Electrical Hazards and Safety

Compiled By: Arvind Thukral

Self Introduction

Name - Arvind Thukral

Qualifications:

B.E. (Electrical) REC Bhopal 1969

FIE

MAM (Mumbai University) 1986

Certified Energy Auditor - 2007

Self Introduction

Experience:

Tata Mills, Mumbai (Textile) 7 years (1970 76) in Electrical / Utilities HLL / Unilever 5 years Maintenance 10 years in Electrical Design, installation and commissioning for new factories. Central support to factories.10 years as Factory Manager in various businesses.

Self Introduction

Experience (continued..)Since Retirement in 2002 involved in Electrical Safety Audits of factories / Offices HUL, Cadbury, Bilcare Limited, United Breweries, Cipla, Syngenta, Nestle, Britannia, ITPL, Gokaldas Exports. Electrical Safety Initiative in HUL.Electrical Engineering Training various levels

Self Introduction

Experience (continued..)Since Retirement in 2002 .. Consultancy in Electrical Engineering HLL, Universal Capsules, Cadbury, Syngenta, United Breweries Limited..

Energy Saving Initiatives:BilcareGokaldasHUL

Electrical Hazards and Safety

Is Electricity Dangerous?

Electrical Hazards

What are the Hazards?

Contact Hazard with Electricity

Earthing Helps.Current stopsSafe to touch

Fuse BlowsEquipment Earthed6 A Fuse / MCBCurrent - Hundreds of Amp

Earthing is cut here!Equipment EarthedFuse Does not BlowCurrent is 240 miliampereHuman Body Resistance 1000 ohm 6 A Fuse / MCBResult - Electrocution

Electrical current through human body & its effectWhat happens when current passes through human body: Is DC Safer?

Electrical Hazards

Electrical HazardDefibrillator in Use

Electrical Hazard Contact electrical burns. The knee on the left was energized and the knee on the right was grounded.

Electrical HazardsArm with third degree burn from High Voltage Line

Contact HazardsHence there is a need for user protection through highly sensitive, fast tripping devices based on detection of the Residual Current to earth through human body or otherwise.

For human safety standardize on a device which will detect 30-ma of residual current and trip in 30-ms (BIS limit 200 ms).

Residual Current ProtectionPrinciple of operation of a Residual Current Device.Circuit is Safe nowSensitivity 30 ma

Residual Current ProtectionPrinciple of operation of a Residual Current Device.Circuit Disconnected - Person is safeSensitivity 30 ma

Electrical Hazards Use of ELCBsConsider ELCBs for the following circuit applications

All 3-phase and single phase plug points.All portable tools,Welding machines, movable plant equipment such as conveyors, packing / wrapping machines , metal detectors, hydro-pack and metering pump units etc. not permanently grouted on a 24*7 basis, light fittings, ceiling fans, air circulators, stitching machines etcWhere maintenance of earthing is in doubt, particularly for the high-risk areas like off site locations, project sites, contractors sheds, temporary installations, trolley-mounted pumps/equipment etc

Electrical Hazards. contdShort Circuit HazardsInsulation failureUnintentional contact of two/three phases (low resistance path) or phase and earthEnergy released is proportional to the square of current and proportional to the time it flows.Released energy radiates heat and causes flash, burns and damages equipment.

Flash Can kill

HV Isolator Arc

Transformer Failure - Movie

Damage Due to Short Circuit

Damage Due to Short Circuit

Electrical HazardsElectrical Burns on Hands and Arms

How unsafe electrical installations affect safety of personnel and plant

Low energy level faults leading to fatalityCaused by human contact (direct or Indirect) with live parts in the event of insulation failure / ineffective earthingShock arising out of electrical current passing though human body (heart) : current at 30 mA for more than a few mS has fatality potential. Higher the current, lesser the time available for disconnection.

High energy level faults in damaged equipment / burns/ fatalityInsulation failures can result in a short circuit current (in kA) causing flash / fire / explosion, damage equipment and/ or cause serious burn injuries to personnelHigher settings of relays / high fuse ratings increases time to isolate faulty circuits, higher energy dissipation and corresponding damage

Electrical Hazards

How should these be tackled?Low energy level faults

Electrical Hazards How to protect?

How should these be tackled? ( Contd.)Low energy level faultsProvide Enclosures with interlocksShrouds effective insulationBarricadeProper PTW systems & management of change procedures by competent persons/agenciesEnsure effective earthing at all times design of earthing systemNo live working should be allowed.Provide ELCBs of 30 mA sensitivity in mandated hazardous locations and ensure their reliabilityEffectively monitor higher hazard usage points (plug points) and equipment used at these points (welding machines, hand tools, mobile units etc)Use safer voltages (less than 50 V / 25 V), wherever possibleUse of unearthed system

Electrical Hazards How to protect?

How should these be tackled..?

High energy level faults

Never allow live workingUse PPE Nomax suit / shieldReliable and proven design of electrical switchgear / equipment Rigour in maintenance practices to reduce possibilities of insulation failureProvide reliable, closer protection for electrical circuits using relays - maintain their reliability at all times, through tests & checks.

Electrical Hazards How to protect?

Electrical Hazards - FireElectrical Overload causes Fire

Electrical Hazards - FireLoose Connections in switch gearsLoose JointsHigh earth fault current in flameproof areaStoring flammable material near Distribution Boards

Electrical Hazards - FireHow to tackle Fire Hazards:Improved maintenanceCheck switchgear connections regularlyBarricade DBs / MCCsThermographyAvoid use of jointed cablesFor flameproof areas use special equipment to reduce earth fault currents.

Electrical HazardsThese measures are only preventive.Consider:Lack of (proper) maintenance,CarelessnessImproper earthing connectionsBypassing safety interlocks mechanical / electrical.Normal (or abnormal) wear and tear of insulation; for example, aging and abrasion of connecting leads,Accidental contact,Immersion in water, etc. - a situation in which insulation is no longer effective.

Electrical Safety While Working On Electrical EquipmentAlways ensure positive isolation before handling any electrical equipment.Earth the terminals to be worked uponNever work on liveEnsure shrouding of live partsSwitchgear terminalsOutgoing terminalsLOTOUse insulated hand gloves.Use double insulated hand tools drilling machines, grinders etc. (Square in Square)

Electrical Safety While Working On Electrical Equipment Contd.Safe touch voltages:50 V for dry areas25 V for wet areasControl voltage 110 V (+55, 0(E), -55) Use safety shoesUse of masks / suitsAvoid static electricity built up. Antistatic floors....Licensing issues instrument technitians?Designing issues Tripping to take place within safe limits for 220/230 VFor touch voltage limits of 25 V 50 msFor touch voltage limits of 50 V 170 ms

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