CONTENTS
1.0 INTRODUCTION 01
1.1 ADVANTAGES OF EARTHING 02
1.2 TERMINOLOGY 03
1.3 EARTH AS CONDUCTOR 05
1.4 IMPORTANT INDIAN ELECTRICITY
RULE RELATED TO EARTHING 05
1.5 GENERAL REQUIREMENT
FOR EARTHING 07
1.6 DIFFERENCE BETWEEN
GROUNDING AND EARTHING 10
1.7 HUMAN ELEMENT & ELECTRIC
SHOCK 11
1.8 FACTORS WHICH DETERMINE
RESISTIVITY OF SOIL 13
1.9 LOCATION OF EARTH ELECTRODE 19
2.0 DESIGN, SIZE AND TYPES OF EARTH
ELECTRODE 20
2.1 ELECTRODE RESISTANCE TO EARTH 20
2.2 INFLUENCING FACTORS FOR
ELECTRODE RESISTANCE 21
2.3 ELECTRODE SIZE 22
2.4 DESIGN OF EARTH ELECTRODES 22
2.5 EARTH ELECTRODE
2.6 TYPES OF ELECTRODES 26
2.7 TYPES OF EARTHING 32
2.8 EARTHING LEAD 35
3.0 EARTHING SYSTEM 35
3.1 CLASSIFICATION OF EARTHING 35
3.2 EARTHING SYSTEM IN SUB STATION 41
3.3 EARTHING OF VARIOUS EQUIPMENT IN
THE SUB-STATIONS 43
3.4 DISTRIBUTION TRANSFORMER
STRUCTURE EATHING 47
3.5 EARTHING OF DISTRIBUTION LIENE
STRUCTURES 51
3.6 EARTHING AT CONSUMER’S PREMISES 53
3.7 EARTHING IN INDUSTRIAL PREMISES 56
3.8 DANGERS OF IMPERFECT EARTHING 57
3.9 PRECAUTIONS 58
4.0 TESTING & MAINTENANCE 59
4.1 TESTING OF EARTHING SYSTEM 59
4.2 MAINTENANCE SCHEDULES 62
5.0 MAINTENANCE FREE EARTHING 65
5.1 EARTH RESISTANCE 66
5.2 APPLICATIONS 66
5.3 MAINTENANCE FREE EARTHING SYSTEM 66
6.0 DO’S & DON’TS 77
6.1 DO’S 77
6.2 DON’T 78
REFRENCES
INTRODUCTION
Earthing is a connection done through a metal
link between the body of any electrical appliance, or neutral point, as the case may be, to the deeper ground
through these metal links, normally of MS flat, CI flat,GI wire penetrated to the earth grid. Object of earthing is that all parts of apparatus other than live parts shall be at earth potential.
Earthing eliminates the possibility of any
dangerous potential rise on the body of electrical equipment. It drains away the charge on the equipment through an earth connection. When an earth fault is
occurres such as winding insulation failure etc. causes a heavy current flow into the general mass of the earth.
This causes blowing out of fuse or operation/ tripping of protective devices. The potential under and around of the object shall be uniform nearly to zero w.r.t. earth.
Apart from this it is to ensure that operators or working personnel shall be at earth potential at all times, so that there will be no potential difference to cause shock or injury to a person, whenever any short
circuit takes place.
The primary requirements of a good earthing
system are:
a. It stabilizes circuit potential with respect to
ground potential and limits the potential rise.
b.It protects men & materials from injury or
damage due to over voltage or touching.
c. It provides low impedance path to fault currents to ensure prompt & consistent operation of protective devices during earth fault.
d. It keeps the maximum voltage gradient along the surface inside & around the substation within safe limits during earth fault.
e. It protects underground cables from overall
ground potential rise & voltage gradient during
ground fault in the system
ADVANTAGES OF EARTHING
For efficient/effective operation of any power
system, it is essential to connect the neutral to suitable
earth connection. The following are the few advantages:
• Reduced operation & maintenance cost
• Reduction in magnitude of transient over voltages.
• Improved lightning protection.
• Simplification of ground fault location.
• Improved system and equipment fault protection.
• Improved service reliability
• Greater safety for personnel & equipment
• Prompt and consistent operation of protective devices during earth fault
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