What You Will Learn!
- Electrical hazards at workplaces.
- Electrical Hazards Controlling methods.
- Effect of Current and Voltage on human being.
- Electrical protection methods.
Description
Introduction
•Conductors – substances, such as metals, that have little resistance to electricity
•Insulators – substances, such as dry wood, rubber, glass and Bakelite, that have high resistance to electricity
•Grounding – a conductive connection to the earth which acts as a protective measure
BE SAFE:
•Burns
•Electrocution
•Shock
•Arc flash/arc blast
•Fire
Explosions
Hazards of Electrical Energy
•Electric current affects the body when it flow through.
•The basic unit of current is the amp.
•This is applied across the current which flow through a resistance of 1 ohm, When a voltage of 1 volt is applied across it.
•However, current as low as thousands of maps (milliamps) can have an adverse effect on the body.
•The given table an illustration of the type of effects various of currents can have on the body.
Electrical Protection Methods
Maintain safe distance from overhead power lines:
•Staying away
•Following table shows the safe power line clearance distance for various line voltages.
Earthing Standard
•Earthing means a low impedance return path of fualth current. Actually the earth now rarely serves as a part of the return path of the return Circuit but is being used mainly for fixing the Voltages of system neutrals.
•Earthing of current carrying conductor is known as a system earthing, while that of non-current carrying conductor or metal work is known as Equipment Earthing.
•The farmer is essential to the security of the system and the latter to the safety of persons, property, and animals
•IS:3043, code of practice for Earthing and SP 30 National Elective Code must be referred for details of Earthing.
Following is the synopsis of Earthing standards mentioned is Section 12, Part I of our National Electric Code :
The purpose of system earthing is to preserve the security of the system.
1. There should be two separate and distinct connections with earth through an earth electrode.
2. The earth system resistance should be such that the fault should operate the protective gear
(fuses or circuit breaker) to isolate the faulty portion.
3.The purpose of equipment earthing is to protect the equipment from danger to life or risk of
Fire due to leakage of current through the metal work and through the person in contact. The
Leaking current operates the protective gear due to earthing.
4. In case of high and extra high voltages, the neutral points shall be earthed by two or more
Separate electrodes.
5. Earth electrodes shall be provided at generating stations, substations and consumer premises
as per requirements.
Classification of Hazardous Areas
•Zone 0 Areas : Here hazardous atmosphere exists continuously viz., the vapour space of closed. process vessels, storage tanks or closed containers. Any spark will certainly lead to fire or explosion. Therefore, any electrical apparatus in this zone must afford an absolute protection.
•Zone 1 Areas : Here hazardous atmosphere is likely to exist at any time. Therefore the fullest. practicable measures should be applied to prevent a hazardous electrical condition at any time and in any circumstances
•Zone 2 Areas : Here hazardous atmosphere is likely to occur only under abnormal operating conditions. This classification is applicable only where a fire or explosion hazard is unlikely and may be caused only by the simultaneous and improbable occurrence of an arc or spark resulting from an electrical failure and a hazardous atmosphere arising through failure of the conditions of control.
Who Should Attend!
- For Industrial persons.
