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PresentedBy

PresentedBy PresentedBy PresentedBy-

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Objective of the session

Create an awareness about importance of electrical safety in

ur day today activities , in industrial applications and in
ur day today activities , in industrial applications and in

construction Industries .

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Topics Coverd

Competence Electrical Hazard Earthing System Documentation Guidelines for Maintenance & Testing Guidelines for Maintenance & Testing Portable Equipment Using PPE Cable selection Criterion and precautions Statutory Norms

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Competence Competence

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Purpose of competence

Deployment of right workmen for a particular job to enhance productivity complying safety. Development of supervisors and workmen skill by various means . Development of supervisors and workmen skill by various means . Development of a robust process which enhances the skill set of the people . Inculcate a culture for safety.

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Competence

Technical Statuatory

Competence Development

On Field Training Class Room Training Training by OEM Workmen Development through CSR activities Electrical Licence for Workmen Supervisory Licence

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Classification of Licence for supervision and execution

LT licence up to 415 V
H.T Licence up to 33 KV
EHT licence beyond 33 KV
Licence for HT jointer
Licence for HT jointer
Licence From Director General of Mines

& Safety Licence can be obtained

At state level
At national level

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ElectricalHazard

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MINIMUM SAFE CLEARANCE VALUES

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Shock Protection Measures

Isolation Current limitation Low voltage Double insulation Earthing Earthing Over Current Protection Devices Residual/Leakage Current Protection Devices

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Isolation Transformer

Power can be tapped from isolation transformer Avoids shock between earth and phase

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Low Voltage

24V hand lamps. By earthing the mid point of a single phase transformer, the line to earth voltages are reduced to 115V while the full supply(230) is available to the apparatus.

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Relays are the devices which sense the abnormal conditions from the power system and take trip decisions.

Overcurrent protection devices

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RCCB WORKING PRINCIPLE

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Application of RCCB

Domestic & Industrial Lighting
Welding Machine
Refrigerator
Hand Tools

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ELR WORKING PRINCIPLE

Normal E/F protection = Ir+

Iy+ Ib+ In=0. During E/F , the residual current flows through neutral and in-built E/F release in CB

perates .

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Earthing Earthing

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Purpose of earthing

Prevention of electrical shock. Allowing passage to electrical fault current through least resistive path. Sensitive Earth fault protection Safety of the electrical system and equipment's.

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Industrial Guidelines for earthling

The combined Electrical earthing value of electrical system to be less than 1 Ohm
Electronic earthing for PLC /DCS should be different from electrical earthing
The value of the electronic earthing should be less than 1 ohm
The value of the electronic earthing should be less than 1 ohm
Neutral of transformers should be separately earthed and should be able to isolated.
For residential applications the voltage between neutral and earthing not to exceed 5V.
All the equipment's to be earthed at two points

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Methods of earthing

Deep bore earthing for soils having more resistivity

Use of good earth
Use of chemical earthing in rocky soils.

Earthing grid formation by MS rod or G.I flats

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Sub-station Grounding Step Potential

Step potential is the step voltage between the feet of a person standing near an energized grounded object. near an energized grounded object.

Touch Potential

Touch potential is the touch voltage between the energized object and the feet of a person in contact with the

bject. It is equal to the difference in

voltage between the object and a point some distance away.

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How to limit step and touch potential

Providing low resistance path to ground Proper insulation between body and ground- By providing resistive surface layers Proper design and installation of earthing conductors Proper design and installation of earthing conductors Use of current limiting reactors Use of highly insulated shoes

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Typical Earthing Scheme for Construction Power Facilities

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Documentation

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Purpose/Importance of documentation

Adopt a systematic approach by following a robust safety systems during maintenance /operation. Leads towards zero accident . Minimises disruption in work Boost up confidence of the working professionals . Statutory Compliance – OHSAS 18001

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Documents

Release work permit routed through concerned departments Strictly adhere to the Lock Out Tag Out (LOTO) concept Raising and mitigation of NCR ( non-compliance report) on regular basis On line monitoring of NCR’s Compliance of Check list prior to installation and safe energisation .

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PERMIT TO WORK (PTW)

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To ensure safety

Lock out/Tag out - LOTO

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Maintenance & Testing

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Need for the Testing and Maintenance
Safety features to be adopted during Testing and

maintenance .

Contents-

maintenance .

Charging of power/Distribution transformer
Do’s and Don'ts in Testing & Maintenance ( T & M ) of

electrical equipment's

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Need for Testing and Periodic Manitenance

check the installation completeness.

check the healthiness of the individual equipment.

ensure the required integrated electrical power system.
ensure the protection system is in order to protect the

electrical equipment. electrical equipment.

verify proper functioning

verify that the performance of the installed equipment /systems meet with the specified design.

record performance data of the whole installation as the

baseline for future operation and maintenance.

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Safety features

Ensure the testing equipment and test kits are connected to Earthing system. Check that the testing power supply taken through proper fuse or RCCB. Ensure that the manufacturer catalogue, system Single Line Diagram available with Testing Engineer.

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Relay testing – Safety Features

Ensure the Earthing of relay casing and test kit Protection for Auxiliary supply and test kit power

confirm information about terminal connections of the following.
confirm information about terminal connections of the following.

Auxiliary supply Current terminal Potential terminal Out put contact

34 53667

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Charging of the Power/Distribution Transformer

Before “ Switch ON” or Charging of the following points to be checked- Visual Inspection. Oil Level in the Transformer Conservator tank. Bucholtz Relay Input / Out put Opened. Oil in Transformer Breather Pot.

Stopper installation of Transformer Wheel.

Transformer Tap position. Tightness of the Primary & Secondary Cable connection. Neutral Grounding Resistor kept “ON” Position. Setting of Oil Temperature Alarm & Trip. Setting of Winding Temperature Alarm & Trip.

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Charging of the Power/Distribution Transformers

Field Isolator Position “ON”. IR & PI and other routine test done of equipment along with Cable. Transformer Secondary side Breaker kept in “TEST” Position, for safety reason. If all checks found “OK or ACCEPTABLE” then transformer Primary side breaker can be closed. be closed. After Charging of the transformer A humming sound from transformer. Secondary side voltage check Transformer kept in ON-LOAD condition for a day and periodic noting of oil & winding temperature ..

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Testing & Maintenance

Understand the basics on the equipment's and the systems. Basics about the equipment to be tested, instruments and meters used for the testing and commissioning.

Do’s

Procedures to be adopted during testing and maintenance . Formats to be used testing and maintenance . Fair Ideas on test results, standards to be followed and reference value.

Purpose of testing, test results to compare.

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Don’t

Do not forget the safety norms. Do not start the testing of any equipment with out understanding and knowing the expected test results

Testing & Maintenance

the expected test results Do not switch on the equipment with out protection Do not leave the secondary terminal of CT under open condition. Do not leave the secondary terminal of PT in short circuit condition.

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