Chapter no: 01

Safety and Prevention of Accident Marks:10

Safety symbols used in industry and also write what the symbols stand for.

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 Precautions to be taken to avoid fire due to electrical reasons:-
1. Overloading on cables/wires/machine should be avoided
2. Frequently checking of electrical cables, wires appliances, and closely inspect cords
and plugs.
3. Correct rating of fuse/MCB/switch gear etc. should be used in the circuit.
4. Do not use of too many device plugged into a circuit.
5. Joint in wiring/cabling must be mechanically & electrically sound
6. Joints in wiring must be sound.
7. There should not be any loose connection in the electrical installation.
8. Replace deteriorated cables, wires, etc. by new one.
9. Do not store highly flammable liquids near(close to) electrical oven/furnace to avoid fire.
10. Do not keep electric heaters near curtains or furniture.
11. Use ground fault protection. Like ELCB/earth fault relay.
12. Test electrical safety devices
13. Do not make safety devices inoperative.
14. Maintenance should be done strictly as per schedule.
15. Use of superior quality of material ISI mark.
16. Replace faulty electrical installation and outdated appliances.
17. Replace Old electrical sockets and unsafe appliances

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Factors on which earth resistance depends:-
1. Moisture content in soil
2. Dissolved salts in soil
3. Soil Condition
4. Size of earth pit
5. Climate Condition
6. Size of earth electrodes
7. Metal of earth plate and earth wire.
8. Number of earth pits / erath electrode
9. Temperature of soil
10. Depth of electrode embedded in the earth.
11. Lengthen the earth electrode in the earth.
14. Resistance of the surrounding earth.
15. Physical Composition of soil
16. Effect of grain size and its distribution
18. Size and spacing of earth plate and size of conductor.

Factors on which severity of electric shock depends.

The severity of shock depends on following factors.
1. Magnitude voltage of the system.
2. The period or duration for which the area of contact with lives part.
3. It is also depends on supply system i.e. A.C or D.C.
4. Frequency of supply
5. Body resistance (If wet resistance of body reduces)
6. General health of human contact with lives part.
7. Path of current through body.
8. The phase of the heart cycle when the shock occurs
9. The presence of moisture in the environment.

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 OR

Safety precautions to be followed while working with an electric installation.

Following are some safety precautions to be taken to followed:
1. Only qualified men do the work, untrained person should not allow handling electrical
equipment.
2. Do not allotted work to untrained person (worker) to handle electrical equipment.
3. Do not allow visitors & unauthorized persons to touch or handle electrical equipment.
4. Wear appropriate clothing (loose clothing is avoided)
5. Use shoes with rubber soles to avoid shock.
6. Use approved discharge earth rod for before working.
7. Do not wear suspended Necklace, arm bands, finger ring, key chain, watch with metal parts
while working.
8. Do not work on live circuits without express order of the person in charge.
9. For major work take permit to shut down the supply from authority.
10. Always obey the safety instructions given by the person in charge.
11. Do not work without authority & operating switches without knowledge.
12. Do not work under unfavorable condition such as rainfall, Fog, high wind.
or shadows.

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14. Do not Do the work if you are not sure or knowledge of the condition of equipment/
machine.
16. Use proper insulated tools & safety devices.
18. Never touch a wire till you are sure that no currents are flowing.
19. Switch off the supply before starting the work.
20. Do not make safety devices inoperative.
21. Insulate yourself on the insulating material like wood, plastic etc. before starting the work on
live main.
22. Never speak to any person working upon live mains.
23. Do not sacrificing safety for speed.
24. Use proper instrument to test the circuit.
25. Always use proper insulated tools, rubber gloves, safety devices while working.
27. Make habit to look out for danger notice, caution board, flags, and tags.
28. Do not touch or operate switches when your hands are wet.
29. Your hand & feet must be dry (not wet) while working on live main.
30. Place yourself at safe distance from working equipment.
32. Correct rating of fuse/MCB etc. should be used in the circuit.
36. The earth connection should be perfectly sound & proper.
37. Over loading of equipments / circuit should be avoided.
38. Do not go carelessly near running belts on machines.
39. Do not expose your eyes to an electric arc.
40. Rubber mats must be placed in front of electrical switch board/ panel.
41. Ground all machine tools, body, and structure of equipments.
42. Earthing should be checked frequently.
43. When working on live equipment obey proper instruction.
44. Do not work on defective equipment.
45. Do not use defective material..
47. By the use of proper rating protective devices with the electrical circuits.
48. Electrical installation & equipments used in hazards area should be satisfied the
specification/type of protect.
50. Overloading on cables/wires/machine should be avoided.

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51. Do not use of too many device plugged into a circuit.
52. Correct rating of fuse/MCB/switch gear etc. should be used in the circuit.
54. Replace deteriorated cables, wires, etc. by new one.
55. Use ground fault protection. like ELCB/earth fault relay.
56. Test electrical safety devices.
58. Replace faulty electrical installation and outdated appliances.
59. Replace Old electrical sockets and unsafe appliances.
60. Maintain clearance as per voltage level.

Importance and purpose of earthing.

Importance and purpose of earthing is as below:-
1. To provide an alternative path for the leakage current to flow towards earth.
2. To save human life from danger of electrical shock due to leakage current.
3. To protect high rise buildings structure against lightening stroke lightening arrester is used for
this there is necessity of earthing.
4. To provide stable platform for operation of sensitive electronic equipments there is necessity
of earthing.
5. For proper working of earth fault protection system, there is necessity of earthing.
6. To keep the potential of equipment body (frame) below the earth potential in the event of fault
from safety point of view.

Methods used for reducing earth resistance.

1. Earth pit of more depth & width- breadth should be made.
2. Use of higher size/cross section of earthing material like earthing plate, earthing rod. earthing
pipe, earthing wire/strip reduces earth resistance.
3. Use of copper material for earthing reduces earth resistance than use of aluminum material
4. Earth pit are generally filled with alternate layer of charcoal & salt up to 4 feet from the
bottom of the pit.
5. Poured sufficient salt water in earth electrode pit.
6. Use chemical or coke/charcoal to increase conductivity,
7. Use earth conductor without joint in between.

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8. Tighten the earth connections.
9. Remove Oxidation on joints.
10. Earth resistance can be reduced by increasing number of earth electrodes inter connected in
parallel.
11. The electrodes and earth continuity conductor used in the circuit should be of same material
i.e. copper or galvanized.
12. Electrodes should be placed in the earth in the upright vertical position.

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Do’s and Don’ts regarding safety while working on electrical installations
Do’s

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Don’ts:

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Methods of Neutral Grounding. State difference between Earthing and grounding.
Neutral Grounding connections are of three types:
1. Solid earthing
2. Resistance earthing
3. Reactance earthing

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Distinguish between installation earthing and system earthing.

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Fire extinguisher used on live electrical circuit.

Following are the fire extinguisher used on live electrical circuit.

1) Dry powder fire extinguisher
2) Carbon dioxide (Co2) fire extinguisher.

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