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7/23/2019 Earthing and Electrical Grounding Installation
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Earthing and Electrical Grounding Installation | A Complete Guide
What is Grounding or Earthing?
To connect the metallic (conductive) Parts of an Electric appliance or installations to theearth (ground) is called Earthing or GroundingIn other !ords" to connect the metallic parts of electric machiner# and devices to theearth plate or earth electrode (!hich is $uried in the moisture earth) through a thic%conductor !ire (!hich has ver# lo! resistance) for safet# purpose is %no!n as Earthingor groundingTo earth or earthing rather" means to connect the part of electrical apparatus such asmetallic covering of metals" earth terminal of soc%et ca$les" sta# !ires that do not carr#current to the earth Earthing can $e said as the connection of the neutral point of apo!er suppl# s#stem to the earth so as to avoid or minimi&e danger during discharge ofelectrical energ#
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Good to know
Difference between Earthing, Grounding and Bonding.
'et me clear the confusion among earhing" grounding and $onding
Earthingand Groundingis the same terms used for earthingGrounding is the
commonly wordused for earthing in the North Americanstandards li%e IEEE, NEC,
ANSIand ULetc !hile" Earthing is used in European" Common !ealth countries
and Britain standards like IS and IECetc
The !ord Bondingused for ointing t!o !ires (as !ell as conductors" pipes or
appliances together onding is %no!n as connecting the metallic parts of different
machines !hich is not considered to $e carr#ing electric current during normal operation
of the machines to $ring them at the same level of electric potential
Need of Earthing or Grounding. Why Earthing is Important?
The primar# purpose of earthing is to avoid or minimi&e the danger of electrocution" fire
due to earth lea%age of current through undesired path and to ensure that the potential
of a current carr#ing conductor does not rise !ith respect to the earth than its designed
insulation
When the metallic part of electrical appliances (parts that can conduct or allo! passage
of electric current) comes in contact !ith a live !ire" ma#$e due to failure of installations
or failure in ca$le insulation" the metal $ecome charged and static charge accumulates
on it I! a person touches such a charged metal " the result is a severe shoc%
To avoid such instances" the po!er suppl# s#stems and parts of appliances have to $e
earthed so as to transfer the charge directl# to the earth
Below are the basic needs of Earthing.
To protect human lives as !ell as provide safet# to electrical devices and appliances
from lea%age current
To %eep voltage as constant in the health# phase (If fault occurs on an# one phase)
To Protect Electric s#stem and $uildings form lighting
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To serve as a return conductor in electric traction s#stem and communication
To avoid the ris% of fire in electrical installation s#stems
Different Terms used in Electrical Earthing
Earth"The proper connection $et!een electrical installation s#stems via conductor to
the $uried plate in the earth is %no!n as Earth
Earthed"When an electrical device" appliance or !iring s#stem connected to the earth
through earth electrode" it is %no!n as earthed device or simple *Earthed+
Solidly Earthed" When an electric device" appliance or electrical installation is
connected to the earth electrode !ithout a fuse" circuit $rea%er or resistance,Impedance" It is
called *solidl# earthed+
Earth Electrode" When a conductor (or conductive plate) $uried in the earth for
electrical earthing s#stem It is %no!n to $e Earth Electrode Earth electrodes are in different
shapes li%e" conductive plate" conductive rod" metal !ater pipe or an# other conductor !ith
lo! resistance
Earthing Lead- The conductor !ire or conductive strip connected $et!een Earth
electrode and Electrical installation s#stem and devices in called Earthing lead
Earth Continuity Conductor" The conductor !ire" !hich is connected among different
electrical devices and appliances li%e" distri$ution $oard" different plugs and appliances etc in
other !ords" the !ire $et!een earthing lead and electrical device or appliance is called earth
continuit# conductor It ma# $e in the shape of metal pipe (full# or partial)" or ca$le metallic
sheath or fle.i$le !ire
Su# $ain Earthing Conductor- A !ire connected $et!een s!itch $oard and distri$ution
$oard ie that conductor is related to su$ main circuits
Earth %esistance" This is the total resistance $et!een earth electrode and earth in /
(0hms) Earth resistance is the alge$raic sum of the resistances of earth continuit# conductor"
earthing lead" earth electrode and earth
POINTS TO BE EARTHED
Earthing is not done an#ho! According to IE rules and IEE (Institute of Electrical
Engineers) regulations"
Earth pin of 12pin lighting plug soc%ets and 32pin po!er plug should $e efficientl# and
permanentl# earthed
All metal casing or metallic coverings containing or protecting an# electric suppl# line or
apparatus such as GI pipes and conduits enclosing 4I5 or P4C ca$les" iron clad s!itches"
iron clad distri$ution fuse $oards etc should $e earthed (connected to earth)
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The frame of ever# generator" stationar# motors and metallic parts of all transformers
used for controlling energ# should $e earthed $# t!o separate and #et distinct connections
!ith the earth
In a dc 12!ire s#stem" the middle conductors should $e earthed at the generating
station
6ta# !ires that are for overhead lines should $e connected to earth $# connecting at
least one strand to the earth !ires
Components of Earthing System
A complete electrical earthing s#stem consists on the follo!ing $asic components
Earth Continuity Conductor
Earthing Lead Earth Electrode
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Components of Electrical Earthing System
Earth Continuity Conductor or Earth Wire
That part of the earthing s#stem !hich interconnects the overall metallic parts ofelectrical installation eg conduit" ducts" $o.es" metallic shells of the s!itches"
distri$ution $oards"6!itches" fuses" 5egulating and controlling devices" metallic parts of
electrical machines such as" motors" generators" transformers and the metallic
frame!or% !here electrical devices and components are installed is %no!n as earth
!ire or earth continuit# conductor as sho!n in the a$ove fig
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The resistance of the earth continuit# conductor is ver# lo! According to IEEE rules"
resistance $et!een consumer earth terminal and earth Continuit# conductor (at the end)
should not $e increased than 7/ In simple !ords" resistance o! earth wire should #e
less than &'
6i&e of the Earth Continuit# Conductor or Earth Wire depends on the ca#le si(e used in
the wiring circuit
Size ofEarth Continuity Conductor
The cross sectional area of the Earth Continuity Conductor should not $e less than
the half of the cross sectional area of the thic%est !ire used in the electrical wiring
installation
Generall#" the si&e of the $are copper !ire used as earth continuit# conductor is 16WGut %eep in mind that" don8t use less than 736WG as earth !ire Copper strip is also
can $e used as earth continuit# conductor instead of $are copper !ire $ut don8t go for it
until manufacture recommend it
Earthing Lead or Earthing Joint
The conductor !ire connected $et!een earth continuit# conductor and earth electrode
or earth plate is called earthing oint or *Earthing lead+ The point !here earth continuit#
conductor and earth electrode meet is %no!n as *connecting point+ as sho!n in thea$ove fig
Earthing lead is the final part of the earthing s#stem !hich is connected to the earth
electrode (!hich is underground) through earth connecting point
There should $e minimum oints in earthing lead as !ell as lo!er in si&e and straight in
the direction
Generall#" copper !ire can $e used as earthing lead $ut" copper strip is also used for
high installation and it can handle the high fault current $ecause of !ider area than thecopper !ire
A hard dra!n $are copper !ire is also used as an earthing lead In this method" all earth
conductors connected to a common (one or more) connecting points and then" earthing
lead is used to connect earth electrode (earth plat) to the connecting point
http://www.electricaltechnology.org/2014/04/electrical-wire-cable-size-calculator.htmlhttp://www.electricaltechnology.org/2013/09/electrical-wiring.htmlhttp://www.electricaltechnology.org/2013/09/electrical-wiring.htmlhttp://www.electricaltechnology.org/2014/04/electrical-wire-cable-size-calculator.htmlhttp://www.electricaltechnology.org/2013/09/electrical-wiring.htmlhttp://www.electricaltechnology.org/2013/09/electrical-wiring.html7/23/2019 Earthing and Electrical Grounding Installation
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To increase the safet# factor of installation" t!o copper !ires are used as earthing lead
to connect the device metallic $od# to the earth electrode or earth plate Ie if !e use
t!o earth electrodes or earth plats" there !ould $e four earthing leads It should not $e
considered that the t!o earth leads are used as parallel paths to flo! the fault currents
$ut $oth paths should !or% properl# to carr# the fault current $ecause it is important for$etter safet#
Size of the Earthing Lead
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The si&e or area of earthing lead should not $e less than the half of the thic%est !ire
used in the installation
The largest si&e for earthing lead is 16WG and the minimum si&e should not $e less
than 96WG If 1:,;91 !ire is used or the load current is
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oth copper and iron can $e used as earthing electrode
The si&e of earth electrode (In case of copper)
6ta# tune
Good to know"
on8t use co%e (after $urning coal in the furnace to emit all the gases and other
components" the remaining 99D car$on is called co%e) or stone coal instead of charcoal
(!ood coal) $ecause it causes to corrosion in the earth plate
6ince" the !ater level is different in the different areas therefore" the depth for earth
electrode installation is also different in various areas ut" the depth for earth electrode
installation should not $e less than 7;ft (1 meter) and should $elo! 7 foot (1;39mm)
from the constant !ater level
$otors" Generator" +rans!ormersetc should $e connected from to earth electrode t!o
different places
Earth Plate or Earth Electrode Size for Small installation
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In small installation" use metallic rod (diameter B
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plate
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2). Pipe Earthing:
A galvani&ed steel and a perforated pipe of approved length and diameter is placed
verticall# in a !et soil in this %ind of s#stem of earthing It is the most common s#stem of
earthing
The si&e of pipe to use depends on the magnitude of current and the t#pe of soil The
dimension of the pipe is usuall# 3;mm (7Fin) in diameter and
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length of the pipe to $e $uried $ut usuall# it should $e 3:Fm (7FFft)
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3). Rod Earthing
it is the same method as pipe earthing A copper rod of 7
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If stranded conductor is used as earth !ire" then clean the end of the strands of the !ire
and ma%e sure it is in the straight and parallel position !hich is possi$le then to connect
tightl# to the !aterman pipe
5). Strip or Wire Earthing:
In this method of earthing" strip electrodes of cross2section not less than
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Earth continuit# conductor !hich is connected to the $od# and metallic parts of all
installation should $e tightl# connected to earth lead
7; At last ($ut not least)" test the overall earthing s#stem through earth tester If ever#thing
is going a$out the planning" then fill the pit !ith soil The ma.imum allo!a$le resistance for
earthing is 7/ If it is more than 7 ohm" then increase the si&e (not length) of earth lead andearth continuit# conductors Leep the e.ternal ends of the pipes open and put the !ater time
to time to maintain the moisture condition around the earth electrode !hich is important for
the $etter earthing s#stem
SI specification for Earthing
4arious specifications in respect to earthing as recommended $# Indian 6tandards are
given $elo! Mere are fe!
An earthing electrode should not $e situated (installed) close to the $uilding !hose
installation s#stem is $eing earthed at least more than 7Fm a!a#
The earth resistance should $e lo! enough to cause the flo! of current sufficient to
operate the protective rela#s or $lo! fuses It8s value is not constant as it varies !ith !eather
$ecause it depends on moisture ($ut should not $e less than 7 0hm)
The earth !ire and earth electrode !ill $e the same material
The earthing electrode should al!a#s $e placed in a vertical position inside the earth or
pit so that it ma# $e in contact !ith all the different earth la#ers
Dangers Of Not Earthing A Supply System
As emphasi&ed on earlier" earthing is provided in order
To avoid electric shoc%
To avoid ris% of fire as a result of earth lea%age current through un!anted path and
To ensure that no current carr#ing conductor rises to a potential !ith respect to general
mass of earth than its designed insulation
Mo!ever" if e.cessive current is not earthed" appliances !ill $e damaged !ithout the
help of fuse in place Nou should note that e.cessive current are earthed at their
generating stations !hich is !h# earth !ires carries ver# little or no current at all It
therefore implies that it is not necessar# to earth an# of the !ires (live" earth and neutral
!ires) contained in a P4C Earthing the live !ire is catastrophic
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I have seen a person %illed simpl# $ecause a live !ire got cut from overhead pole and
fell to the ground !hile the ground !as !et E.cessive current is earthed at generating
stations and if at all the earthing is not efficient due to fault" earth fault interrupters !ill
$e there to help use help onl# !hen the po!er transmitted is a$ove the rating of our
appliances" it $loc%s the current from reaching our appliances $# $lo!ing off andprotecting our appliances in the process
In our electrical appliances" if e.cessive currents are not earthed" !e !ould e.perience
severe shoc% Earthing ta%es place in electrical appliances onl# !hen there is a pro$lem
and it is to save us from danger If in an electronic installation" a metallic part of an
electrical appliance comes in direct contact !ith a live !ire that results from ma#$e
failure of installation or other!ise" the metal !ill $e charged and static charge !ill
accumulate on it
If #ou happen to touch the metallic part at that moment #ou !ill $e &apped ut if themetallic part of the appliance is earthed" the charge !ill $e transferred to earth instead
of accumulating on the metallic part of the appliance Current don8t flo! through earth
!ires in electrical appliances" it does so onl# !hen there is pro$lem and onl# to direct
the un!anted current to earth in order to protect us from severe shoc%
In addition" if a live !ire touches accidentall# (in a fault# s#stem) to the metallic part of a
machine =o!" if a man touches that metallic part of the machine" then the current !ill
flo! through their $od# to the ground" hence" he !ill get shoc%ed (electrocuted) !hich
ma# lead to serious inuries even to death That8s !h# earthing is so important?
Electrical Grounding & Earthing.. To be continued
Please su$scri$e $elo!" if #ou !ant to get the upcoming post
a$out EarthingGroundingsuch as-
Calculate the si&e of Earth Continuit# Conductor" Earthing 'ead O Earth Electrodes for
differnt electrical devices and eHuipment such motors" transformers" home !iring etc $#
6imple calculations
Earthing Circuit and Earth ault Current
Protection of Earthing 6#stem and Additional devices used in the Earthing , Grounding
6#stem
Points To remem$er !hile Providing Grounding , Earthing
Important Instruction for Proper earthing s#stem
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Electricit# rules a$out Earthing
Mo! to Test Earth 5esistance $# Earth Tester
Mo! to test Earth loop 5esistance $# Am2Jeter O 4oltmeter
Protective Jultiple Earthing
And much more>