Successfully reported this slideshow.
Upcoming SlideShare
Loading in …5
×

# Electrical safety

868 views

Published on

SHEQ FOUNDATION ELECTRICAL SAFETY

Published in: Education
• Full Name
Comment goes here.

Are you sure you want to Yes No
Your message goes here
• Be the first to comment

• Be the first to like this

### Electrical safety

1. 1. ELECTRICAL SAFETY 1
2. 2. INTRODUCTION INTRODUCTION • Electricity has become essential to modern life and it’s often not seen as a potential DANGER. • We use electrical energy everyday and are exposed to ELECTRICAL HAZARDS. • Main causes of accidents related to electricity are;• Main causes of accidents related to electricity are; - • Work on Live Circuits – 36% • Earth Leakage Circuit Breakers, ELCB (fuses) not Working – 10% • External Interference – 25% • Power cable damage/severance by vehicle or during earth works • Deteriorating Material – 29%Deteriorating Material 29%
3. 3. DEFINITIONS DEFINITIONS • Electricity - Electric Current is the flow (movement) of electrical charge through a medium: the flow of electrons through the electronic circuit. It is measured in AMPERES. • Voltage is the electrical force ‘pressure’ that causes current to flow in a circuit. It is measured in VOLTS • Resistance is anything that causes an opposition to the flow of electricity in a i it It i d i OHMScircuit. It is measured in OHMS. • The rate of flow of electrical current depends upon the voltage and resistance • Conductors are substances with very little resistance to the flow of electrical current e g metalscurrent, e.g. metals. • Insulators are substances with such a high resistance that they can be used to prevent the flow of electrical current, e.g. glass, rubber, plastic, and dry wood.
4. 4. ELECTRICAL HAZARDS ELECTRICAL HAZARDS/INJURIES El t i Sh kElectric Shock • Electricity travels in closed circuits, normally through a conductor. Shock results when the body becomes part of the electrical circuit or provides an earthing point; current enters the body at one point and leaves at anotherearthing point; current enters the body at one point and leaves at another. Electricity will always seek the path of least resistance. Typically, shock occurs when awhen a person contacts: • Both wires of an energized circuit. • One wire of an energized circuit to the ground/earthing pointOne wire of an energized circuit to the ground/earthing point. • A metallic part in contact with an energized wire while the person is also in contact with the ground/earthing point. Severity of the shock depends on:Se e ty o t e s oc depe ds o • Path of current through the body • Amount of current flowing through the body • Length of time the body is in the circuitLength of time the body is in the circuit
5. 5. Flow Of Electric The Flow Of Electric Current through the body is dangerous. A small amount of current running through the body for a few seconds cana few seconds can give the effects shown in the diagram. Detrimental effects areDetrimental effects are due to current flowing through the body & heightened withheightened with increasing current 6
6. 6. EFFECTS OF SHOCK EFFECTS OF SHOCK • The effects of current through the body is proportional to the currents intensityThe effects of current through the body is proportional to the currents intensity expressed in milliamperes. • Effects can range from a barely perceptible tingle to severe burns and immediate cardiac arrest The effects of electric shocks on the human body depends on : • Current and voltage • Resistance • Path through body • Duration of shock • Resistancees sta ce Electrical resistance of the human body varies with: • Amount of moisture on skin/atmosphere • Contact areaContact area • Wet condition will drastically reduce resistance • The larger the contact area, the lower the resistance
7. 7. OTHER HAZARDS OF ELECTRICITY OTHER HAZARDS OF ELECTRICITY Fires Electricity is one of the most common causes of home & workplace fires• Electricity is one of the most common causes of home & workplace fires • Defective or misused electrical equipment is a major factor Explosions El t i it id f i iti f l i i t i th• Electricity provides a source of ignition for an explosive mixture in the atmosphere • Ignition can be due to overheated conductors, defective equipment or arcing between contact pointsbetween contact points • Failure of insulating material Burns • Can be caused by the current passing through the body• Can be caused by the current passing through the body • Burns can also result from Arcing • Where two current carrying members make contact. • Current can jump from an electrical outlet/appliance and pass through the body• Current can jump from an electrical outlet/appliance and pass through the body Arc-Blast • High voltage currents arcing through air with high temperature Other Hazards associated with arc blast (thermal radiation pressure wave• Other Hazards associated with arc-blast (thermal radiation, pressure wave, projectiles)
8. 8. ELECTRICAL ACCIDENTS ELECTRICAL ACCIDENTS W k Li Ci it (P ti )Work on Live Circuits (Precautions) • Never work on electrical circuits or equipment without an approved PTW. • Never work on circuits or equipment with the power on A l LOTO (L k O t T O t) t th i it• Apply LOTO (Lock Out Tag Out) to the circuit • Check with Qualified Electrician that circuit is isolated. • Limit access to rooms, cabinets, electric boxes allowing only authorized personnelpersonnel • Do not attempt to do it yourself – leave it for professionals E th L k Ci it B k (ELCB) L ki t W ki (P ti )Earth Leakage Circuit Breakers (ELCB) - Lacking or not Working (Precautions) • Protection of the Circuits with over current circuit breaker, fuses. • Protection of People (grounding circuit) or proper earthing. Deteriorating Material (Precautions) • Inspection and Maintenance of safety equipment. • Control of the ELCB’s calibration and testing. • Grounding resistance measurement program
9. 9. MINIMIZING ELECTRICAL HAZARDS AT WORK MINIMIZING ELECTRICAL HAZARDS AT WORK Grounding (houses & equipment)g ( ) • Protects electrical system, equipment and Personnel • Creates a low resistance path to earth Guardingg • Entrance to rooms containing exposed live parts must be marked with warning signs forbidding unauthorized persons to enter. • Live parts of operating electrical equipment must be guarded against accidental contact. Locking and Tagging equipment • Source of electrical energy isolated from equipment undergoing maintenance (Electrical Isolation Procedure) Mechanical Protection Device e.g. fuses and circuit breakers • Designed to shut off current in the event of a ground fault, overload, or short circuit. Specific Personal Protective Equipment for electrical workers • e.g. Rubber hand gloves, mat, insulated tools, etc
10. 10. MINIMIZING ELECTRICAL HAZARDS MINIMIZING ELECTRICAL HAZARDS • Electric CordsElectric Cords • Hands must be dry when plugging and unplugging flexible cords Plugs and Receptacles • Electric plugs and sockets are designed for different currents and voltages• Electric plugs and sockets are designed for different currents and voltages • Only matching plugs and sockets will fit together • Do not overload sockets Always Inspect Electrical Equipment before use for:Always Inspect Electrical Equipment before use for: • Broken Plugs • Exposed/Broken Insulation Frayed Wiring• Frayed Wiring • any sign of damage/unsuitability Cable Routing D t th bl t t l d ( t t )• Do not expose the cables to external damage (rats, etc) • Avoid putting electric cables under the carpet/rug • Mark out cable routes visibly
11. 11. PORTABLE GENERATORS – Safe Use • Many workplaces and homes have electric generators for use in case of loss of electrical power supply. These generators also present hazards. P ti f P t bl G tPrecaution on use of Portable Generators • Follow manufacturers advice including grounding and maintenance. • DO NOT connect generator directly to building sockets. • Use the correct connection cable and change over. • Be sure that the main circuit breaker is OFF and locked out prior to starting generator DO NOT b i t i d L t h h t t t th• DO NOT bring generators indoor. Locate where exhaust gases cannot enter the house (CARBON MONOXIDE POISONING) • Carbon monoxide is a colourless and odourless gas produced from the generating set When inhaled it reduces your ability to utilize oxygengenerating set. When inhaled it reduces your ability to utilize oxygen. NOISE AND VIBRATION HAZARDS – keep generators as far away as possible from your home and work areas to avoid hearing loss and fatigue.your home and work areas to avoid hearing loss and fatigue. • Turn off generator and let it cool prior to refuelling. (FIRE HAZARD) • Store fuel away from your home and ignition sourcesStore fuel away from your home and ignition sources.
12. 12. CONCLUSION Avoid the following unsafe acts F il t d i l k t & t t d i i t i i ti• Failure to de-energize, lockout & tagout during maintenance, repair or inspections. • Use of defective and non-insulated tools. • Direct pull on power cords U i 3 i d i h 2 i l• Using 3-wire cord with a 2-wire plug. • Pushing exposed wires directly into socket without plugs. • Using water on electrical fires. Use CO2/DCP extinguishers. • Overloading outlets with too many appliances. • Blocking access to switches and circuit breakers. • Leaving electrical equipment energized (e.g. pressing iron) without attention (turn off d d f )and remove cord after use). • Not switching off / verifying power is off when making repairs. • Working in an elevated position near overhead lines. • Installing household antenna near overhead power supply lines.