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- 1. UNIVERSITY OF ENGINEERING AND TECHNOLOGY PESHAWAR ELECTRONICS ENGINEERING DEPARTMENT ELE-410 INDUSTRIAL ELECTRONICS LECTURE # 02 BY DR. ADAM KHAN 1
- 2. • Text Book: Electric Motors and Control Systems • By Frank D Petruzella 2nd Edition Chapter 1: Safety in the Workplace 2
- 3. Electric related Injuries • Electric Burn, which are a result of electric current flowing through the tissues or bones. Can affect skin surface or deeper layers of the skin • Arc burns, which are a result of an extremely high temperature caused by an electric arc (as high as 35,000°F) in close proximity to the body. Occurs due to poor electric contact or failed insulation • Thermal contact burns, which are a result of the skin coming in contact with the hot surfaces of overheated components. 3
- 4. What will you do if a person suffers a severe shock?? 4
- 5. Arc Flash Hazards • An arc flash is the ball of fire that explodes from an electrical short circuit between one exposed live conductor and another conductor or to ground. • It creates enormous amount of energy ,which results in damage of equipment and can cause injury or even death of life. 5 Arc Flash
- 6. Arc Flash Hazards (Contd….) • Electrical short circuits are either • A bolted fault is current flowing through bolted bus bars or other electric conductors. • The normal circuit current bypasses the load through a very low conductive path • All equipment needs to have adequate interrupting ratings to safely contain and clear the high fault currents • An arcing fault is current flowing through the air (a higher-resistance medium). “the arc fault current is always lower than the bolted fault current” • An arc blast is a flash that causes an explosion of air and metal that produces dangerous pressure waves, sound waves, and molten steel. 6
- 7. Arc Flash Hazards (Contd….) • Eighty percent of electrical workplace accidents are associated with arc flash. • It involve burns or injuries caused by intense heat or showers of molten metal or debris. • an arc flash produces an intense flash of blinding light, capable of causing immediate vision damage and can increase a worker’s risk of future vision impairment. “Arcs can produce temperature four times hotter than the surface of the sun” • Safety standards such as National Fire Protection Association (NFPA) 70E have been developed to minimize arc flash hazards. 7
- 8. Personal Protective Equipment • Construction and manufacturing worksites, by nature, are potentially hazardous places. • Safety has become an increasingly large factor in the working environment. • A safe operation depends largely upon all personnel being informed and aware of potential hazards • Safety signs and tags indicate areas or tasks that can pose a hazard to personnel and/or equipment. 8
- 9. Personal Protective Equipment (Contd..) • To perform a job safely, the proper protective clothing must be used. • Appropriate attire should be worn for each particular job site and work activity 9
- 10. Personal Protective Equipment (Contd..) • A wide variety of electrical safety equipment is available to prevent injury from exposure to live electric circuits. • Electrical workers should be familiar with safety standards such as NFPA- 70E 10
- 11. Personal Protective Equipment (Contd..) • All electrical protection equipment must be listed and may include the following: • Rubber Protective Equipment—Rubber gloves are used to prevent the skin from coming into contact with energized circuits. • A separate outer leather cover is used to protect the rubber glove from punctures and other damage. • Rubber blankets are used to prevent contact with energized conductors or circuit parts when working near exposed energized circuits. • Insulating value and voltage value of rubber blanket should be checked • Insulating gloves must be given an air test, along with inspection. 11
- 12. Personal Protective Equipment (Contd..) • Protection Apparel—Special protective equipment available for high- voltage applications include high voltage sleeves, high-voltage boots, nonconductive protective helmets, nonconductive eyewear and face protection, switchboard blankets, and flash suits. • Hot Sticks—Hot sticks are insulated tools designed for the manual operation of high-voltage disconnecting switches, high-voltage fuse removal and insertion, as well as the connection and removal of temporary grounds on high-voltage circuits. • hot stick is made up of two parts, the head, or hood, and the insulating rod. 12
- 13. Personal Protective Equipment (Contd..) • Shorting Probes—Shorting probes are used on de-energized circuits to discharge any charged capacitors or built-up static charges that may be present when power to the circuit is disconnected. • When installing a shorting probe, first connect the test clip to a good ground contact. • Next, hold the shorting probe by the handle and hook the probe end over the part or terminal to be grounded. • Never touch any metal part of the shorting probe while grounding circuits or components. • Face Shields—Listed face shields should be worn during all switching operations where there is a possibility of injury to the eyes or face from electrical arcs or flashes, or from flying or falling objects that may result from an electrical explosion. 13
- 14. Personal Protective Equipment (Contd..) • To maintain a high level of electrical safety while you work, there are a number of precautions you should follow: • Never take a shock on purpose. • Keep material or equipment at least 10 feet away from high-voltage overhead power lines. • Do not close any switch unless you are familiar with the circuit that it controls and know the reason for its being open. • When working on any circuit, take steps to ensure that the controlling switch is not operated in your absence. Switches should be padlocked open, and warning notices should be displayed (lockout/tagout). 14
- 15. Personal Protective Equipment (Contd..) • Avoid working on “live” circuits as much as possible. • When installing new machinery, ensure that the framework is efficiently and permanently grounded. • Always treat circuits as “live” until you have proven them to be “dead.” Presumption at this point can kill you. It is a good practice to take a meter reading before starting work on a dead circuit. • Avoid touching any grounded objects while working on electrical equipment. 15
- 16. Personal Protective Equipment (Contd..) • Remember that even with a 120 V control system, you may well have a higher voltage in the panel. Always work so that you are clear of any of the higher voltages. (Even though you are testing a 120 V system, you are most certainly in close proximity to 240 V or 480 V power.) • Don’t reach into energized equipment while it is being operated. This is particularly important in high-voltage circuits. • When working on live equipment containing voltages over approximately 30 V, work with only one hand. • Safely discharge capacitors before handling them. Capacitors connected in live motor control circuits can store a lethal charge for a considerable time after the voltage to the circuits has been switched off. • Although Article 460 of the National Electrical Code (NEC) requires an automatic discharge within 1 minute, never assume that the discharge is working! 16
- 17. Personal Protective Equipment (Contd..) • Confined spaces can be found in almost any workplace. • In general, a “confined space” is an enclosed or partially enclosed space that: • Is not primarily designed or intended for human occupancy. • Has a restricted entrance or exit by way of location, size, or means. • Can represent a risk for the health and safety of anyone who enters. 17 OSHA permit is required to enter for work in Confined spaces