Indian regulations in Electrical Safety

1

Indian regulations in

Electrical Safety

P.LahiriBARC

2

Indian regulations.

• Indian Electricity Act-1910.

• Indian Electricity (Supply) Act- 1948.

• Indian Electricity Regulatory Commission Act-1998.

• The Electricity Act –2003.

• Indian Electricity Rules- 1956.

Repealed under section 185 of Electricity act -2003

3

• 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.

Objectives of regulations

4

Categories of agencies

• Supplier of electricity.

• Consumer of electricity.

• Electrical inspector.

• Electrical contractor and supervisors.

• Authorized persons.

5

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.

6

Quantitative effect of electric current (up to 3sec.) on human (source Daziel)

Effect mA

d.c a.c

60Hz 10kHz

M F M F M F

Perception threshold 5.2 3.5 1.1 0.7 12 8

Shock but not painful 9 6 1.8 1.2 17 11

Muscular control lost, breathing difficulty.

90 60 23 15 94 63

Ventricular fibrillation 500 500 100 100

7

Flash and flame burnThermal burns, Current flows typically external, Damage to skin

8

Electric shock and flash burn

9

EXPLOSION

Occurrence of blast

10

Classification of rated voltage as per IE rule

250V

650V

Low Voltage (LV)

Medium Voltage (MV)

High Voltage (HV)

Extra High Voltage (EHV)

33kV

Above 33kV

11

Authorization• Avoid chaos

• Fixing up of responsibility

• Ensures expertise

• Authorization.• Electrical isolation.

• Identification & display.

• Restriction of access.

• Inspection, testing etc.

• Preparedness for adversity.

• Other hazard precaution.

• Protection & interlocks.

• Clearances.

• Earthing.

• Reporting accidents.

12

Authorization ruleRequirement Applicable for Rule

Work to be executed by licensed electrical contractor.

All new, addition, alteration jobs having electrical scope except minor jobs.

45-(1), (3)

Safety officer to be authorized by owner with approval of electrical inspector.

Electrical installation with more than 250kW connected load

3, 4, 5, 6

Prior approval from electrical inspector to work

Any electrical work on live apparatus/ line

36 (2)

13

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.

3 (2A)

Assistants to above ITI & training from CEA approved institute

3 (2A)

14

Electrical isolation.

• Quick de-energization

• Ensure de-energization while on work

• Authorization.

• Electrical isolation.• Identification & display.






• Clearances.

• Earthing.


15

Electrical isolation(Rule)

Rating of service connection Isolation device

Rule

CB SFU*

LV, MV service connection 50-(b) (i) (ii)

upto 1000kVA at 11kV

Above 1000kVA at 11kV upto 2500kVA at 33kV Above 2500kVA at 33kV Any rating beyond 33kV

16

LV,MV

17

11k,33k

or

18

>33k

19

Electrical isolation device for transformers (Rule)

Rating of transformer Isolation device RulePri: Sec:

CB SFU* CB SFU*

Upto 630kVA and primary side less than HV

50-(b) (i) (ii)

upto 630kVA and primary side HV and above.

630kVA to 1000kVA irrespective of primary voltage

Above 1000kVA irrespective of primary voltage

20

Above 1000kVA

21

Primary HV

22

630kVA

23

Identification & display

• Electricity is invisible:-– 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.

• Authorization.

• Electrical isolation.







• Clearances.

• Earthing.


24

Identification & display (Rule)

Requirement Applicable for Rule

Display of danger notice.

Electrical installation rated MV and above.

35

Visual identification by distinct colour.

All conductors connected to earthing system

32(1)

Visual distinction of circuits, voltages, feeders etc.

All electrical installation 41

25

Restriction of access

• Thwart accidental or unauthorized access:-

• Authorization.








• Clearances.

• Earthing.


26

Restriction of access (Rule)

Requirement Applicable for Rule

Metallic covering which is electrically and mechanically continuous

All live conductors for indoor installations.

51(1)(a)

Metallic fencing of height not less than 1.8M.

Out door sub-station. 68(b)

27

Inspection testing & maintenance

• Ensure adequacy of safety related parameter:

• Maintaining safety related parameter within limit.

• Authorization.








• Clearances.

• Earthing.


28

Commissioning inspection (Rule)

Type of Installation

Type of test (Rule do not specify) interpreted.

Inspecting authority

Any installation upto MV (not generating plant)

Visual inspection.

Insulation resistance.

High voltage.

Earth resistance.

Any functional requirement.

Supplier.

Generating plant of capacity less than 10kW

Same as above Owner

29

Commissioning inspection (Rule) cntd.

Type of Installation

Type of test (Rule do not specify) interpreted.

Inspecting authority

Generating plant of capacity more than 10kW

Depending upon voltage level as desired by Electrical Inspector

Electrical Inspector.

HV or EHV installation

Visual inspection, insulation resistance, high voltage, earth resistance, functional tests and test as desired by Electrical Inspector.

Electrical Inspector.

30

Periodic inspection (Rule)Type of test Maximum

time interval.Record keeping duration

Test by inspector 5 years Not specified

Earth resistance for LV and MV installation

2 years 2 years.

Earth resistance for HV and EHV installation

1 year 2 year

Fire extinguishers 1 year Not specified

31

Preparedness.

• Mitigate the effect of fast acting electrical disaster

• Ensure correct course of action

• Authorization.








• Clearances.

• Earthing.


32

Preparedness (Rule)Essential Applicable for Rule

First-aid box, Restoration chart, Fire buckets

Every generating station, enclosed sub-station and enclosed switch station

43(2), 44(1), 43(1)

Two or more gas masks

1.Generating station with capacity of 5MW and above

2.Enclosed sub-station with transformation capacity of 5 MVA and above

43(3)

33

Preparedness (Rule)cntd.

Essential Applicable for Rule

Artificial respirator

Every manned high voltage or extra-high voltage generating station, sub-station or switch station

44(4)

Trained personnel for providing artificial respiration.

All attended generating station and sub-station.

44(3)

34

Possibility of success of artificial respiration

source Edition Electric Institute resuscitation manual

35

Other hazard precaution.

• Reduce potential initiating events of accident

• Authorization.








• Clearances.

• Earthing.


36

Other hazard precaution.(Rule)

Situation Safety measure RuleElectrical installation in explosive atmosphere

Explosion proof/ dust tight depending upon the hazardous zone as per IS5571

51(d)

Multistoried building with height more than 15M.

1. Power cable ducts shall not be used for other services

2. Power cable ducts shall have fire barrier at each floor crossing

50A-(4)

37

Other hazard precaution.(Rule)cntd..

Situation Safety measure RuleElectrical installation with more than 2000litres of oil

1.Baffle wall of 4hr fire rating between single phase banks and on consumer premise.

2.Oil soak pit for full quantity of oil

64(2)-(e)

Electrical installation with more than 9000litres of oil

1.Measures mentioned above.

2.Fire extinguisher.

3.Oil draining arrangement.

64-(2)(e)

38

Other hazard precaution.(Rule)cntd..

Situation Safety measure Rule

Substation and switch station in the basement

1.Entrance shall have 2hr fire rating fire resistance door

2.A curb at entrance to trap oil flow.

3.Direct access to transformer from outside

4.Transformer protection by automatic HVWSp/ CO2/ BCF/ BTM/ N2 injection and drain.

64-(2) (f)-(ii)

39

Other hazard precaution.(Rule) cntd..

Location based on oil inventoryTotal oil quantity in litre (includes transformer and other apparatus)

Location Rule

Indoor Out-doorIndl: building Res:/ com:

bldg. Any floor of

1st

Bs.Gr. Fl.

Other floors

No oil. 64 (2)2000 or less

2000 to 9000 9000 or more

40

Protection & interlocks.

• Avoid human errors

• Authorization.








• Clearances.

• Earthing.


41

Transformer protectionRating Mandatory relay

protectionRemark

Less than 630kVA and primary side less than HV

No relay based protection is mandatory

Not specified

Less than 630kVA and primary side more than HV

Over current/ short circuit relay etc for secondary CB.

Not specified but implied by R50(b)(ii)

630kVA to 1000kVA

Over current/ short circuit relay etc for secondary CB.

Not specified but implied by R50(b)(ii)

42

Transformer protection

cntd..

Rating Mandatory relay protection

Remark

1000kVA to 10MVA

1. Bucholz

2. Winding temp:

3. Oil temp:

R64(2)

More than 10MVA 1. Bucholz

2. Winding temp:

3. Oil temp:

4. Differential

R64(2)

43

HV & EHV installations interlocksSituation Preventive interlock Rule

Isolator and CB in series

Isolator operation not allowed when CB is closed.

64 (A) (1)

Earthing switch and isolator

Earthing switch can not be closed when isolator is closed

Two or more incomer feeders to a bus bar but not intended for parallel operation

Only one feeder can be switched on at a time

44

HV & EHV installations interlockscntd..

Situation Preventive interlock Rule

Two or more transformers in parallel

Secondary CB trips if primary of that transformer trips.

64 (A) (1)

Doors or gates give access to live parts

Doors can not be opened when any part is live.

Neutral switching device between neutral and earthing is used for generator

GCB can not be closed when neutral breaker is open.

45

HV & EHV installations protectionProtection against.

Type of relay Mandatory for Rule

Over current. Over current/ short circuit relay.

Any Equip., cable supply line etc.

64A (2)

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 voltage/ lightning

Lightning arrestor Overhead line terminations

92(1)

46

Other protectionsProtection for.

Type of relay Mandatory for Rule

Human safety.

ELCB/ RCCB/ etc.

Any installation having connected load more than 5kW at MV or above

61A

DC earthing. Over current relay between earthed middle conductor and earth.

DC three wire system

61 (1) (d) (i)

47

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 5- Unsafe or fibrillation

Time/ Current for a.c 50Hz

48

Clearances (physical spacing)

• Minimum air insulation clearance.

• Minimum space to work.

• Minimum space for escape.

• Authorization.








• Clearances.• Earthing.


49

Clearances for bare conductor other than overhead lines(Rule)

Voltage Section clearance (outdoor) in m.m.

Ground clearance (outdoor) in m.m

Rule

Upto 11kV 2600 2750

64

33kV 2800 3700

66kV 3000 4000

220kV 4300 5500

400kV 6500 8000

50

Clearance above ground of overhead lines across/ along a street (Rule)

Condition System voltage Clearance in mm

Rule

Across LV, MV 5800

77

HV 6100

AlongLV, MV 5500

HV 5800

Any where else

LV, MV, HV (upto11kV)

4600

HV(above 11kV) 5200

Every where EHV

5200 + 300 for every 33kV but not less than 6100

51

Clearance of overhead lines from building(Rule)

Condition System voltage Minimum clearance in mm

Vertical

(IE R 79)

LV, MV 2500

HV 3700

EHV 3700 + 300 for every 33kV

Horizontal

(IE R 80)

LV, MV 1200

HV upto 11kV 1200

HV above 11kV

2000

EHV 2000 + 300 for every 33kV

52

SECTION CLEARANCE

SC

Section clearance

SC

53

GC

GROUND CLEARANCE

GROUND LEVEL

Ground clearance

Height of tall man’s raised finger tip with raised hand-2.5m

54

Earthing system.

• Limit touch potential• Limit step potential• Safe predefined passage for

fault current• Facilitate detection of

incipient fault• Reduce neutral shifting

• Authorization.








• Clearances.

• Earthing.• Reporting accidents.

F

E

Et

E/X CURVE

Es

Earth Mat

X

1M 0.5M

Step & Touch potential

56

Earthing (Rule)Requirement Applicable for RuleEarthing terminal by Supplier.

LV consumer 33

Separate earthing terminal by supplier and consumer.

MV and above 33

Minimum two independent and redundant path with two earth electrode.

Earthing network for equipment, system. R61(2),

R61(3), R51(1)(b), R67(1)

All metallic part not intended to serve as conductor shall be earthed.

All electrical apparatus

Grounding of neutral. a.c electrical power supply system more than 125V

61(1)(a), 64(3)

57

Reporting of accidents

• Reporting for analysis.

• Fast reporting prevents suppression of facts.

• Authorization.








• Clearances.

• Earthing.


58

Reporting of accidents (Rule)Type of accident Report

formatMaximum period for reporting

Rule

Fatal involving loss or injury

Telegraphic

and

24hours44A

Written 48hours

Failure of transformer or reactor above 20MVA

Written 48hours 65(8)

59

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.

60

61

Clearance across the road

62

Clearance along the road

63

Clearance anywhere else

64

Clearance from building

Vertical clearance

Horizontal clearance

65

Fl-1

Fl-4

Fl-2

Electrical service shaft

Fire barrier

Cables

Fire barrier in cable duct

66

Ground clearance for bare conductor other than overhead lines(Rule)

Voltage Clearance in mm Outdoor

Upto 11kV

2750

33kV 3700

66kV 4000

220kV 5500

400kV 8000

Height of tall man’s raised finger tip with raised hand-2.5m

67

Phase to Phase(Rule)


Ph~Ph Ph~E Sec: Ground

11kV 460

33kV 915

66kV 1220

220kV 3350

400kV 4000

68

Phase to earth(Rule)


11kV 305

33kV 610

66kV 750

220kV 1675

400kV 3500

69

ClearancesIt 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 earthMinimum distance between live conducting parts and neighboring earthed parts.

Phase to earth

70


Phase to earth Phase to PhaseMinimum distance between live parts of different phases.

Phase to phase

71


Phase to earth

Phase to PhaseIsolating clearanceMinimum distance between two sides of an open isolator

Isolating clearance

72


Section clearanceMinimum distance between maintenance zone and nearest live part plus one stretched arm length of a person

Phase to earth

Phase to Phase

Isolating clearance

Section clearance

73


Ground clearanceMinimum distance between lowest point of support insulator and ground

Phase to earth

Phase to Phase

Isolating clearance

Section clearance

Ground clearance

74

CLEARANCES IN OUTDOOR

PH-TO PH

STRUCTURE

PHASETO EARTH

GANTRY

TOWER

Phase to earth & phase to phase clearance

P-E rule P-P rule

75

Isolating clearance

Isolating clearance

76

77

Safety provisions in IE Rules• Authorization.








• Clearances.

• Earthing.


78

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Indian regulations in Electrical Safety

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