JOB ROLE Consumer Energy Meter Technician


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JOB ROLE – Consumer Energy Meter Technician
Sector: Power (Qualification Pack Code : PSS/Q0107)
PSS Central Institute of Vocational Education Shyamla Hills, Bhopal – 462013, Madhya Pradesh, India
____________________________________________________
www.psscive.ac.in
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Unit 1: Basic Electricity -1 Session 4: Importance of Earthing System
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Content
Title Session Objective Introduction Earthing Specification for earthing Types of Earthing Description of Various Earthing

Slide No. 4 5 6-7
8-10 11-15 16-15
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Session Objectives
1. The student will be able to understand the need of earthling for electrical apparatus.
2. Know the procedure for installation of proper earthling. 3. Ensure safety of human life and his property from electric
shock and fires. 4. Know how Earthing System works
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Introduction
The proper metallic connection between electrical machines and devices with the earth plate commonly known as earth electrode through a thick wire of low resistance to provide safety is known as Earthing. Earthing System in Electrical circuit is for safety purpose. The Main objective of earthing system is to provide an alternative path for high and dangerous current to flow in the general mass of earth so that the problem of electric shock and damaging of equipment will be protected. Metallic part of an equipment are earthed and if the equipment’s insulation fails than there will be no dangerous current present on the surface of the equipment. The circuit gets sorted and fuse will blow immediately due to low resistance of earth.
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Earthing
• Earthing means connection of non-current caring parts (metallic parts) of electrical apparatus to the general mass of earth to discharge of electrical energy takes place without any danger.
• Earthing is done by connecting the appliance or machinery to earth by good conductor known as earth electrode. Earthling is done to save human life from the danger of electrical shock, in case human body will come in contact of live wire of electricity.
• If earthing has done in proper manner and the metallic part come in the connect of live wire, the discharge takes places to the earth. In this condition due to low resistance of earth a large current flows to the earth. If the flowing current is exceed the limiting value of fuse blow off or MCB will trip and cut off the appliances from supply.
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• Different Terms used in Electrical Earthing
• Earth: The proper electrical connection between electrical installation and general mass of earth is known as Earth.
• Earthed: When an electrical machine, appliance or wiring connected to the earth through earth electrode, it is known as Earthed.
• Earth Electrode: When a pipe or plate buried in the earth for discharge of electricity is known as Earth Electrode.
• Earthing Lead: The conducting wire or conductive strip connected between Earth electrode and Electrical installation and machine is called Earthing lead.
• Earth Resistance: This is the resistance between earth electrode and earth in Ohms.
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Specification for earthing

• Distance of earth from building --

More than 1.5 meter from the building.

• Size of Earth Electrode

-- Not be less then 2.9mm² or 14 SWG

• Resistance of Earth

-- not greater than 8 ohm.

• The earth electrode and earth wire will be same material.

8 © PSS Central Institute of Vocational Education, Bhopal 2019

• Points to be earth: • Earth pin of 3 pin and 5 pin plug and socket. • All metal part of electrical machine e.g. motor, heater geyser, and
mixer. • Metallic frame of electrical machines. • The neutral conductor of 3phase 4wire system. • Pole, tower, armoring of cable. • Stay wire of overhead lines.
9 © PSS Central Institute of Vocational Education, Bhopal 2019

Importance of electrical earthing: To save human life from the danger of shock from leakage current. To maintain the line voltage constant. To protect large machine and building from atmosphere lighting. To avoid the risk of accident in electrical substation and other installation.

Earth Resistance of different Electrical Installation:

Large Power Station

--

0.5 Ohm.

Major Power Station

--

1.0 Ohm

Small Sub-Station

-- 2.0 Ohm

In House wiring and such other case - 5.0 to 8.0 Ohm

© PSS Central Institute of Vocational Education, Bhopal 2019 10

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JOB ROLE Consumer Energy Meter Technician