Recommended
More Related Content
What's hot
What's hot (20)
Similar to Electrical safety
Similar to Electrical safety (20)
More from JaydevVadachhak
More from JaydevVadachhak (20)
Recently uploaded
Recently uploaded (20)
Electrical safety
- 2. CONTENTS 1. WHEN WE GETTING ELECTRIC SHOCK. 2. DIFFERENT CURRENTS. 3. FACTORS EFFECTING SEVERITY OF SHOCK. 4. PRECAUTIONS. 5. EARTHING. 6. FEW PROECTIVE DEVICES.
- 6. Electrical Shock An electrical shock is experience when a current flow through the body. The shock occurs when any part of your body completes a circuit. The maximum current that the human body can withstand for a short time i.e not more than 25milliseconds for 30mA. High voltages increase shock injuries because a higher voltage produces a greater current.
- 7. Electricity - The Dangers Shock Burns Falls Finally death of a person
- 8. Electrical Shock The response to electric shock could range from a faint tingling sensation to death. We can perceive a current as low as 1 milliamp. At 5 mA you will feel a slight shock. Änd it is a “let go current”.
- 9. Electrical Shock “Can’t Let Go” Current 10 mA to 30 mA Painful shock and sustained muscle contraction.
- 10. Electrical Shock
- 11. Electrical Shock
- 12. FACTORS THAT MAY AFFECT THE SEVERITY OF THE SHOCK
- 13. Electrical Shock Other factors that may affect the severity of the shock are: 1. The magnitude of the current. 2. Condition of the skin i.e. wet or dry 3.The phase of the heart cycle when the shock occurs. 4.The general health of the person prior to the shock. 5.Time of exposure. 6. Path way through the body. BODY RESISTANCE Dry Body = 1,00,000 Ώ Neither wet nor dry = 5000 Ώ Totally wet = 1000 Ώ
- 14. Electrical Shock Pathways 4. Left hand left foot path 3. Right hand right foot path 2. Right foot left foot path 1. Right hand left hand
- 15. When we come to know that person has received a shock , the what precautions have to be taken or First Aid for Electric shock
- 16. When we come to know that person has received a shock , the following precautions have to be taken or First Aid for Electric shock 1.Do not touch the victim with the bare hands when he is still in contact with electricity. 2.Shut off the supply immediately. 3.If the supply cannot be switched off immediately, use a non- conducting object has as dry wooden rod, broom, chair, rug or rubber doormat to push the victim way from the source of current. Never use a wet or metal object. If possible stand on something dry, non-conducting surfaces such as mat, folded news papers or dry wooden bases to push the victim.
- 17. 4. Once the victim is free, check his breathing pulse. If they have stopped or dangerously slow, initiate artificial breathing, threat third degree burns and get emergency health care. When breathing is re-established, treat the victim for shock by elevating the feet and cover the body with a blanket.
- 18. PREVENTION OF SHOCKS (OR) ELECTRICAL HAZARDS The following precautions may be take to prevent persons from getting shocks in the homes: 1. Care must be taken to see that ground points are properly provided to all the sockets to which electrical appliances are connected. 2. Proper earthing has to be provided periodically the earthing resistance has be checked to see that it does not exceed 3 to 5Ώ. 3. Install ground fault interrupts(GFCIs--The GFCI Receptacle is an electrical device that reduces the risk of severe or fatal electric shock to a user when an abnormal amount of current is in the circuit. ) in wall outlets located in bothroom, kitchens, basements, garages and outdoor boxes.
- 19. 4. Cover all electrical sockets with plastic safety caps i.e proper insulation. 5. Replacement of damaged parts immediately. 6. Discouraging the permanent use of extension cords. 7.Completely avoiding spilling of water or chemical near electrical apparatus.
- 21. WHAT DOES AN EARTHING DO?.
- 22. Earthing provides an alternative path to faulty current to flow into the earth.
- 23. GROUNDING The process of connecting the metallic frame (i.e. non-current carrying part) of electrical equipment or some electrical part of the system (e.g. neutral point in a star-connected system, one conductor of the secondary of a transformer etc.) to earth (i.e. soil) is called grounding or Earthing. Grounding or earthing may be classified as: • Equipment grounding • System grounding
- 24. Enclosure
- 25. EQUIPMENT GROUNDING The process of connecting non-current-carrying metal parts (i.e. metallic enclosure) of the electrical equipment to earth (i.e. soil) in such a way that in case of insulation failure, the enclosure effectively remains at earth potential is called equipment grounding. (i) Ungrounded enclosure (ii) Enclosure connected to neutral wire (iii) Ground wire connected to enclosure There can be three scenarios:
- 27. ENCLOSURE CONNECTED TO NEUTRAL WIRE
- 29. GROUND WIRE CONNECTED TO ENCLOSURE
- 32. Improperly Grounded Appliance with Short
- 34. PROTECTIVE DEVICES Protection for electrical installation must be provided in the event of faults such as short circuit, overload and earth faults. The protective circuit or device must be fast acting and isolate the faulty part of the circuit immediately. It also helps in isolating only the required part of the circuit without affecting the remaining circuit.
- 35. PROTECTIVE DEVICES The following devices are usually used to provide the necessary protection for electrical cirucits 1.Fuses 2.Miniature circuit breakers (MCB) 3.Earth leakage circuit breakers (ELCB) 4. Relays
- 36. FUSES
- 38. FUSES The fuse was invented in the year 1890 by Edison. Fuse is defined as a safety device(simple protective device) used in any electrical installation, which forms the weakest link between the supply and the load. For interrupting the current in the circuit under overload or fault conditions. It is a short length of wire made of lead / tin /alloy of lead and tin/ zinc having a low melting point.
- 39. Under normal operating conditions it is designed to carry the full load current. If the current increases beyond this designed value due any of the reasons mentioned above, the fuse melts (said to be blown) isolating the power supply from the load.
- 40. FUSES
- 42. MINIATURE CIRCUIT BREAKER(MCB) Nowadays we more commonly use miniature circuit breaker or MCB in low voltage electrical network instead of fuse. A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by excess current, typically resulting from an overload or short circuit.
- 43. Its basic function is to interrupt current flow after a fault is detected. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. Circuit breakers are made in varying sizes, from small devices that protect low-current circuits or individual household appliance, up to large switchgear designed to protect high voltage circuits feeding an entire city.
- 44. ADVANTAGES OF MCB 1. It automatically switches off the electrical circuit during abnormal condition. 2. Another advantage is, as the switch operating knob comes at its off position during tripping, the faulty zone of the electrical circuit can be easily be identified. But in case of fuse, fuse wire should be checked by opening fuse grip or cutout from fuse base, for confirming the blow of fuse wire.
- 45. 3.Quick restoration of supply can not be possible in case of fuse as because fuses have to be rewirable or replaced for restoring the supply. But in the case of MCB, quick restoration is possible by just switching on operation.
- 46. EARTH-LEAKAGE CIRCUIT BREAKER(ELCB) An Earth-leakage circuit breaker (ELCB) is a safety device used in electrical installations with high Earth impedance to prevent shock. It detects small stray voltages on the metal enclosures of electrical equipment, and interrupts the circuit if a dangerous voltage is detected. None of the protection devices like MCB, Fuse etc. can protect the human life against electric shocks or avoid fire due to leakage current.
- 47. ELCBs are available in sensitivity of 30, 100 and 300 mA. IEC(International Electro-technical Commission) specify 30mA sensitivity ELCB for human life protection.
- 48. RELAYS
- 49. APPLICATIONS OF RELAYS In the home, relays are used in refrigerators, washing machines and dishwashers, and heating and air-conditioning controls.
- 50. MULTIMETER
- 51. A multimeter or a multitester is also known as a VOM (Volt-Ohm-Milliammeter), is an electronic measuring instrument that combines several measurement functions in one unit. USES OF MULTIMETER 1.For measurement of DC current & DC voltages. 2.For measurement of AC current & AC voltages. 3.For measurement of resistance. 4.Time and Frequency measurement. 5.To check whether diode is working or not. 6.To check even continuity of circuit.
Editor's Notes
- Give a common example of each situation.
- Note that the word electrocution usually means death.
- Give a common example of each situation.
- Explain that experienced electricians who sometimes must deal with live wires always use the back of their hands to move the wires. If a current were present, the contracting muscles would cause the hand to pull away from the wire. Demonstrate this with your hand and some object representing a wire.
- Explain that experienced electricians who sometimes must deal with live wires always use the back of their hands to move the wires. If a current were present, the contracting muscles would cause the hand to pull away from the wire. Demonstrate this with your hand and some object representing a wire.
- The path of the current will determine which tissue will be damaged. Touch potential, 2. Step potential, 3 and 4 Touch/step potential Discuss the circumstances in which each of these pathways could occur. Ask which could have the most severe results. Explain that this is why it is strongly recommended that people working with exposed parts of electrical machines should work with only one of their hands. The best way to do this is to keep your left hand in your pocket. This is because if both hands make contact with the wrong surfaces, the current flows through the body from one hand to the other. This can lead the current to pass through the heart. If the current passes from one hand to the feet (No. 3), little current will probably pass through the heart.
- Electrical fires are different than other fires. Because water conducts electricity, throwing water on an electrical fire can cause the fire to get larger and can electrocute you.