tpl electrical safety230311

Kavoori Consultants 1

ELECTRICAL SAFETY AUDIT

K. R. GovindanKavoori Consultants

22, Janakiraman street,West Mambalam

Chennai, 600 033.Tele: 044 24846139


SCOPE OF SAFETY AUDIT

Inspection of the electrical equipments and components of a system for

safe installation, adequacy for normal load and fault levels, safety for normal operation


System equipments and components:

High tension power incoming feeder, isolator and breaker arrangements

Power and distribution transformers Primary power distribution system, Secondary bus duct / cable arrangements Secondary panel, breakers Indication and annunciation arrangements



Grounding arrangements Earthing stations and system, Feeder arrangements, Neutral grounding and equipment grounding

effectiveness, Cables galleries, tunnels, ducts, laying

arrangements and fire protection Distribution substations M V and LV switchgear and MCC stations Battery bank and battery room


System equipments and components: Grounding arrangements Earthing stations and system, Feeder arrangements, Neutral grounding and equipment grounding

effectiveness, Cables galleries, tunnels, ducts, laying

arrangements and fire protection Distribution substations M V and LV switchgear and MCC stations Battery bank and battery room



Lighting distribution:Lighting panels

Fire alarm and mulsifier systemsElectrical installations in Process Areas Electrical installations in Utilities, Effluent and Water Treatment Plants, Investigation in to recent electrical accidents and cause analysis,



Fire water system and Main and jockey pumps for their control systems,

Static protections employed in hazardous material handling areas,

Selection of enclosures for electrical control and

power equipments in hazardous areas, Emergency stand-by power:



Records

Electrical failures records and cause analysis.Operation, Maintenance of these equipments, Preventive and predictive maintenance practices and



routine tests carried out on control gears from the safety angle of view,

Compliance with Safety and Statutory Requirements

Hazardous area classification and equipment compliance.


Operation and maintenance practices

Permit work clearances and procedures Safety precautions and practices Normal and emergency operation and

procedures Compliance with Safety and Statutory

Requirements:


Personnel protective appliances and implements:

Adequacy of protective gears available Adequacy of metering and measuring

equipments First aid and safety practices


Fire and safety:

Electrical Fire fighting equipments and systems

Fire water and pumping systems and their controls.


OBJECTIVES OF ELECTRICAL SAFETY AUDIT:

To assess the safety of equipments:From damage during normal operation.Capability of the protective system to protect the equipment’s in the event of electrical faults.


To assess the safety of the personnel:

Are the operating and maintenance personnel aware of electrical hazards?

Is statutory regulation fulfilled? During emergencies also?

(Power failures, Electrical fault)


To assess the System’s capability:

Is the system adopted safe for maintenance personnel for carrying out electrical job Safely?

Does the system adopted satisfies statutory regulations (Maintenance practices)

Does the system provide Review mechanism for checking adequacy of electrical safety?

Does the system provide amendment of Safety practices & Communication with relevant personnel?


Other aspects:

Assessment of the existing systems’ adequacy, strength and weakness,

Is the Electrical System adequately protected against external causes?

Is there a relevant safety manual available on operation and maintenance and emergency procedures?


Emergency Preparedness:

Adequacy, suggestion for improvements. Call for site employees suggestion Involve them in the task Educate them Create awareness and constant

consciousness


ELECTRICAL SAFETY

MOST IMPORTANT ESPECIALLY FOR PETROCHEMICAL INDUSTRIES


ELECTRICITY IS

A good servant, but

a bad master

You control it, it will serve you nicely

Do not allow it to control you

Electricity excuses nobody

Accidents do not happen; they are caused

krg

Updated.


ELECTRICAL SAFETY

ELECTRICITY Convenient, clean, useful source of energy Easily transformed into other energies Mechanical, chemical and heat Easily produced Conveniently transmitted to long distances

without much loss


BUT POTENTIALLY A SOURCE OF GREAT DANGER AND HAZARD!

1. Shocks, some times fatal

2. Injuries and burns

3. Permanent deformation of the victim and

4. When used in a hazardous atmosphere, electricity may be a potential source of ignition.


Much development taken place in equipment usage, designed to be safe.

But not proof against misuse and neglect Understand hazardous Do not take risk, in doubt ask Electricity does not excuse any one A good servant but a bad master.


Electricity is:A Good Servant – But a bad master

Six Golden rules:1. Follow all safety rules2. Adhere To established procedures3. Use proper control gears4. Never take anything for granted5. Always be alert6. Keep your mind on the job.

You control electricityIt will serve you nicely!

Do not allow it to control you!


Accidents do not happenThey are caused

Due to Ignorance Negligence Inadvertence Third person’s ignorance Not using safety gears Not having enough knowledge or experience Over confidence due to long experience



Not checking the system for

* Alternate power source

* Residual charges

* Low voltage reverse feeding

* Ring main system

* Multiple sources



Inefficient or no supervision Non co-operation from co-workers Consuming intoxicating drinks,

substances Family problems Natural calamities Fatigue due to lack of rest



Lack of proper display of caution boards

Not checking the conditions of safety gears

Improper fire extinguishing equipments

Improper protective equipments Lack of maintenance of safety gears


WHAT IS ELECTRICITY?

AMPERES?VOLTS?WATTS?

FLOW OF CURRENT AMPERES

WITH POTENTIAL DIFFERENCE VOLTS ACROSS A RESISTANCE OHMS

FLOW OF CURRENT GIVES POWER WATTS

POWER FLOWING FOR A PERIOD ENERGY


How electricity works for you?

4AMPS = 240VOLTS/60 OHMS

VOLTAGE MAKES CURRENT FLOW

THROUGH A RESISTANCE. `




THROUGH A RESISTANCE.

240 V 960W

60 (Heater)

4 AMPS

4 AMPS




THROUGH A RESISTANCE.

240 V 960W

60 (Heater)

4 AMPS

4 AMPS

Voltage and current


4AMPS GOES TO HEATER

4AMPS RETURNS BACK

WHERE FROM 960W POWER CAME?

HOW ELECTRICITY WORKS FOR YOU ?


WATER FROM HIGHER LEVEL

DOES MORE WORK

MORE HEIGHT - MORE ENERGY

CALLED POTENTIAL ENERGY




WATER GOES THRO’ A TURBINE

GIVES THE ENERGY - OR DOES WORK

BUT IT IS NOT CONSUMED! CURRENT - AMPERE - SAME LIKE WATER

DOES WORK AND RETURNS



POTENTIAL DIFFERENCE - VOLTS

LIKE HEIGHT - MORE VOLTS MORE WORK

1 AMPERE FROM 1 VOLTS - 1 WATT POWER

WATT (POWER) = VOLT X AMPS.(P. D.X CURRENT)


WHAT IS POWER? WHAT IS ENERGY?

ENERGY IS QUANTITY OF WORK DONE POWER IS RATE OF DOING WORK. 100LTRS OF WATER TO BE BOILED

1KW HEATER TAKES 2HRS. 2KW HEATER WILL TAKE 1HR.

ENERGY = POWER X TIME.

KILO WATT X HOUR = KILO WATT HOUR =K W hr


ELECTRICITY - CONTROL FOR SAFETY

Proper control of electricity assures safety Electrical power should be isolated before

development of a hazardous situation Imminent fault development to be foreseen and

preventive action taken Only control – faulty circuits should be isolated

1. Immediately and

2. Automatically


Immediate isolation of faulty section; How?Possible to watch continuously?

MAJOR PROBLEM -Insulation failureHAZARDS Shock to personnel, Fire hazardsTotal equipment damage, Power system collapseMechanical damage

Fault location impossible

ELECTRICITY - CONTROL FOR SAFETY


How to monitor continuously & isolate automatically?

Make electricity do it; but, How?

Make fault current grow quickly to a large value

and actuate protective isolating devices.

Good, but how?

Current will flow from Phase to neutral or, Phase to phase


FAULT or INSULATION FAILURE

Provide short circuit or low resistance pathsfor phase and neutral (or) phase and phase

PHASE TO PHASENo hazard! The breaker or fuse isolates faulty section or

equipmentBETWEEN LIVE PARTS AND BODY

HAZARDOUS!People work on equipment, in contact with them

Insulation failure results in electric shock or injury to them!SOME TIME FATAL!


CONNECT BODY TO GROUND SOLIDLY

Insulation failure (fault) makesthe fault current grow to a large value;

actuate protective devices andisolate the faulty equipment or line

IMPORTANT! SYSTEM NEUTRAL SHOULD HAVE BEEN

GROUNDED!

If ground resistance high, low fault current;protective system not operates;

higher fault voltage drop and greater hazard


NEUTRAL GROUNDINGNeutral not grounded; but equipments grounded

A

C B

a

c b

MOTOR NO.1

MOTOR NO.2


NEUTRAL GROUNDING

A

C B

a

c b

MOTOR NO.1

MOTOR NO.2


PROPER NEUTRAL GROUNDING ASSURES

Reliability, Safety and Equipment protection

Power system transformer neutralConnected to earth by Two copper or G. I strips to exclusive neutral electrode, to earth bus

Earth electrode resistance to beLess than 2 ohms

Transformer and equipment bodyTwo connections to earth bus


WHAT IF NEUTRAL NOT GROUNDED?

No current flows to ground.Another fault - another equipmentMay be another phase

All faults - high resistanceLow current- no automatic isolation

Full phase voltage, Danger to human life415 V SHOCK FATAL!

Fault current through available pathFire hazardSputtering ground


CONTROLING ELECTRICITY

Mainly isolation of faultily equipment or circuits

To avoid hazards Isolation should be

Automatic, Very fast And very accurate

Protective elements can protect only equipments and systems and not human beings

Human heart is highly sensitive to passage of electrical current


CONTROLING ELECTRICITY

Controlling elements are

1. Fuses

a. Wire fuses

b. Enclosed fuses

c. HRC fuses

2. Circuit Breakers

a. Automatic circuit breakers

b. Fused switches and switch fuses

c. Manual isolators


PORTABLE EQUIPMENT Single phase Use 3 core cable

Three phase use 4 core cable

Care of safety appliances:Rubber gloves /gauntlets

Rubber matFace shield / goggles

Discharge rodsaprons

Testers/test lamps Multi-meters


BALANCED LOAD Neutral Current

Y

B

N

R5 A 5 A 5 A

5 A 5 A 0 A


The Resistance of Earth System: Major sub stations: 1 OhmOther sub stations: 2 OhmsDistribution transformer stations 5 Ohms Earth connection should be able to carry at least ½ Sec.

Area of Cross Section: Fault Current 15,000.


Electrical Safety

Permit System:Modern industries switch boards, M. C.C.S, distribution boards located ~ Away from the equipments connected ~ In separate rooms or enclosures

Not in direct view of equipments.Only authorized persons can enter or operate.

Good practice!


Many crafts work on the same equipment

But controlled equipment not seen or in the vicinity

Fool proof method required to assure safety of

1. Persons working

2. Equipments against damage.


Permit Systems:

1. Work permit system:

Line clear: Written format (permit) signed by issuer after switching off power.

Issuer locks switches

Receiver signs and returns permit after work is completed.

Issuer cancels permit & energizes line-equipment.

Not very fool proof - Many crafts involved.


2. Tag Out System:

Better system

Tag with detachable portions with non detachable duplicates.

Issuer signs duplicate,issues detachable portion to craft leaders

Each craft leader returns detachable portion signed after work is completed.

After receiving all issued portions and getting signed in the duplicates. issuer removes tag and energizes equipment - line.


Eqpt No: 1.Plant:Issuing authority:Receiver: Time:Date:Approx duration:Others:

Eqpt No: 1.Plant: Issuer:I declare that my men and materials are clear of the above equipment and it can be energized. Date: Time:Receiver:

Non-detachable portion: Detachable portion:

Eqpt No: 2.Plant:Issuing authority:Receiver: Time:Date:Approx duration:Others:

Eqpt No: 2.Plant: Issuer:I declare that my men and materials are clear of the above equipment and it can be energized. Date: Time:Receiver:

TAG – OUT SYSTEM


Open Position


LOCK OUT SYSTEM

Closed Position


ELECTRIC CURRENT EFFECT ON HUMAN

Less than 0.5 milli amps – not felt

0.5 to 12 milli amps – painful, causes start

Above 12 milli amps – muscles contracts

Possibility of holding on and heart stopping

Less current more time to stop heart

50 milli amperes for 200 milli seconds can stop the heart


DO NOT TAKE THIS AS A GUIDELINE!

High skin resistance limits the current

Cuts skin and dampness will reduce the resistance

Cautions – wet places very dangerous

Good bonding and earthing needed


PRECAUTION AGAINST ELECTRIC SHOCKS

1. Good electrical installation and maintenance practice

2. The use of low voltage or High Frequency above 15 kHz.

3. The earthing and bonding of all metal work which might become live and

4. The installation of special protection such as armoring, screening, and earth leakage circuit breakers.


SHORT CIRCUIT CURRENTS

Short circuits causes 20 times normal currents

1000 kVA transformer gives 30,000 ampere Agonizing injuries to the human, fuses metal,

ignite flammable liquid and vapors.


MICROWAVE OVENS

Articles in microwave ovens are heated by microwaves.

The microwaves are at the frequency of approximately 2.45GHZ

A magnetron microwave generator is employed to produce microwaves

These waves cause molecules of water and other compounds to rotate or vibrate


MICROWAVE OVENS

The vibration creates heat which cooks the food or boils the liquids

Efficiency: A typical oven of 1100 Watts delivers 700Watts

microwave energy 400 Watts dissipated as heat by the wave generating

components


MICRO WAVE OVEN - HAZARDS

Liquids in container with smooth surface can super heat.

Reach temperatures above normal boiling point without boiling

Boiling can start explosively when the liquid is disturbed that is when taken out from the container.

Closed containers and eggs can explode due to steam generation



Tin foil, aluminum foil, ceramic decorative metal can cause sparks

RADIATION: Exposure to micro wave radiation is injurious

to health Legal limit of radiation is 1 mW/cm2, at 5 cm

from a new oven For used oven five times this limit is

acceptable



Mandatory requirements for radiation leakage limitation for ovens produced after 1971;

Less than 5 mW /cm2, approximately at two inches of the surfaces of the oven

Micro waves are not as bad as X-rays or ultra violet radiation.

The oven front glass window is made up of special screen which blocks micro wave radiation leakage

Shut off the oven if any damage to this noticed This should be immediately repaired


MICROWAVE OVEN- CONSTRUCTION

The cooking chamber is a Faraday cage enclosure; Prevents radiation from escaping through. Oven door - glass panel for easy viewing, But with a layer of conductive mesh for shielding. Size of the mesh is much less than the microwave

radiation wavelength of 12 cm, The radiation can not pass through the door But visible light, with much shorter wavelength, can

pass through the door.


NEUTRAL AND GROUND (Continued)

Never, never use ground wire as neutralNeutral conductor carries return or unbalance currentBut, earth conductor carries fault current only.Earth conductor as neutral, will carry current- Any loose connection or high resistance joint, voltage builds upEquipment bodies, earth bus give shock; Arcing, fire hazards etc.


NEUTRAL AND GROUND (Continued)

Our System Is “Neutral Grounded System” or Simply “Grounded System”At all generating, distribution points, the neutral is grounded.That is, the neutral is grounded at:Power transformers And generators of E.B., Distribution Transformer and Generators.System parameters to be:

Phase to Phase Voltage 415v Phase to Neutral Voltage 240v Contact Voltage 240v

Insulation Failure Less Hazardous.


EARTH ROD TOP CLAMPED TO EARTH BONDING TAPES.


Code of practice for grounding: Guide lines: substations: 1. Sufficiently low neutral to ground resistance

2. Gradient control on the surface, equipments to ground or across two parts that will come in

contact simultaneously.

Touch potential or step potential:

Should not exceed 55 volts

3. For grounding calculation: 3secs.


4. Grounding conductor: Around the S.S. Perimeter ~ mesh of 4m x 5m

5. No of ground rods: Max. Ground fault current 500. Should be distributed entire grid.

6. Min. Size 6 S.W.G. G. I. Wire

7. Size of EQ. Size of copper: Short circuit current in Amps sq”. 15000 X n n = number of parallel paths..(Current Density : 1500amps/sq”. For 30secs)


8. Earthing conductors should never be * Run in metal conduits

* In cement troughs Etc.

Recommended Size of Earthing Conductor: Fault Current Size of Cu. Earthing Cond.K.A. Cross section Dimension Sq. Inch Not exceeding 22 0.2 1 ½ X 3/16“

30 0.3 1 ½ X 3/16” 44 0.5 2 X 1/4

Acceptable Temperature rise: Due to passage of fault current = 450oC.


ELECTRICITY AND HUMAN REACTION

Which is more dangerous?

Alternating Current or

Direct Current ?

AC more dangerous.

DC welding plants lesser risky;

90 volts AC welding machine dangerous

Burn hazards


CURRENT AND FREQUENCY

Higher frequency lesser risk 12 to 13 milliamps at 50 HZ cause hold on At 500 HZ this current no effect But higher frequency deeper the burn Micro exposure cause cataracts High frequency does not cause paralysis.

Electrical frequency - effect on human


Electrical frequency - effect on human

THRESHOLD OF FEELING: DC 3 milli ampere; AC 50 HZ – 1 milli ampere; 9 milli

ampere at 10 KHz DC applied to nerve fibre – muscle moves once, then

releases 8 pulses per second – muscles stay contracted Hence, 50 Hz cycle so very dangerous Current through heart stops Death follow if heart stopped between 3 to 8 minutes


HUMAN HEART

4. Heart stops completely – cardiac arrest

Failure of heart to deliver oxygenated blood to the head – irreversible damage – death follow in a very short time

Dry skin high voltage, severe burn Not necessary electrocuting the victim Low voltage at wet or sweating skin cause

death No evidence of burning.


If path of the current is through chest Most fatal accident occur at consumer voltages In mechanical terms the human heart is a compact

280 g assembly, comprising two separate 2-stage displacement pumps working in series and in synchronism. It has a continuous rating of about 4-5W and a short-time rating of at least 20W. Its ‘specification’ requires it to be

Self-powered by extraction of energy from the pumped medium (I.e, by using some of the oxygen from the blood)

Completely maintenance-free Capable of continuous operation at 6—74

strokes/min for at least 600 000 h with 100% reliability


Self-regulating by nervous control from the brain.

Two ways heart upset by passage of electric currents

1. Stop completely (I.e) Cardiac arrest2. Heat muscle fails contract in unison Start tremble or twitch No effective pumping action; cardiac

fibrillation or ventricular fibrillation If not quickly rectified can cause death No burning – survivors recover completely.


THE HUMAN HEART

Chambers and ValvesThe heart is divided

into 4 chambers: 1. Right Atrium (RA)

2. Right Ventricle (RV)

3. Left Atrium (LA)

4. Left Ventricle (LV)


Schematic diagram of the function of the heart

1. Vena cava (carrying blood from capillaries and liver to the heart via the veins)

2. Right and left atria (reception vessels)3. Right and left ventricles (main pumps)4.a. Tricuspid valve (non-return valve)4.b. Mitral valve (non – return valve) 5. Right and left auricles (priming pumps)6. Pulmonary arterial valve (non-return

valve)7. Pulmonary arteries (supply to the

lungs)8. Pulmonary veins (supply from lungs to

heart)9. Aortic valve (non-return valve)10. Aorta (main discharge line from the

heart to the body)11. Heart muscle or myocardium (pump

drive)


THE HUMAN HEART

A hallow cone shaped muscle located between the lungs

2/3rd is to the left of the middle line of the body and 1/3rd to the right

Heart muscle contracts (Systole), pumps blood out of the heart

Right side of the heart collects oxygen poor blood from the body

Pumps to lungs In lungs blood picks up oxygen release CO2

Left side collects oxygen rich blood and pumps to the body


THE HUMAN HEART

Cells through out the body get oxygen to function properly Phase maker cells create electrical impulses and the heart

beats Heart beat rate changes as we age:

Newborn 1303 months 1406 months 1301 year 1202 years 1153 years 1004 years 1006 years 1008 years 9012 years 85Adult 60 - 100


HEART THE PUMP – SPECIFICATIONS

A compact 280 g assembly Comprising two separate 2 –stage displacement pumps working

in series and in synchronism Has a continuous rating of about 4-5W and a short-time rating of

at least 20 W An average heart pumps 2.4 ounces (70 milliliters) per

heartbeat Or, pumps 1.3 gallons (5 liters) per minute Heat of 70 years old has pumped 48 million gallons

(184,086,000 liters)! Self-powered by extraction of energy from the pumped medium

(I.e. by using some of the oxygen from the blood) Completely maintenance-free Capable of continuous operation at 60-74 strokes /min for at

least 600 000 h with 100% reliability Self-regulating by nervous control from the brain.


CATHODIC PROTECTION

Locations – oxidation reaction Metal attains a local positive – anodic corrosion Reduction reaction – cathodic corrosion Soil made positive – with respect to metal surface Anodic corrosion reduced, cathodic corrosion

increases Impressed voltage cathodic protection Protected structure


CATHODIC PROTECTION

All points negative with respect to soil or water

Depends Upon Anode location and distance from the structure Electrical resistance between various parts of

the structure Differing surface condition of the structure Non uniformity resistivity of ground Between anode and structure


CODES OF PRACTICE (COP)

Marking code: Ex o – Oil immersion Marking code: Ex p – Pressuried apparatus Marking code: Ex q – Powder/sand filling Marking code: Ex d – Flame proof enclosure Marking code: Ex e – Increased safety Marking code; Ex ia and Ex ib ( ia is safer than ib) –

Intrinsic safety Marking code: Ex m – Encapsulation Marking code: Ex ia or Ex ib – Intrinsically safe

systems Marking code: Ex N – Type of protection N Marking code: Ex s – Special protection


COMMON UNSAFE PRACTICES

Wiring: Working with the mains ON Replacing an open fuse Providing switch in neutral line instead of phase line Working with wet feet or hands Opening a bras lamp-holder which may be live Unprotected socket outlets

Portable electrical appliances Ineffective or no earthing Working on live appliances without insulated tools or gloves Damp floor or feet.


STATIC ELECTRICITY

Electricity from word elektron, Greek for amber Created when two surfaces in contact separate Greater effect if sliding Most effective in insulating material because charges

cannot move directly to recombine Conductors – charges recombine and do not build up Starts with one volt-rises to several thousands volts


STATIC ELECTRICITY

Fine powders Very much subject to static accumulation Become highly charged whenever poured, sieved, mixed,

ground or blown Transfer the charge to the container If container earthed the charges leaks away

Chargers in Liquids: Oils and explosive liquids = non conducting retain charges Charges in liquid generated to dangerous potential level when Liquid flowing through a pipe


STATIC ELECTRICITY

Liquid flowing through a fine mesh filter Undissolved or immiscible particles moving within the liquid The presence of two different liquid phases Mist, spray or droplets moving through a gas or falling within a

vessel

Charges in Gases Charging process not like liquids or solids Gets and streams or containing particles, solid or liquid

generates charge from or impart charge two other items of the equipment

Release of CO2 or LPG cause considerable cooling – formation of CO2 snow and LPG mist – dangerous from static point of view


STATIC ELECTRICITY

Cleaning by compressed air – disturbed dust and spray present possible hazard; all nearby metal object should be earthed

Particle free – explosive gas will not produce static charge – but readily ignited by a very small low energy ESD

High pressure spray painting may generate potentials of kilo Volts

Hand held spray gun (1) possible high voltage shock (2) presence flammable atmosphere, danger of fire explosion


LIGHTNING - STATIC ELECTRICITY, Contd.,

Rate of rise of discharge reach 200 kA/s Equivalent to 100 mega hertz., Inductance H, a bend or a loop in the conductor;

high impedance Cause high potential and jumping across Similarly a very low capacitance – very low

impedance discharge reflected in adjacent metallic objects

Selections of pipe line are electrically isolated Remain pipe work bonded at site Isolating flanges may have spark gaps

tpl electrical safety230311

Technology

electrical system

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safety of equipments

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