ELECTRICAL SAFETY

ELECTRICITY – THE DANGERS About 5 workers are electrocuted every week

Causes 12% of young worker workplace deaths

Takes very little electricity to cause harm

Significant risk of causing fires

ELECTRICITY – HOW IT WORKS

Electricity is the flow of energy from one place to another

Requires a source of power: usually a generating station

A flow of electrons (current) travels through a conductor

Travels in a closed circuit

ELECTRICAL TERMS

Current -- electrical movement (measured in amps)

Circuit -- complete path of the current. Includes electricity source, a conductor, and the output device or load (such

as a lamp, tool, or heater)

Resistance -- restriction to electrical flow

Conductors – substances, like metals, with little resistance to electricity that allow electricity to flow

Grounding – a conductive connection to the earth which acts as a protective measure

Insulators -- substances with high resistance to electricity like glass, porcelain, plastic, and dry wood that prevent electricity from getting to unwanted areas

ELECTRICAL INJURIES

There are four main types of electrical injuries:

Direct: Electrocution or death due to electrical shock Electrical shock Burns

Indirect - Falls

ELECTRICAL SHOCK

An electrical shock is received when electrical current passes through the body.

You will get an electrical shock if a part of your body completes an electrical circuit by…

Touching a live wire and an electrical ground, or Touching a live wire and another wire at a different voltage.

SHOCK SEVERITY

Severity of the shock depends on:Path of current through the bodyEar to ear – 100 ohmsHand to foot – 500 ohmsDry skin- 350 K ohmWet skin-1000 ohm

SHOCK SEVERITY

Amount of current flowing through the body (amps) Depends on-

– The voltage of the source

– Body resistance along the current path– The current capacity of the source

an automobile ignition system puts out approximately 30,000 volts

but the current capacity of the source is well below lethal current levels

at the opposite extreme touching a 30 vlts battery with a high current capacity can result in death.

SHOCK SEVERITY

Duration of the shocking current through the body,

LOW VOLTAGE DOES NOT MEAN LOW HAZARD

DANGERS OF ELECTRICAL SHOCK

Currents above 10 mA* can paralyze or “freeze” muscles.

Currents more than 75 mA can cause a rapid, ineffective heartbeat -- death will occur in a few minutes unless a defibrillator is used

75 mA is not much current – a small power drill uses 30 times as much

* mA = milliampere = 1/1,000 of an ampere

READINGS EFFECTS

SAFE CURRENT VALUES 1 mA or less

Causes no sensation –not felt

1 mA to 8 mA Sensation of shock, not painful; individual can let go at will since muscular control is not lost

8 mA to 15 mA Painful shock; individual can let go at will since muscular control is not lost

15 mA to 20 mA Painful shock; control of adjacent muscles lost; victim cam mot let go

UNSAFE CURRENT VALUES50 mA to 100 mA

Ventricular fibrillation – a heart condition that can result in death is possible

100 mA to 200 mA Ventricular fibrillation occurs

200 mA and over Severe burns, severe muscular contractions – so severe that chest muscles clamp the heart and stop it for the duration of the shock. (this prevents ventricular fibrillation)

As the current rises, the shock becomes more severe. Below 20 mA, breathing becomes labored; it ceases completely even at values below 75 mA. As the current approaches 100 mA ventricular fibrillation occurs. This is an uncoordinated twitching of the walls of the heart's ventricles

it is necessary to perform artificial respiration to try to get the person breathing again; or if the heart is not beating, cardio pulmonary resuscitation (CPR) is necessary.

Artificial ventilation should be given only when the breathing has stopped. Do not give artificial ventilation to any person who is breathing naturally

The comparison between the dangers of alternating current and direct current has been a subject of debate. DC tends to cause continuous muscular contractions that make the victim hold on to a live conductor, thereby increasing the risk of deep tissue burns. On the other hand, mains-frequency AC tends to interfere more with the heart's electrical pacemaker, leading to an increased risk of fibrillation. AC at higher frequencies holds a different mixture of hazards, such as RF burns and the possibility of tissue damage with no immediate sensation of pain. Generally, higher frequency AC current tends to run along the skin rather than penetrating and touching vital organs such as the heart. While there will be severe burn damage at higher voltages, it is normally not fatal.

BURNS Most common shock-related injury

Occurs when you touch electrical wiring or equipment that is improperly used or maintained

Typically occurs on hands

Very serious injury that needs immediate attention

FALLS Electric shock can also cause indirect injuries

Workers in elevated locations who experience a shock may fall, resulting in serious injury or death

ELECTRICAL HAZARDS ELECTRIC SHOCK

ELECTRICAL BURNS

FIRE AND EXPLOSION

FAILURE OF EQUIPMENT CONTROL

INADVERTANT START OF MACHINE

FALL OF PERSON DUE TO SHOCK

CANCER DUE TO ELECTROMAGNETIC RADIATIONS

LIGHTINING STROKE

CAUSES OF ELECTRICAL ACCIDENTS

MANUAL

UNAUTHORISED WORKING

WORK BY INEXPERIENCED PERSON

OVER CONFIDENCE

POOR SUPERVISION

IMPROPER SHUT DOWN

VIOLATION OF SAFE WORKING PROCEDURES

CAUSES OF ELECTRICAL ACCIDENTS

TECHNICAL

FAULTY EQUIPMENT

LACK OF EARTHING

POOR ILLUMINATION

INSULATION FAILURE

SUBSTANDARD MATERIAL

LIVE CONDUCTOR TOUCHING ENCLOSURE

OVERLOADING

IN CORRECT FUSES

WRONG SETTING OF RELAYS

POOR MAINTENANCE

STATIC ELECTRICITY

CAUSES OF INSULATION FAILURE HIGH TEMPERATURE

ENTRY OF MOISTURE

LOOSE CONTACT

VIBRATION

ENTRY OF INSECTS AND LIZARDS

TRACKING THROUGH DIRTY AND MOISTURE INSULATION SURFACES

AGING

STATIC ELECTRICITY

Static electricity is often created when two objects that are not good electrical conductors are rubbed together, and electrons from one of the objects rub off onto the other. This happens, for example, when combing one's hair or taking off a sweater. Sudden releases of built-up static

electricity can take the form of an electric arc .

Positive ions

Negative ions

Flow of liquid hydrocarbons

Movement of belt away from the pulley

Risk of fire can be avoided by providing conducting path for flow of static charges or by eliminating flammable Atmosphere

MEASURES TO PREVENT ELECTRICAL ACCIDENTS

EARTHING

LOW VOLTAGE IN CONFINED PLACES

ISOLATING TRANSFORMERS-AS THE SECONDARY WINDING IS NOT EARTHED , NO CURRENT WILL FLOW EVEN LIVE CONUCTOR OF EQPT COMES IN TO CONTACT

LIGHTNING PROTECTION

PROTECTIVE RELAYS

DOUBLE INSULATED TOOLS-SECOND LAYER OF INSULATION –PROTECTIVE INSULATION-INTERPOSED BETWEEN FUNCTIONAL INSULATION AND ACCESSIBLE

METAL PARTS

ALL INSULATION APPLIANCES-COPLETE OUTER CASE OF EQUIPMENT-NOT REQUIRED EARTHING

USE OF SPECIALLY DESIGNED EQUIPMENT IN HAZARDOUS AREAS

PPE

ELECTRICAL EQUIPMENTS FOR HAZARDOUS AREAS

FLAME PROOF- COVERS/ACCESS DOORS ARE DESIGNED TO WITH STAND THE INTERNAL EXPLOSION OF FLAMMABLE GAS/VAPOUR

INCREASED SAFETY-DESIGNED SUCH THAT TEMP. RISE IS 10 DEG. C LESS THAN THAT NORMALLY PERMITTED FOR THAT CLASS

NON SPARKING-ADEQUATE CREEPAGE AND CLEARANCES/SPECIALLY EMBEDDED ROTOR BARS AND RINGS/RESTRICTION OF SURFACE TEMP

PRESSURISED-ENCLOSED IN A HOUSING THAT IS MAINTAINED AT A HIGHER PRESSURE THAN ATMOSPHERIC BY AIR/INERT GAS

INTRINSIC SAFETY-DESIGNED SUCH THAT THE ENERGY /SPARK PRODUCED UNDER NORMAL/ABNORMAL CONDITIONS IS VERY LOW AND IGNITION WILL NOT TAKES PLACE-LOW VOLTAGE CIRCUITS

ELECTRICAL HAZARDS AND HOW TO CONTROL THEM

Electrical accidents are caused by a combination of three factors:

Unsafe equipment and/or installation

Workplaces made unsafe by the environment

Unsafe work practices.

HAZARD – EXPOSED ELECTRICAL PARTS

Cover removed from wiring box

CONTROL – ISOLATE ELECTRICAL PARTS

Use guards or barriers

Replace covers

Guard live parts of electric equipment operating at 50 Volts or more against accidental contact

CONTROL – ISOLATE ELECTRICAL PARTS - CABINETS, BOXES & FITTINGS

Conductors going into them must be protected, and unused openings must be closed

CONTROL – CLOSE OPENINGS

Junction boxes, pull boxes and fittings must have approved covers

Unused openings in cabinets boxes and fittings must be closed

Photo shows violations of these two requirements

HAZARD - OVERHEAD POWER LINES

Usually not insulated•

Examples of equipment that can contact power lines:

CraneLadderScaffoldBackhoeScissors liftRaised dump truck bedAluminum paint roller

CONTROL - OVERHEAD POWER LINES

Stay at least 10 feet away

Post warning signs

Assume that lines are energized

Use wood or fiberglass ladders, not metal

Power line workers need special training & PPE

STEP POTENTIAL Step Potential: Voltage between the feet of a

personWhen current is flowing from

the tower to the earth ground, the ground potential rises at the tower and a Voltage gradient will occur based on the resistivity of the soil, resulting in a potential difference between two points on the ground. This is called a Step Potential as it can cause voltage between a person’s feet.

TOUCH POTENTIAL Touch Potential: Voltage between energized

object and feet of a person If the ground connection

between the tower and the soil is high resistance (common with some soil conditions), the tower itself (and any conductive item touching the tower) can be energized. Touch potential is the voltage between the energized object and the feet of a person in contacT.t with the object.

HAZARD - INADEQUATE WIRING

Hazard - wire too small for the current Example - portable tool with an extension

cord that has a wire too small for the tool The tool will draw more current than the cord can handle, causing overheating and a possible fire without tripping the circuit breakerThe circuit breaker could be the right size for the circuit but not for the smaller wire extension cord

Standard Wire Gauge measures various sizes of wires

CONTROL – USE THE CORRECT WIRE

Wire used depends on operation, building materials, electrical load, and environmental factors

Use fixed cords rather than flexible cords Use the correct extension cord

Must be 3-wire type and designed for hard or extra-hard use

HAZARD – DEFECTIVE CORDS & WIRES

Plastic or rubber covering is missing

Damaged extension cords & tools

HAZARD – DAMAGED CORDS

Cords can be damaged by:AgingDoor or window edgesStaples or fasteningsAbrasion from adjacent materialsActivity in the area

Improper use can cause shocks, burns or fire

CONTROL – CORDS & WIRES

Insulate live wires Check before use Use only cords that are 3-wire type

Use only cords marked for hard or extra-hard usage Use only cords, connection devices, and fittings equipped

with strain relief

Remove cords by pulling on the plugs, not the cords

Cords not marked for hard or extra- hard use, or which have been modified, must be taken out of service immediately

PERMISSIBLEUSE OF FLEXIBLE CORDS

DO NOT use flexible wiring where frequent inspection would be difficult or where damage would be likely.Flexible cords must not be . . .

run through holes in walls, ceilings, or floors; run through doorways, windows, or similar openings

(unless physically protected); hidden in walls, ceilings, floors, conduit or other raceways.

GROUNDING

Grounding creates a lowResistance path from a toolTo the earth to disperseUnwanted current

When a short or lightingOccurs, energy flow to theGround, protecting you fromElectrical shock, injury and death

HAZARD – IMPROPER GROUNDING

Tools plugged into improperly grounded circuits may become energized

Broken wire or plug on extension cord

CONTROL – GROUND TOOLS & EQUIPMENT

Ground power supply systems, electrical circuits, and electrical equipment

Frequently inspect electrical systems to insure path to ground is continuous

Inspect electrical equipment before use

Don’t remove ground prongs from tools or extension cords

Ground exposed metal parts of equipment

CONTROL – USE GFCI (GROUND-FAULT CIRCUIT INTERRUPTER)

Protects you from shock Detects difference in current between the black and white wires If ground fault detected, GFCI shuts off electricity in 1/40th of a second Use GFCI’s on all 120-volt, single- phase, 15- and 20-ampere receptacles, or have an assured equipment grounding conductor program.

GROUND-FAULT CIRCUIT INTERRUPTER

CONTROL - ASSURED EQUIPMENT GROUNDING CONDUCTOR PROGRAM

Program must cover:All cord setsReceptacles not part of a building or structureEquipment connected by plug and cord

•

Program requirements include:Specific procedures adopted by the employerCompetent person to implement the program

Visual inspection for damage of equipment connected by cord and plug

HAZARD – OVERLOADED CIRCUITS

Hazards may result from: Too many devices pluggedinto a circuit, causing heated wires and possibly a fireDamaged tools overheating Lack of overcurrent protection Wire insulation melting, which may cause arcing anda fire in the area where the overload exists, even inside a wall

CONTROL - ELECTRICAL PROTECTIVE DEVICES

Automatically opens circuit if excess current from overload or ground-fault is detected – shutting off electricity

Includes GFCI’s, fuses, and circuit breakers

Fuses and circuit breakers are overcurrent devices. When too much current:

Fuses melt

Circuit breakers trip open

POWER TOOL REQUIREMENTS

Have a three-wire cord with ground plugged into a grounded receptacle, or

Be double insulated, or Be powered by a low-voltage isolation transformer

TOOL SAFETY TIPS

Use gloves and appropriate footwear Store in dry place when not using Don’t use in wet/damp conditions Keep working areas well lit Ensure not a tripping hazard Don’t carry a tool by the cord Don’t yank the cord to disconnect it Keep cords away from heat, oil, & sharp edges Disconnect when not in use and when changing accessories

such as blades & bits Remove damaged tools from use

PREVENTING ELECTRICAL HAZARDS - TOOLS

Inspect tools before use Use the right tool correctly Protect your tools Use double insulated tools

TEMPORARY LIGHTS

Protect from contact and damage, and don’t suspend by cords unless designed to do so.

CLUES THAT ELECTRICAL HAZARDS EXIST

Tripped circuit breakers or blown fuses

Warm tools, wires, cords, connections, or junction boxes

GFCI that shuts off a circuit

Worn or frayed insulation around wire or connection

LOCKOUT AND TAGGING OF CIRCUITS

Apply locks to power source after de- energizing

Tag deactivated controls

Tag de-energized equipment and circuits at all points where they can be energized

Tags must identify equipment or circuits being worked on

SAFETY-RELATED WORK PRACTICES To protect workers from electrical shock:

Use barriers and guards to prevent passage through areas of exposed

energized equipment

Pre-plan work, post hazard warnings and use protective measures

Keep working spaces and walkways clear of cords

SAFETY-RELATED WORK PRACTICES Use special insulated tools when working on fuses with energized terminals

Don’t use worn or frayed cords and cables

Don’t fasten extension cords with staples, hang from nails, or suspend by wire.

PREVENTING ELECTRICAL HAZARDS - PLANNING Plan your work with others

Plan to avoid falls

Plan to lock-out and tag- out equipment

Remove jewelry

Avoid wet conditions and overhead power lines

AVOID WET CONDITIONS

If you touch a live wire or other electrical component while standing in even a small puddle of water you’ll get a shock.

Damaged insulation, equipment, or tools can expose you to live electrical parts.

Improperly grounded metal switch plates & ceiling lights are especially hazardous in wet conditions.

Wet clothing, high humidity, and perspiration increase your chances of being electrocuted.

PREVENTING ELECTRICAL HAZARDS - PPE

Proper foot protection Rubber insulating gloves,

hoods, sleeves, matting, and blankets

Hard hat (insulated – nonconductive)

PREVENTING ELECTRICAL HAZARDS – PROPER WIRING AND CONNECTORS

Use and test GFCI’s

Check switches and insulation

Use three prong plugs

Use extension cords only when necessary & assure in proper condition and right type for job

Use correct connectors

TRAINING

Train employees working with electric equipment in safe work practices, including:

De-energize electric equipment before inspecting or repairing

Using cords, cables, and electric tools that are in good repair

Lockout / Tag-out recognition and procedures

Use appropriate protective equipment

SUMMARY – HAZARDS & PROTECTIONSHAZARDS

Inadequate wiring Exposed electrical parts Wires with bad insulation Ungrounded electrical systems

and tools Overloaded circuits Damaged power tools and equipment Using the wrong PPE and tools Overhead power lines All hazards are made worse in

wet conditions

PROTECTIVE MEASURES

Proper grounding Use GFCI’s Use fuses and circuit

breakers Guard live parts Lockout/tagout Proper use of flexible cords Close electric panels Training

ELECTRICAL SAFETY INSTRUCTIONS

No work should be taken up without obtaining SWP / AVI as applicable.

Ensure the isolations are carried out properly and equipment on which work is to be carried out is isolated from all supply sources no person shall work on any line or apparatus unless it is made dead by cutting off the supply at the concerned switch or switches near the line or apparatus. Main fuses, if any shall be removed and red tags shall be placed on the modules.

Before closing the earth switch / Earthing the system through earth rods, ensure that the live equipment has been isolated physically. Wherever possible. The circuit shall be checked for non-availability of supply through available HT/LT voltage test rods before touching the equipment.

ELECTRICAL SAFETY INSTRUCTIONS

When using a test lamp for checking any circuit, the glowing of the lamp positively indicates presence of working voltage in the circuit, but the converse is not correct. A test lamp not burning may reduce to insufficient voltage to light the lamp or due to defect in the connections or in the bulbs or even due to points tested across being at the same potential etc. Hence where ever possible use the HT voltage test Rods / Testers etc for ensuing of the circuit is dead. In case of using test lamps, to avoid flash over in case of touching across phases by mistake.

All safety devices & tools shall be inspected at periodical intervals to ensure that they are maintained in perfect working condition.

No repairs of any kind shall be done on live equipment, except by authorized persons complying with precautions laid down for the work.

ELECTRICAL SAFETY INSTRUCTIONS

Following instructions shall be followed while working on TGs, GTs & UATs. Ensure the Generator is at rest unless special permission has been obtained to carry out the work

on line for example the brushes checking / Replacement as per schedule. Ensure safety while working on line like wearing gloves, reducing the load on Generators etc.

Ensure the field circuit is isolated.

While working on power / distribution transformers, ensure the following

Ensure that both primary and secondary circuit breakers and isolators are opened..

Prevent back feed: While isolating transformers to which potential transformers are connected, the potential transformers shall be isolated and low voltage fuses with drawn to prevent the possibility of the transformers being made live through back feed.

The Transformer shall be isolated from all common neutral earthing equipment from which it may become live. This does not require the disconnection of solidly earthed neutral on which work is to be done.

ELECTRICAL SAFETY INSTRUCTIONS

While working on CTs ensure the following. The secondary circuit of current transformers must be connected

to ground at all times when they are in service.

The secondary circuit should never be open circuited while in service when any instrument connected to a secondary circuit has to be removed, replaced or freshly introduced the secondary circuit should be shorted temporarily at an appropriate place before the point of work. After the work is over, all open circuits, if any, caused during the job should be closed & then temporally shorting should be removed.

The primary side of current transformers should not be approached unless these transformers are completely disconnected from circuit and effectively earthed

ELECTRICAL SAFETY INSTRUCTIONS

While working on PTs ensure the following:

The primary parts of PTs should not be approached unless they are completely disconnected from the circuit and effectively grounded.

Fuses on HT side should be replaced after ensuring isolations &

valid SWP and after discharging properly by earthing in replacing LT fuses, operator should shield his eyes as far as possible flashes when fuses are common network or paralleled on LT side, caution should be exercised to ensure that there is no possibility of back feed.

ELECTRICAL SAFETY INSTRUCTIONS

While checking testing street lighting , the main equipment and fixtures should always be considered as live parts unless they are held off from all sources of supply and effectively grounded.

All street lighting work of any descriptions on energized lines should be done wearing gloves and taking all necessary precautions.

Use safety devices and special tools like rubber gloves,

rubber mats, safety belts, insulated hand tools etc. wherever required.

ELECTRICAL SAFETY INSTRUCTIONS

• While carrying out works on Batteries ensure the following.

The storage battery room should be always securely locked and should have adequate ventilation.

Do not smoke in battery room and do not carry any necked flame or use of heaters that produce sparks.

Don’t block the passages between the racks in storage battery room or to store any inflammable materials inside.

Protective appliances like acid proof aprons, gloves, boots and eye glasses must

always be worn before starting to do any work concerned with the battery. All contains with electrolytic solution and distilled water shall be identified by

properly marking. While handling acids, a second person should be close at hand ready with

neutralizing solution. Ensure adequate ventilation in battery rooms.

SUMMARY• Electrical equipment must be:– Listed and labeled– Free from hazards– Used in the proper manner

• If you use electrical tools you must be:

Protected from electrical shockProvided necessary safety equipment