1. Electrical Safety

2. In the next 45 min We will refresh our knowledge about,
Hazards related to electricity
Shock & Factors affecting shock
Shock protection measures
Residual Current Circuit Breaker
Site Specific Requirements
Systems & Procedures related to Electrical Safety

3. ELECTRIC SHOCK
It is sudden & accidental stimulation of the human body’s nervous system as a result of passage of electric current

4. Primary Hazards Electric shock Electric fire & explosion
Electric flash
Electric burns

5. Secondary Hazards Person falling from height
Dropping of tools & objects
Health hazards due to release of toxic gas & production of UV rays
Psychological effects

6. How Shock Occurs
You will receive a shock if you touch two wires at different voltages at the same time (Phase to Phase, Phase to Neutral, Phase to Ground)
Flashover involving part of human body

7. By simultaneously touching the phase and neutral conductor thus completing the circuit through his body R Y B N
LOAD HAVING
METALLIC BODY
ALTERNATOR

8. 2. By touching the phase conductor and standing on the ground
ELEC. EQPT.HAVING
METALLIC BODY
ALTERNATOR R Y B

9. 3. By touching a metallic part that has become live by itself being in contact with an energised wire N
ELEC. EQPT.HAVING
METALLIC BODY
ALTERNATOR R Y B

10. Resistance
Amount of Current
Severity of Shock
Path of Flow
Voltage

11. Path of flow of current in the Human Body

12. Body Resistance Body area Resistance (ohms)
Dry skin 1,00,000 to ,00,000
Wet skin to 5000
Internal body -
Hand foot to 600
Ear to ear

13. Person in touch P with live wire N I = V / R
POWER
SOURCE N
I = V / R
= 230 / A (Dry Condition)
= A
= 2.3 mA
I = 230 / (Wet Condition)
= A
= 46 mA

14. Effect of Electric Current on Human Body

15. Voltage
Higher the voltage - Higher the severity of shock.

16. PROTECTION FROM ELECTRICAL INJURIES
PREVENTION OF ELECTRICAL ACCIDENTS

17. Shock Protection Measures
Isolation
Double insulation
Earthing
Over Current Protection Devices
Residual Current Protection Devices

18. ISOLATION SWITCHES The switches should be connected in phase only
The switches should be easy and free to operate
Body of the metallic switches should be earthed
Every DB should be provided with a switch
It is advisable to keep switch as near as possible to the work-place

19. OVERCURRENT PROTECTION
FUSE
KITKAT TYPE
HRC TYPE
Miniature Circuit Breaker (MCB)
Fuses are proven safety devices for overload conditions
Check the fuses for their current ratings
Never replace fuse wire with ordinary copper or aluminium wire
High rupturable cartridge (HRC) fuses are now a days easily available and has advantages over traditional fuses

20. Double Insulation Insulation Another insulation added.
Double insulated power tools have non-metallic body
Need not be earthed (two point plug is sufficient)
Insulation
Functional
Protective

21. SYMBOL FOR DOUBLE INSULATED MACHINES
Double Insulation
Elec. Machine
Metallic Body
Elec. Machine
Nonconductive Body
SYMBOL FOR DOUBLE INSULATED MACHINES

22. Two Distinct Equipment Earthing
NEUTRAL EARTHING
EQUIPMENT EARTHING
Two Distinct Equipment Earthing

23. CORE BALANCE CURRENT TRANSFORMER
RCCB WORKING PRINCIPLE
No fault Condition I1 = I2
Fault Condition I1 > I2 (I1 = I2 + IP)
Tripping Condition IP > 30 mA T
EQUIPMENT L I1 I2 Ip N
CORE BALANCE CURRENT TRANSFORMER

24. RCCB & RCBO
IS Part 1, 2000
Residual current operated circuit breakers. Part 1: Circuit breakers without integral over current protection. ( RCCBs) (First Revision)
IS Part 2, 2001
Residual current operated circuit breakers for house hold and similar uses - Part 2: Circuit breakers with integral over current protection ( RCBOs) (First Revision)

25. RCCB (RESIDUAL CURRENT CIRCUIT BREAKER)

26. Residual Current Circuit Breaker
Standard Specification, 30 mA sensitivity , 63Amps, 4 poles.
Testing procedure
Testing the sensitivity
Test the RCCB weekly and record it.

27. Typical Sub Distribution Board
ELCB
63 A
30 mA

28. HAND LAMPS
Protect from contact and damage, 24V hand lamps are to be used.To be enclosed by glass surrounded by metal wire mesh

29. Portable Power Tools

30. Colour coding of Cables
Single phase supply
Phase - red
Neutral - black
Earth - green
Three phase supply
Phases
Red
Yellow
Blue

31. Cable Joints Staggered joints Joints are not to be overlapped
One primary insulation and an overall secondary insulation is to be done
Proper insulation tape are to be used
Jointing kit
CABLE 1
CABLE 2
3/4”

32. 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

33. Registers & Procedures
Weekly RCCB check register
Lockout / Tagout
Permit system

34. Clues that Electrical Hazards Exist
Tripped circuit breakers or blown fuses
Warm tools, wires, cords, connections, or junction boxes
Frequent tripping of RCCB
Worn or frayed insulation around wire or connection

35. Discussion

36. Thank You