together to keep them at the
same potential. Static sparking cannot take place
between objects that are the same potential.
Grounding is a special form of bonding in which
conductive equipment is connected to an earthing
electrode or to the building grounding system in
order to prevent sparking between conductive
equipment and grounded structures.
Grounding is normally a secondary protective measure to
protect against electric shock.

18. EARTHING
• In electricity supply systems, an earthing system or grounding system is circuitry which connects
parts of the electric circuit with the ground, thus defining the electric potentialof the conductors
relative to the Earth's conductive surface. The choice of earthing system can affect
the safety and electromagnetic compatibility of the power supply. In particular, it affects the
magnitude and distribution of short circuit currents through the system, and the effects it creates
on equipment and people in the proximity of the circuit. If a fault within an electrical device
connects a live supply conductor to an exposed conductive surface, anyone touching it while
electrically connected to the earth will complete a circuit back to the earthed supply conductor and
receive an electric shock.
People use an earthing system mainly for these applications:
• To protect a structure from lightning strike, directing the lightning through the earthing system and
into the ground rod rather than passing through the structure.
• Part of the safety system of mains electricity, preventing problems associated with floating
ground and sky voltage.
• The most common ground plane for large monopole antenna and some other kinds of radio
antenna.
• Other, less common applications of earthing systems include:
• single-wire earth return.
• part of a system that powers small devices from sky voltage.
• one at each end of a ground dipole ELF antenna.

19. TYPES OF EARTHING SYSTEM
"T" — Direct connection of a point with earth (Latin: terra)
"I" — No point is connected with earth (isolation), except perhaps via a high impedance.
The second letter indicates the connection between earth and the electrical device being
supplied:
"T" — Direct connection of a point with earth
"N" — Direct connection to neutral at the origin of installation, which is connected to the earth
TN networks
In a TN earthing system, one of the points in the
generator or transformer is connected with earth,
usually the star point in a three-phase system.
The body of the electrical device is connected with
earth via this earth connection at the transformer.
The conductor that connects the exposed metallic
parts of the consumer's electrical installation is called
protective earth (PE; see also: Ground).
The conductor that connects to the star point in a
three-phase system, or that carries the return current
in a single-phase system, is called neutral (N).
Three variants of TN systems are distinguished:

20. TYPES OF EARTHING SYSTEM
TN−S
PE and N are separate conductors that are connected together only near the power
source. This arrangement is a current standard for most residential and
industrial electric systems particularly in Europe.
TN−C
A combined PEN conductor fulfils the functions of both a PE and an N conductor.
Rarely used.
TN−C−S
Part of the system uses a combined PEN conductor, which is at some point split up
into separate PE and N lines. The combined PEN conductor typically occurs
between the substation and the entry point into the building, and separated in
the service head. In the UK, this system is also known as protective multiple
earthing (PME), because of the practice of connecting the combined neutral-
and-earth conductor to real earth at many locations, to reduce the risk of
electric shock in the event of a broken PEN conductor - with a similar system in
Australia and New Zealand being designated as multiple earthed neutral (MEN).

21. TYPES OF EARTHING SYSTEM
TN-S: separate protective
earth (PE) and neutral (N)
conductors from transformer
to consuming device, which
are not connected together
at any point after the
building distribution point.
TN-C: combined PE and N
conductor all the way from
the transformer to the
consuming device.
TN-C-S earthing system:
combined PEN conductor
from transformer to building
distribution point, but
separate PE and N
conductors in fixed indoor
wiring and flexible power
cords.
It is possible to have both TN-S and TN-C-S supplies taken from the same transformer. For
example, the sheaths on some underground cables corrode and stop providing good earth
connections, and so homes where "bad earths" are found may be converted to TN-C-S.

22. COMPARISON
TT IT TN-S TN-C TN-C-S
Earth fault loop
impedance
High Highest Low Low Low
RCD preferred? Yes N/A No No No
Need earth electrode at
site?
Yes Yes No No No
PE conductor cost Low Low Highest Least High
Risk of broken neutral No No High Highest High
Safety Safe Less Safe Safest Least Safe Safe
Electromagnetic
interference
Least Least Low High Low
Safety risks
High loop impedance
(step voltages)
Double fault,
overvoltage
Broken neutral Broken neutral Broken neutral
Advantages Safe and reliable
Continuity of operation,
cost
Safest Cost Safety and cost

24. Earthing and bonding principles and prevalent
practices. .
• Earthing and Bonding have often been confused as
being the same thing when in fact the two are quite
distinct from each other.
• A Bonding system connects various pieces of
conductive equipment together to keep them at the
same potential. Static sparking cannot take place
between objects that are the same potential.
• Grounding is a special form of bonding in which
conductive equipment is connected to an earthing
electrode or to the building grounding system in order
to prevent sparking between conductive equipment
and grounded structures.1

25. ENCLOSURE FOR DAMP OR WET LOCATION
• GFCIs are generally installed where
electrical circuits may accidentally come
into contact with water.
• They are most often found in kitchens,
bath and laundry rooms, or even out-of-
doors or in the garage where electric
power tools might be used.
What is a GFCI???
• Cabinets, cutouts boxes, fittings, and panel
boards shall be weatherproof.
• Switches, circuit breakers, and switchboards
shall be in weather proof enclosures.
• A ground-fault circuit interrupter (GFCI) can help prevent electrocution.
• If a person’s body starts to receive a shock, the GFCI senses this and cuts
off the power before he/she can get injured.

26. • Flexible cords and cables shall be protected from accidental damage.
• Sharp corners and projections shall be avoided.
• Where passing through doorways or other pinch points, flexible cords and cables shall be
provided with protection to avoid damage.
When conductor enters a box or cabinet, they must be
protected by some type of lock or rubber perforation
from the sharp edges of cabinets, boxes, or fittings
• All pull boxes, junction boxes and fittings must be
provided with approved covers
• If covers are metal they must be grounded.
BOXES & CABINETS
TEMPORARY WIRING

28. • Safety signs, safety symbols, or accident prevention tags shall
be used where necessary to warn employees about electrical
hazards
• Barricades shall be used in conjunction with safety signs
• If signs and barricades do not provide sufficient warning and
protection from electrical hazards, an attendant shall be
stationed to warn and protect employees
The following alerting techniques shall be used to warn and protect
living being from hazards which could cause injury due to electric
shock, burns, or failure of electric equipment parts:

29. FUSES AND RCD’s
FUSES
• Will cut off supply at a certain current level
• i.e. 13A, 5A, 3A mains supply fuse.
• Fuse has a ‘fusible’ wire element which heats
up when current flows.
• Excessive current = excessive heat & wire
• melts preventing current flow
RCD’s
• Residual current device
• Compares current in Live & Neutral,
• if different and above a certain value supply switched off
FUSE
HRC FUSES
MCB
MCCB
RCD
ELCB
OIL CIRCUIT BREAKER
GAS CIRCUIT BREAKER
VACCUM CIRCUIT BREAKER
RELAYS….
A circuit breaker is an automatically
operated electrical switch designed to protect
an electrical circuit from damage caused
byoverload or short circuit.

30. What is safety device of diesel generator?
• safety devices of generator depends on the type of prime mover
used in generator.
• The main safety devices in a DG Set is to control the over speed, to
limit the fuel supply in case of emergency.
• It is regulated by the governor of the DG Sets. In external safety, over
voltage & over current tripping relay i.e. associated with DG Sets
control panel.
• Some small control transformers have a built in primary fuse.
• Larger transformers are primary fused externally and pole
transformers are primary fused externally with the fuse holders
mounted on cross arms near the transformer.

31. Standards
Rating of Outlets:-
To be adopted for design:
1. Incandescent lamps in residential and non-residential buildings shall be rated at 60W and
100W respectively.
2. Ceiling fans shall be rated at 60W. Exhaust fans , fluorescent tubes, compact fluorescent
tubes, HPMV lamps, HSPV lamps etc, shall be rated according to their capacity. Control gear
loses shall be also considered as applicable.
3. 6A and 16A socket outlet points shall be rated at 100W and 1000W respectively, unless the
actual values of load are specified.
Capacity of circuits:
1. Lighting circuit shall feed light / fan. Call bell points. Each circuit shall not have more than
800W connected load or more than 10 points.
2. However, incase of CFL points where load per point may be less number of points may be
suitably increased.
2. Power circuit in non residential building will have only one outlet per circuit.
3. Each power circuit in residential building can feed following outlets :
a)Not more than 2 nos. 16A outlet
b)Not more thane 3nos. 6A
c) Not more than 1 No. 16A and 2 Nos. 6A outlets.
4. Load more than 1KW shall be controlled by suitably rated MCB and cable size shall be
decided as per calculation

32. copper conductor cable only will be used for sub main/circuit/point, wiring.
Minimum size of wiring
light Wiring: 1.5 Sq.mm.
Power Wiring: 4.0 Sq.mm.
Power circuit rated more than 1KW , size as per calculation.
Insulation:
copper conductor cable shall be PVC insulated, Fire retardant , low smoke (FRLS) type
conforming to BIS specification.
Multi Stranded : Cables are permitted to be used.
Standards
Cables:
light Wiring: 1.5 Sq.mm.
Unfortunately, there is no straightforward answer to this question. A cable's current-carrying capacity
depends on various factors, including: the number of cores, its type of insulation, whether it's armoured or
not, and the method of installation. Depending on these factors, the current-carrying capacity varies from
around 14 A to around 21 A, but for specific information, you'll need to check out the appropriate Tables
in BS7671:2008 Requirements for Electrical Installations.

33. How calculate current carrying capacity of 16 sq mm
copper wire?
• AS PER THUMB RULE THE CURRENT CARRYING
CAPACITY OF WIRE IS 4 TIMES OF ITS
CROSSECTIONAL AREA OF WIRE i.e. 10 sq.mm wire
carrying maximum current 40 amp , 16 sq.mm
carrying maximum current 64 amp ,
• now amp convert in watt by multiplying by volt i.e.
240
• 16 sq.mm carrying max load 64x240= 15360 watt

34. Rules
• Indian Electricity Rules, 2005 defines the basic fundamentals of Electricity Safety, and when
followed in totality there cannot be any incidence of electrocution or electric fire.
• General Safety requirements are given in Chapter IV under rules 29 to 46 which covers
installation, protection, operation, maintenance cut-out, identification of earth,
earthed terminal, danger notice etc.
• General Rule 29 covers installation shall be constructed, installed, protected, worked and
maintained in accordance with BIS. It further stipulates that the material and equipment
used shall conform to the relevant specifications of the BIS.
• The National Electrical Code issued by BIS states in Clause 3.1.3.6 that the current rating of a
fuse shall not exceed the current rating of the smallest cable in the circuit protected by the
fuse.
• Rule no 31 talks about protection of every line by a cut-out. A cut out is defined as any
appliance for automatically interrupting the transmission of energy through any conductor
when the current rises above the pre-determined amount and shall also include a fusible
cutout.
• Rule 45 speaks that only authorized person shall be permitted to carry out electricity work
who is licensed by the the Government.
• Rule No. 32 and 33 speaks about earthed terminal for the purpose that if the current leaks
out, it should not harm the being but get discharged to earth immediately.

35. Do’s and Don’ts for Electrical Safety – Home and general
public – 230V and HT supply
• 230V AC is house hold supply and can be dangerous.
• Ensure three pin plug socket, earth connection on appliance and wire
continuity and its resistance.
• Earth pin is thick for its ability to carry high fault current and long for it to touch
first before phase is connected.
• Ensure socket closure mechanism to prevent children entering their finger
inside
• Earth leakage current if not flowing through earth wire will find path through
damp wall and pipe line and may be fatal.
• Provide earth leakage detector(RCB) along with over current protection
(MCB)
• Be watch full if duty cycle of any socket is very high. There is possibility of
loose connection which may result overheating, smoke and even fire.
• Check LT over head line is protected by a guard wire
• Ensure HT supply in your area is properly fenced and impossible for children
to find entry

36. Worker end
• Use safety and testing tools – Rubber sole shoes, Helmet,
safety sling (working on HT line), Continuity tester,
• Switch off power supply, test personally and fix sticker ‘Men
at Work’
• Take permit to work when working on HT line
• Never keep any inflammable item near electrical installation
• Protect HT switching station from rodent/lizards etc.
• Ensure provision of danger board
• Fence the HT area from unauthorized entry of even animals.
• Never assume and always test to be certain

38. Area required for generator in electrical substation

39. • A good example is the 'no-let-go' effect. Here, a person touches a
conductor which sends shock currents through his hand. The
muscles respond by closing the fingers on the conductor, so it is
tightly grasped. The person wants to release the conductor, which is
causing pain, but the electrical signals from his brain are swamped
by the shock current and he is unable to let go of the offending
conductor.
• The effects of an electric shock vary considerably depending on the
current imposed on the nervous system, and the path taken
through the body. The subject is very complex but it has become
clear that the damage done to the human body depends on two
factors:
• 1. - the value of shock current flowing, and
2. - the time for which it flows.

40. References
• tlc-direct.co.uk/Book
• NBC
• IEEE
• BIS
• Electrical Safety Hand book
• Electrical Hazard General
Thanks