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Indian regulations
in
Electrical Safety
P.Lahiri
BARC
1
Indian regulations.
• Indian Electricity Act-1910.
• Indian Electricity (Supply)
Act- 1948.
• Indian Electricity Regulatory
Commission Act-1998.
• The Electricity Act –2003.
Repealed
under section
185 of
Electricity act
-2003
• Indian Electricity Rules- 1956.
2
Objectives of regulations
• Make generation, transmission, distribution
and utilization of electricity as safe as
possible.
• Identification of different categories of
agencies.
• Remove ambiguities from existing
qualitative guidelines and pronounce precise
quantitative technical requirement with
respect to safety.
3
Categories of agencies
•
•
•
•
•
Supplier of electricity.
Consumer of electricity.
Electrical inspector.
Electrical contractor and supervisors.
Authorized persons.
4
Hazards of electricity
• Electric shock:- Current flows through body or part of body
when two surfaces having electrical potential difference is
touched resulting in burn, disability or even death.
• Flashover:-Sudden collapse of electric field by having a
conducting path between two electrical potential different
surfaces resulting in burn, fire.
• Blast:-Failure of dielectric medium between two electrical
potential different surfaces resulting in projectile, mechanical
force, fire or burn.
• Heat:-Caused by loose connection in the circuit, overheating of
insulation/ conductor due to overload or prolonged short circuit
current etc. resulting in fire, burn.
5
Quantitative effect of electric current
(up to 3sec.) on human (source Daziel)
Effect
mA
d.c
M
F
Perception threshold 5.2 3.5
Shock but not painful 9
6
Muscular control lost, 90 60
breathing difficulty.
Ventricular fibrillation 500 500
a.c
60Hz
M F
1.1 0.7
1.8 1.2
23 15
10kHz
M F
12 8
17 11
94 63
100 100
6
Flash and flame burn
Thermal burns, Current flows typically
external, Damage to skin
7
Electric shock and flash burn
8
Occurrence of blast
EXPLOSION
9
Classification of rated voltage as per IE rule
Above 33kV
Extra High Voltage (EHV)
33kV
High Voltage (HV)
650V
250V
Medium Voltage (MV)
Low Voltage (LV)
10
Authorization
• Authorization.
•
•
•
•
•
•
•
•
•
•
Electrical isolation.
Identification & display.
Restriction of access.
Inspection, testing etc.
Preparedness for adversity.
Other hazard precaution.
Protection & interlocks.
Clearances.
Earthing.
Reporting accidents.
• Avoid chaos
• Fixing up of
responsibility
• Ensures expertise
11
Authorization rule
Requirement
Applicable for
Rule
Work to be executed by
licensed electrical
contractor.
All new, addition,
alteration jobs having
electrical scope except
minor jobs.
Electrical installation
with more than 250kW
connected load
45(1),
(3)
Safety officer to be
authorized by owner with
approval of electrical
inspector.
Prior approval from
Any electrical work on
electrical inspector to work live apparatus/ line
3, 4,
5, 6
36
(2)
12
Authorization cntd.
Qualifications rule
Agency
Minimum
qualification
Rule
Authorized O & M person
for generating station of
capacity above 100MW
and sub-stations of 132kV
and above.
Second class
diploma in
mechanical or
electrical engineering
& training from CEA
approved institute.
ITI & training from
CEA approved
institute
3
(2A)
Assistants to above
3
(2A)
13
Electrical isolation.
• Authorization.
• Electrical isolation.
•
•
•
•
•
•
•
•
•
Identification & display.
Restriction of access.
Inspection, testing etc.
Preparedness for
adversity.
Other hazard precaution.
Protection & interlocks.
Clearances.
Earthing.
Reporting accidents.
• Quick de-energization
• Ensure de-energization
while on work
14
Electrical isolation(Rule)
Rating of service connection
Isolation
device
CB SFU
Rule
LV, MV service connection


upto 1000kVA at 11kV


Above 1000kVA at 11kV


50(b)
(i)
(ii)
upto 2500kVA at 33kV


Above 2500kVA at 33kV




*
Any rating beyond 33kV
15
LV,MV
16
11k,33k
or
17
>33k
18
Electrical isolation device for
transformers (Rule)
Rating of transformer
Isolation device
Pri:
Sec:
CB SFU CB SFU
*
*
Upto 630kVA and primary side
less than HV




upto 630kVA and primary side
HV and above.




630kVA to 1000kVA irrespective 
of primary voltage



Above 1000kVA irrespective of 



primary voltage
Rul
e
50(b)
(i)
(ii)
19
Above 1000kVA
20
Primary HV
21
630kVA
22
Identification & display
• Authorization.
• Electrical isolation.
• Electricity is invisible:-
–
–
–
• Restriction of access.
–
• Inspection, testing etc.
• Preparedness for adversity. –
• Identification &
display.
•
•
•
•
•
Other hazard precaution.
Protection & interlocks.
Clearances.
Earthing.
Reporting accidents.
Various current carrying portions
Different circuits/ phases/ a.c/ d.c. etc.
Different voltages LV,HV,MV etc
Power flow directions.
ON/OFF positions and direction of
operation of SFUs/CBs/Isolators.
– Source locations of PCCs/ MCCs and
load locations of each feeders of MCCs
– Danger notices.
23
Identification & display (Rule)
Requirement
Applicable for
Rule
Display of danger
notice.
Electrical installation
rated MV and above.
35
Visual identification All conductors
32(1)
by distinct colour.
connected to earthing
system
Visual distinction of All electrical installation 41
circuits, voltages,
feeders etc.
24
Restriction of access
• Authorization.
• Electrical isolation.
• Identification & display.
• Restriction of
access.
• Thwart accidental or
unauthorized access:-
• Inspection, testing etc.
• Preparedness for
adversity.
• Other hazard precaution.
• Protection & interlocks.
• Clearances.
• Earthing.
• Reporting accidents.
25
Restriction of access (Rule)
Requirement
Applicable for
Metallic covering
All live conductors for
which is electrically indoor installations.
and mechanically
continuous
Metallic fencing of Out door sub-station.
height not less than
1.8M.
Rule
51(1)
(a)
68(b)
26
Inspection testing & maintenance
•
•
•
•
Authorization.
Electrical isolation.
Identification & display.
Restriction of access.
• Inspection, testing
etc.
•
•
•
•
•
•
Preparedness for adversity.
Other hazard precaution.
Protection & interlocks.
Clearances.
Earthing.
Reporting accidents.
• Ensure adequacy of safety
related parameter:
• Maintaining safety related
parameter within limit.
27
Commissioning inspection (Rule)
Type of
Installation
Any
installation
upto MV (not
generating
plant)
Generating
plant of
capacity less
than 10kW
Type of test (Rule do not
specify) interpreted.
Visual inspection.
Insulation resistance.
High voltage.
Earth resistance.
Any functional requirement.
Same as above
Inspecting
authority
Supplier.
Owner
28
Commissioning inspection (Rule)
cntd.
Type of
Installation
Generating
plant of
capacity more
than 10kW
HV or EHV
installation
Type of test (Rule do not
specify) interpreted.
Depending upon voltage
level as desired by Electrical
Inspector
Inspecting
authority
Electrical
Inspector.
Visual inspection, insulation Electrical
resistance, high voltage,
Inspector.
earth resistance, functional
tests and test as desired by
29
Electrical Inspector.
Periodic inspection (Rule)
Type of test
Maximum
time interval.
Record keeping
duration
Test by inspector
5 years
Not specified
Earth resistance for 2 years
LV and MV
installation
2 years.
Earth resistance for 1 year
HV and EHV
installation
2 year
Fire extinguishers
Not specified
1 year
30
Preparedness.
•
•
•
•
•
Authorization.
Electrical isolation.
Identification & display.
Restriction of access.
Inspection, testing etc.
• Preparedness for
adversity.
•
•
•
•
•
• Mitigate the effect of fast
acting electrical disaster
• Ensure correct course of
action
Other hazard precaution.
Protection & interlocks.
Clearances.
Earthing.
Reporting accidents.
31
Preparedness (Rule)
Essential
Applicable for
Rule
First-aid
box,
Restoration
chart, Fire
buckets
Two or
more gas
masks
Every generating station,
enclosed sub-station and
enclosed switch station
43(2),
44(1),
43(1)
1.Generating station with
capacity of 5MW and above
2.Enclosed sub-station with
transformation capacity of 5
MVA and above
43(3)
32
Preparedness (Rule)
cntd.
Essential
Applicable for
Rule
Artificial
respirator
Every manned high voltage or 44(4)
extra-high voltage generating
station, sub-station or switch
station
Trained
All attended generating
44(3)
personnel for station and sub-station.
providing
artificial
respiration.
33
Possibility of success of artificial
respiration
source Edition Electric Institute resuscitation manual
34
Other hazard precaution.
•
•
•
•
•
•
Authorization.
Electrical isolation.
Identification & display.
Restriction of access.
Inspection, testing etc.
Preparedness for adversity.
• Other hazard
precaution.
•
•
•
•
• Reduce potential
initiating events of
accident
Protection & interlocks.
Clearances.
Earthing.
Reporting accidents.
35
Other hazard precaution.(Rule)
Situation
Safety measure
Rule
Electrical
installation in
explosive
atmosphere
Multistoried
building with
height more than
15M.
Explosion proof/ dust tight
depending upon the
hazardous zone as per
IS5571
1. Power cable ducts shall
not be used for other
services
2. Power cable ducts shall
have fire barrier at each
floor crossing
51(d)
50A(4)
36
Other hazard precaution.(Rule)
cntd..
Situation
Safety measure
Electrical
1.Baffle wall of 4hr fire rating
installation with between single phase banks
more than
and on consumer premise.
2000litres of oil 2.Oil soak pit for full quantity
of oil
Electrical
1.Measures mentioned above.
installation with 2.Fire extinguisher.
more than
3.Oil draining arrangement.
9000litres of oil
Rule
64(2)
-(e)
64(2)(e)
37
Other hazard precaution.(Rule)
cntd..
Situation
Safety measure
Substation 1.Entrance shall have 2hr fire rating
and switch
fire resistance door
station in 2.A curb at entrance to trap oil flow.
the
3.Direct access to transformer from
basement
outside
4.Transformer protection by
automatic HVWSp/ CO2/ BCF/
BTM/ N2 injection and drain.
Rule
64(2)
(f)(ii)
38
Other hazard precaution.(Rule) cntd..
Location based on oil inventory
Total oil
quantity in
litre (includes
Location
Rule
Indoor
Outdoor
Indl:
building
Res:/
com:
transformer and
other apparatus) 1st Gr. Other bldg. Any
Bs. Fl. floors floor of
No oil.
 



2000 or less
 



2000 to 9000





9000 or more





64
(2)
39
Protection & interlocks.
•
•
•
•
•
•
•
Authorization.
Electrical isolation.
Identification & display.
Restriction of access.
Inspection, testing etc.
Preparedness for adversity.
Other hazard precaution.
• Avoid human errors
• Protection &
interlocks.
• Clearances.
• Earthing.
• Reporting accidents.
40
Transformer protection
Rating
Less than 630kVA
and primary side
less than HV
Less than 630kVA
and primary side
more than HV
630kVA to
1000kVA
Mandatory relay
protection
No relay based
protection is
mandatory
Over current/ short
circuit relay etc for
secondary CB.
Over current/ short
circuit relay etc for
secondary CB.
Remark
Not specified
Not specified
but implied
by R50(b)(ii)
Not specified
but implied
by R50(b)(ii)
41
Transformer protection
cntd..
Rating
Mandatory relay
Remark
protection
1000kVA to 10MVA 1. Bucholz
R64(2)
2. Winding temp:
3. Oil temp:
More than 10MVA 1. Bucholz
R64(2)
2. Winding temp:
3. Oil temp:
4. Differential
42
HV & EHV installations interlocks
Situation
Preventive interlock
Isolator and CB in
series
Isolator operation not
allowed when CB is closed.
Earthing switch and
isolator
Earthing switch can not be
closed when isolator is
closed
Two or more incomer Only one feeder can be
feeders to a bus bar but switched on at a time
not intended for
parallel operation
Rule
64
(A)
(1)
43
HV & EHV installations interlocks
cntd..
Situation
Two or more
transformers in parallel
Preventive interlock
Rule
Secondary CB trips if
primary of that
transformer trips.
Doors or gates give
Doors can not be
64
access to live parts
opened when any part is
(A)
live.
(1)
Neutral switching device GCB can not be closed
between neutral and
when neutral breaker is
earthing is used for
open.
44
generator
HV & EHV installations protection
Protection
against.
Type of relay
Over current.
Over current/ short Any Equip., cable
circuit relay.
supply line etc.
Rising touch
potential.
Earth leakage/
earth fault.
Generator rated over
100kVA
Internal fault.
Differential relay
Generator rated over
1MVA Bus bars rated
over 200kV
Switching over Lightning arrestor
voltage/
lightning
Mandatory for
Overhead line
terminations
Rule
64A
(2)
92(1)
45
Other protections
Protection
for.
Human
safety.
Type of relay
Mandatory for
Rule
ELCB/ RCCB/
etc.
Any installation
having connected
load more than
5kW at MV or
above
DC three wire
system
61A
DC earthing. Over current
relay between
earthed middle
conductor and
earth.
61
(1)
(d)
(i)
46
Time/ Current for a.c 50Hz
mSec
50H a.c current (rms mA)
Zone 1- Usually no reaction, Zone 2 – Reaction may occur but
usually no patho- psychological dangerous effect, Zone 3- No risk of
fibrillation, Zone 4- Fibrillation possible (50% probability), Zone 5Unsafe or fibrillation
47
Clearances (physical spacing)
•
•
•
•
•
•
•
•
Authorization.
Electrical isolation.
Identification & display.
Restriction of access.
Inspection, testing etc.
Preparedness for adversity.
Other hazard precaution.
Protection & interlocks.
• Clearances.
• Minimum air insulation
clearance.
• Minimum space to work.
• Minimum space for
escape.
• Earthing.
• Reporting accidents.
48
Clearances for bare conductor other than
overhead lines(Rule)
Voltage
Section
clearance
(outdoor) in
m.m.
Upto 11kV 2600
Ground
Rule
clearance
(outdoor) in
m.m
2750
33kV
2800
3700
66kV
3000
4000
220kV
4300
5500
400kV
6500
8000
64
49
Clearance above ground of overhead lines
across/ along a street (Rule)
Condition
Across
Along
Any where
else
Every where
System voltage
Clearance in
mm
LV, MV
5800
HV
6100
LV, MV
5500
HV
5800
LV, MV, HV
(upto11kV)
4600
HV(above 11kV)
5200
EHV
5200 + 300 for
every 33kV but
not less than
6100
Rule
77
50
Clearance of overhead lines from
building(Rule)
Condition
Vertical
(IE R 79)
System voltage Minimum clearance in mm
LV, MV
2500
HV
3700
EHV
3700 + 300 for every 33kV
LV, MV
1200
HV upto 11kV
1200
Horizontal
(IE R 80) HV above
11kV
EHV
2000
2000 + 300 for every 33kV
51
Section clearance
SC
SC
SECTION CLEARANCE
52
Ground clearance
GC
Height of tall
man’s raised
finger tip with
raised hand2.5m
GROUND LEVEL
GROUND CLEARANCE
53
Earthing system.
•
•
•
•
•
•
•
•
•
Authorization.
Electrical isolation.
Identification & display.
Restriction of access.
Inspection, testing etc.
Preparedness for adversity.
Other hazard precaution.
Protection & interlocks.
Clearances.
• Earthing.
• Reporting accidents.
• Limit touch potential
• Limit step potential
• Safe predefined passage for
fault current
• Facilitate detection of
incipient fault
• Reduce neutral shifting
54
Step & Touch potential
Et
F
E/X CURVE
Es
E
Earth Mat
1M
0.5M
X
Earthing (Rule)
Requirement
Applicable for
Rule
Earthing terminal by
Supplier.
LV consumer
33
Separate earthing terminal
by supplier and consumer.
Minimum two independent
and redundant path with
two earth electrode.
All metallic part not
intended to serve as
conductor shall be earthed.
Grounding of neutral.
MV and above
33
Earthing network for
equipment, system. R61(2),
R61(3),
R51(1)(b),
All electrical
R67(1)
apparatus
a.c electrical power
supply system more
than 125V
61(1)(a),
64(3)
56
Reporting of accidents
•
•
•
•
•
•
•
•
•
•
Authorization.
Electrical isolation.
Identification & display.
Restriction of access.
Inspection, testing etc.
Preparedness for adversity.
Other hazard precaution.
Protection & interlocks.
Clearances.
Earthing.
• Reporting for analysis.
• Fast reporting prevents
suppression of facts.
• Reporting accidents.
57
Reporting of accidents (Rule)
Type of accident
Fatal involving loss
or injury
Failure of
transformer or
reactor above
20MVA
Report
format
Maximum Rule
period for
reporting
Telegraphic 24hours
44A
and
Written
48hours
Written
48hours
65(8)
58
Conclusion
• Regulations can induce more concern.
• Regulations can not rule out accidents by themselves
• Every concerned individuals should handle electricity in
safe manner
• Do not try to find out loopholes of regulation to limit our
responsibility.
• Try to adopt a proactive approach by understanding the
intentions of the regulation authors.
• In case of doubt ask electrical inspector or Central
Electricity Authority.
59
60
Clearance across the road
61
Clearance along the road
62
Clearance anywhere else
63
Clearance from building
Vertical clearance
Horizontal clearance
64
Fire barrier in cable duct
Fl-4
Cables
Fl-2
Fire
barrier
Fl-1
Electrical
service
shaft
65
Ground clearance for bare conductor
other than overhead lines(Rule)
Voltage
Clearance in mm
Outdoor
Upto
11kV
33kV
2750
66kV
4000
220kV
5500
400kV
8000
Height of tall
man’s raised
finger tip with
raised hand2.5m
3700
66
Phase to Phase(Rule)
Voltage
Clearance in mm Outdoor
Ph~Ph Ph~E Sec: Ground
11kV
33kV
66kV
220kV
400kV
460
915
1220
3350
4000
67
Phase to earth(Rule)
Voltage
11kV
33kV
66kV
220kV
400kV
Clearance in mm
Outdoor
305
610
750
1675
3500
68
Clearances
It denotes the minimum distance in air between two
potentially different points (this includes earthed/
ground surfaces) to avoid flashover during normal and
transient over voltage.
Phase to earth
Phase to earth
Minimum distance
between live
conducting parts and
neighboring earthed
parts.
69
Clearances
It denotes the minimum distance in air between two potentially
different points (this includes earthed/ ground surfaces) to avoid
flashover during normal and transient over voltage.
Phase to earth
Phase to phase
Phase to Phase
Minimum distance between
live parts of different phases.
70
Clearances
It denotes the minimum distance in air between two potentially
different points (this includes earthed/ ground surfaces) to avoid
flashover during normal and transient over voltage.
Phase to earth
Phase to Phase
Isolating clearance
Isolating clearance
Minimum distance
between two sides of
an open isolator
71
Clearances
It denotes the minimum distance in air between two potentially
different points (this includes earthed/ ground surfaces) to avoid
flashover during normal and transient over voltage.
Section clearance
Minimum distance
Phase to Phase
between maintenance zone
Isolating clearance and nearest live part plus
Section clearance one stretched arm length of
a person
Phase to earth
72
Clearances
It denotes the minimum distance in air between two potentially
different points (this includes earthed/ ground surfaces) to avoid
flashover during normal and transient over voltage.
Phase to earth
Phase to Phase
Isolating clearance
Section clearance
Ground clearance
Minimum distance
between lowest point of
support insulator and
ground
Ground clearance
73
Phase to earth & phase to phase
clearance
TOWER
GANTRY
PH-TO PH
PHASE
TO EARTH
CLEARANCES IN OUTDOOR
STRUCTURE
P-E rule
P-P rule
74
Isolating clearance
Isolating clearance
75
76
Safety provisions in IE Rules
• Authorization.
• Electrical isolation.
• Identification &
display.
• Restriction of
access.
• Inspection, testing
etc.
• Preparedness for
adversity.
• Other hazard
precaution.
• Protection &
interlocks.
• Clearances.
• Earthing.
• Reporting
accidents.
77
78