Electrical Part Definitions:
1. Current: “Current is a measure of the amount of electrical charge transferred per unit time”. It represents the flow of electrons through a conductive material. The current is a scalar quantity. The SI unit of electrical current is the ampere, defined as 1 coulomb/second-Electrical hazard.
2. Voltage: “Voltage can be defined as a measurement of the energy contained within an electric field, or an electric circuit, at a given point” Voltage is a scalar quantity. The SI unit of voltage is the volt, such that l volt = 1 joule/coulomb.
3. Ohm’s law: “The direct current flowing in a conductor is directly proportional to the potential difference between its ends” It is usually formulated as V = IR, Where; V is the potential difference or voltage I is current, R is the resistance of the conductor-basic electrical safety.
4. Earthing: “Earthing is the process of connecting an earth conductor to the earth electrode”-electrical hazard OSHA. Earthing is basically the same thing as grounding. It helps to prevent electric shocks by providing a low impedance, low resistance, return path for any fault current to get back to the distribution panel. This high return fault current will cause the circuit’s breaker to trip and disconnect the fault.
5. Fuse: “A fuse is a safety device which is used to protect electrical circuits from overloading” Fuse is a piece of wire of a material with a very low melting point. When a high current flows through the circuit due to overloading or short circuit. the wires get heated and melts. As a result, the circuit is broken and current stops flowing-Electrical hazards.
6. A.C. current: “In alternating current (AC) the movement of electric charge periodically reverses direction” AC is the form in which electric power is delivered to businesses and residences-electrical hazard in the workplace.
7. D.C. current: “Direct current (DC) is the unidirectional flow of electric charge” Direct current is used to charge batteries, and in nearly all electronic systems, as the power supply. Very large quantities of direct-current power are used in the production of aluminum and other electrochemical processes- Electrical hazard.
8. ELCB: “An Earth Leakage Circuit Breaker (ELCB) is a safety device used in electrical installations with high earth impedance to prevent shock”
9. MCB: “Miniature Circuit Breaker (MCB) is a device protecting against overcurrent conditions, the modern equivalent of a fuse, with the advantage that it can be reset”-electrical safety precautions.
10. Transformer: “A transformer is an electrical device used to convert AC power at a certain voltage level to AC power at a different voltage but at the same frequency”
11. Conductor: “Conductor is a material allowing the flow of electric current”
12. Overload: “Overload is an electrical load that exceeds the available electrical power”
13. Short circuit: “A short circuit is an accidental path of low resistance which passes an abnormally high amount of current”-testing earth continuity. A short circuit exists whenever the resistance of a circuit or the resistance of a part of a circuit drops in value to almost zero ohms. A short often occurs as a result of improper wiring or broken insulation of Electrical safety.- Electrical hazard.
14. Static electricity “Static electricity refers to the buildup of electric charge on the surface of objects” The static charges remain on an object until they either bleed off to ground or are quickly neutralized by a discharge,
Safety measures for electrical work:
- General Safety Measures for electrical work should include:
- 1. Proper earthing and double earthing. General earthing for big power, up to 0.5 ohms, big substation 1 ohm, small substation 2 ohm and tower and other places up to 8 ohms. Due to minimum eating resistance, leakage current pass4es through it and not through a person. The earthing should be inspected, tested, and maintained properly. There should be a regular practice to check to earth. The minimum voltage between the ground and the earth wire should be 30 v-water and electricity safety.
- 2. Use of approved insulated tools, rubber mats, shockproof gloves and bots, tester, fuse puller or tong, D.O. rod, safety belt, hand lamp, wooden or insulated ladder, and not wearing a metal ring, chain, etc.
- 3. Switches on the live line. Fused switches and air-current breaks should be used-protection from electric shock.
- 4. Avoid temporary wiring. Avoid hurry and chance-taking. Avoid left-hand touching-electrical safety hazards.
- 5. Employ qualified and trained electricians.
- 6. Low voltage (24 V AC or 110V DC) in a hazardous area.
- 7. Good insulated and tested wiring.
- 8. Isolation of machine/ equipment before use.
- 9. Work permit system as given in IS: 5216-1969. Follow this IS for electrical work-electrical safety in the construction site.
- 10. Safety tags and safety warning notices.
- 11. Use of machine/ equipment within their limits. i.e. no overloading.
- 12. Placement of oil type transformer outdoor.
- 13. Auxiliary room, battery room, and control room to be separated.
- 14. Two exits to each electrical room-electrical awareness.
- 15. Switchgear of the supply company should be separated from that of the consumer by a fireproof wall.
- 16. Precautions against thermal and mechanical stress, moisture, dust, and overvoltage relay to protect from overvoltage.
- 17. Guard on transmission lines to prevent fault due to birds.
- 18. Vermin proof enclosure for indoor switchgear.
- 19. Use of electrical shock guard (ELCB) and 3-pin plug and socket to have a proper earth connection-Electrical hazard
- 20. Use of reactors or current limiting impendence or underground neutrals to reduce fault levels-electrical safety
- 21. Use protective relays, circuit breakers, and rated fuses to control the current and to isolate the faulty equipment speedily and automatically. Check before closing and OCB for high voltage lines.
- 22. Use of grounding mat of low ohmic value and all non-current-carrying parts to be connected to the grounding grid by duplicate earth and segregated noncurrent carrying metallic parts to be electrically bonded.
- 23. Record of ground resistance values and the physical condition of the grounding mat-hse electrical safety.
- 24. Temperature-sensitive alarm and protective relays to make alert and disconnect equipment before overheating-electrical safety.
- 25. Interlocks to put into and out of service equipment correctly.
- 26. Testing for high voltage, timing, polarity, and insulation resistance.
- 27. Cleaning and application of silicon grease to insulators to reduce pollution deposits-qualified electrical workers.
- 28. Safe cable trenches and preferably armored cables.
- 29. Transformers with oil safety, DO. Fuse, L.T. fuse, MCB, MCCB, and automatic fire protection system.
- 30. Generators and motors with fireproof doors automatic fire protection systems.
- 31. Ready CO2 type and other fire extinguishers.
- 32. Double communication systems with critical areas.
- 33. Clear approach available for firefighting squad.
- 34. Flame and shock detectors and central fire annunciation system for fire safety.
- 35. Diesel pump set for required fire water pressure.
- 36. Good housekeeping including good maintenance of all electrical installations.
- 37. Adequate working space and means of access around each apparatus.
- 38. First-aid boxes and respiratory equipment ready. Training for artificial respiration to save a life from shock.
- 39. Prevent higher humidity and temperature near the electric installation. Work with full protection in rain.
- 40. Use of flameproof/ explosion-proof equipment in flammable/ explosive areas. 41. Earthing and bonding of solvent carrying pipelines and equipment
Electrical work in hazardous area Classification of Hazardous Areas:
In chemical, petrochemical, refinery, and fertilizer factories and also in coal mines, combustible/ explosive dust, vapor, and gases may evolve during normal or abnormal operating conditions. These gases coming into contact with air make an explosive air-gas mixture which is hazardous to the installation of electrical apparatus as well as to the workers. IS: 5572 divides the hazardous area (containing flammable gas or vapor capable to be ignited) into following three zones for the purpose of appropriate electrical installation-OSHA electrical safety
1. Zone 0 Areas:
Here hazardous atmosphere exits continuously viz., the vapor 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 absolute protection. It is recommended that the use of electrical apparatus should be avoided in this zone, but when it is not practicable, IS: 5571 (guide for the selection of electrical equipment for hazardous areas) should be followed-earth continuity
2. Zone 1 Areas:
Here the hazardous atmosphere is likely to exit at any time. Therefore the fullest practicable measures should be applied to prevent a hazardous electrical condition at any time and in any circumstance. Recommended types of electrical apparatus and wiring for use in zone 1 areas are given in IS 5571-electrical safety in the workplace
3. Zone 2 Areas:
Here the 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 the failure of the conditions of control. It presupposes that any hazardous atmosphere resulting from an abnormal occurrence is rapidly dispersed so that possible contact with the electrical apparatus is of minimum duration. Any situation which allows a hazardous atmosphere to collect, such as pit or trench, although, it may be in the open air, shall in itself be classified as zone 1 area; even though the surrounding area is classified as zone 2. Where doubts exist in any specific case, a zone 1 classification should be adopted.
Electrical shock treatment:
1. If the accident occurs indoors switch off the current from the mains supply-electrical safety inspection
2. If this cannot be done immediately, remove the victim without directly contacting his skin.
3. If the accident occurs outdoors, push the line wire or conductor away from the victim with a dry, unpainted wooden pole or pull it away with a loop of dry rope or any other non-conductive material.
4. Send for medical help and start artificial respiration immediately
5. Continue persistent artificial respiration till the patient revives or till there are no chances left. There are cases on record where revival has occurred after even 3 hours of persistent effort.