earthing, grounding and bonding

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  • 10/16/2013

    1

    EARTHING, EARTHING, EARTHING, EARTHING,

    GROUNDING GROUNDING GROUNDING GROUNDING

    AND AND AND AND

    BONDINGBONDINGBONDINGBONDING

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    Introduction:

    One of the most misunderstood and confused

    concept is difference between Bonding,

    Grounding and Earthing. Bonding is more

    clear word compare to Grounding and

    Earthing but there is a micro difference

    between Grounding and Earhing.

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    Ground or earth in a mains electrical wiringsystem is a conductor that provides a lowimpedance path to the earth to preventhazardous voltages from appearing onequipment.

    The Earthing is to reference our electrical sourceto earth (usually via connection to some kind ofrod driven into the earth or some other metalthat has direct contact with the earth).

    The grounded circuits of machines need to havean effective return path from the machines to thepower source in order to function properly (Hereby Neutral Circuit).

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    EARTHING Earthing means connecting the dead part (it means the

    part which does not carries current under normalcondition) to the earth for example electricalequipments frames, enclosures, supports etc.

    The purpose of earthing is to minimize risk of receivingan electric shock if touching metal parts when a fault ispresent. Generally green wire is used for this as anomenclature.

    Under fault conditions the non-current carrying metalparts of an electrical installation such as frames,enclosures, supports, fencing etc. may attain highpotential with respect to ground so that any person orstray animal touching these or approaching these willbe subjected to potential difference which may resultin the flow of a current through the body of the personor the animal of such a value as may prove fatal.

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    To avoid this non-current carrying metal parts of

    the electrical system are connected to the general

    mass of earth by means of an earthing system

    comprising of earth conductors to conduct the

    fault currents safely to the ground.

    Earthing has been accomplished through bonding

    of a metallic system to earth. It is normally

    achieved by inserting ground rods or other

    electrodes deep inside earth.

    Earthing is to ensure safety or Protection of

    electrical equipment and Human by discharging

    the electrical energy to the earth.

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    Equipment Protection Vs Human Safety:

    Earthing is to protect the circuit elements whenever high voltage ispassed by thunders or by any other sources while Grounding is thecommon point in the circuit to maintain the voltage levels.

    Earth is used for the safety of the human body in fault conditionswhile Grounding (As neutral earth) is used for the protection ofequipments.

    Earthing is a preventive measure while Grounding is just a returnpath

    The ground conductor provides a return path for fault current whena phase conductor accidentally comes in contact with a groundedobject. This is a safety feature of the wiring system and we wouldnever expect to see grounding conductor current flow duringnormal operation.

    Do not Ground the Neutral Second time When It is groundedeither at Distribution Transformer or at Main service Panel ofConsumer end.

    Grounding act as neutral. But neutral cannot act as ground.

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    GROUNDING Grounding means connecting the live part (it means the

    part which carries current under normal condition) to theearth for example neutral of power transformer.

    Grounding is done for the protections of power systemequipment and to provide an effective return path from themachine to the power source. For example grounding ofneutral point of a star connected transformer.

    Grounding refers the current carrying part of the systemsuch as neutral (of the transformer or generator).

    Because of lightening, line surges or unintentional contactwith other high voltage lines, dangerously high voltages candevelop in the electrical distribution system wires.Grounding provides a safe, alternate path around theelectrical system of your house thus minimizing damagefrom such occurrences.

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    Generally Black wire is used for this as a nomenclature.

    All electrical/electronic circuits (AC & DC) need areference potential (zero volts) which is called groundin order to make possible the current flow fromgenerator to load. Ground is May or May not beearthed. In Electrical Power distribution it is eitherearthed at distribution Point or at Consumer end but itis not earthed in Automobile( for instance all vehicleselectrical circuits have ground connected to the chassisand metallic body that are insulated from earththrough tires). There may exist a neutral to groundvoltage due to voltage drop in the wiring, thus neutraldoes not necessarily have to be at ground potential.

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    In a properly balanced system, the phase

    currents balance each other, so that the total

    neutral current is also zero. For individual

    systems, this is not completely possible, but

    we strive to come close in aggregate. This

    balancing allows maximum efficiency of the

    distribution transformers secondary winding

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    Balancing the Load Vs Safety:

    Ground is a source for unwanted currents andalso as a return path for main current sometimes. While earthing is done not for return pathbut only for protection of delicate equipments. Itis an alternate low resistance path for current.

    When we take out the neutral for a three phaseunbalanced connection and send it to ground, itis called grounding. Grounding is done to balanceunbalanced load. While earthing is used betweenthe equipment and earth pit so as to avoidelectrical shock and equipment damage.

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    Micro Difference between earthing & Grounding:

    There is no major difference between earthingand Grounding, both means Connecting anelectrical circuit or device to the Earth. Thisserves various purposes like to drain awayunwanted currents, to provide a referencevoltage for circuits needing one, to leadlightning away from delicate equipment. Eventhough there is a micro difference betweengrounding & earthing.

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    System Zero Potential Vs Circuit Zero Potential:

    Earthing and Grounding both is refer to zeropotential but the system connected to zero potential isdiffer than Equipment connected to zero potential .If aneutral point of a generator or transformer isconnected to zero potential then it is knownas grounding. At the same time if the body of thetransformer or generator is connected to zero potentialthen it is known as earthing.

    The term Earthing means that the circuit is physicallyconnected to the ground and it is Zero Volt Potential tothe Ground (Earth) but in case of Grounding thecircuit is not physically connected to ground, but itspotential is zero(where the currents are algebraicallyzero) with respect to other point, which is also knownas Virtual Grounding.

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    Conclusion:

    Ground is a source for unwanted currents and

    also as a return path for main current. While

    earthing is done not for return path but only

    for protection of delicate equipments. It is an

    alternate low resistance path for current.

    Earth is used for the safety of the human body

    in fault conditions while Grounding (As neutral

    earth) is used for the protection of

    equipments.

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    BONDING

    Bonding is simply the act of joining two electricalconductors together. These may be two wires, a wireand a pipe, or these may be two Equipments.

    Bonding has to be done by connecting of all the metalparts that are not supposed to be carrying currentduring normal operations to bringing them to the sameelectrical potential.

    Bonding ensures that these two things which arebonded will be at the same electrical potential. Thatmeans we would not get electricity building up in oneequipment or between two different equipment. Nocurrent flow can take place between two bondedbodies because they have the same potential.

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    Bonding, itself, does not protect anything. However, if oneof those boxes is earthed there c