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Grounding is a process which is generally used in three phase systems for connecting the neutral of the system to ground. This is done in order to avoid arcing faults which happen when LG fault occurs in a system with ungrounded neutral. In that case the phase voltage magnitude becomes equal to line voltage which can cause Insulator Flashover or Puncture in Insulator.
Hence, neutral must be grounded to avoid such a situation and there are various techniques used such as Reactance grounding, Resistance grounding, Peterson coil etc.
Earthing is a process in which outer body of the device is connected to ground so as to provide a path to ground for the surface charge. This is done for the safety of operator so that he does not get a shock while using the device.
So, we can say that both techniques involve connection to ground but their purpose is entirely different.
- Earthing means connecting the dead part (it means the part which does not carries current under normal condition) to the earth for example electrical equipment’s frames, enclosures, supports etc.
- The purpose of earthing is to minimize risk of receiving an electric shock if touching metal parts when a fault is present. Generally green wire is used for this as a nomenclature.
- Under fault conditions the non-current carrying metal parts of an electrical installation such as frames, enclosures, supports, fencing etc. may attain high potential with respect to ground so that any person or stray animal touching these or approaching these will be subjected to potential difference which may result in the flow of a current through the body of the person or the animal of such a value as may prove fatal.
- 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.
- Grounding means connecting the live part (it means the part which carries current under normal condition) to the earth for example neutral of power transformer.
- Grounding is done for the protections of power system equipment and to provide an effective return path from the machine to the power source. For example grounding of neutral point of a star connected transformer.
- Grounding refers the current carrying part of the system such as neutral (of the transformer or generator).
- Because of lightning, line surges or unintentional contact with other high voltage lines, dangerously high voltages can develop in the electrical distribution system wires. Grounding provides a safe, alternate path around the electrical system of your house thus minimizing damage from such occurrences.
- Generally Black wire is used for this as a nomenclature.
- All electrical/electronic circuits (AC & DC) need a reference potential (zero volts) which is called ground in order to make possible the current flow from generator to load. Ground is May or May not be earthed. In Electrical Power distribution it is either earthed at distribution Point or at Consumer end but it is not earthed in Automobile( for instance all vehicles’ electrical circuits have ground connected to the chassis and metallic body that are insulated from earth through tires). There may exist a neutral to ground voltage due to voltage drop in the wiring, thus neutral does not necessarily have to be at ground potential.
- 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 transformer’s secondary winding.
Micro Difference between earthing & Grounding
- There is no major difference between earthing and Grounding, both means “Connecting an electrical circuit or device to the Earth”. This serves various purposes like to drain away unwanted currents, to provide a reference voltage for circuits needing one, to lead lightning away from delicate equipment. Even though there is a micro difference between grounding & earthing.
(1) Difference in Terminology:
- In USA term Grounding is used but in UK term Earthing is used.
(2) Balancing the Load Vs Safety:
- Ground is a source for unwanted currents and also as a return path for main current some times. While earthing is done not for return path but only for protection of delicate equipments. It is an alternate low resistance path for current.
- When we take out the neutral for a three phase unbalanced connection and send it to ground, it is called grounding. Grounding is done to balance unbalanced load. While earthing is used between the equipment and earth pit so as to avoid electrical shock and equipment damage.
(3) Equipment Protection Vs Human Safety:
- Earthing is to protect the circuit elements whenever high voltage is passed by thunders or by any other sources while Grounding is the common point in the circuit to maintain the voltage levels.
- 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.
- Earthing is a preventive measure while Grounding is just a return path
- The ground conductor provides a return path for fault current when a phase conductor accidentally comes in contact with a grounded object. This is a safety feature of the wiring system and we would never expect to see grounding conductor current flow during normal operation.
- Do not Ground the Neutral Second time When It is grounded either at Distribution Transformer or at Main service Panel of Consumer end.
- Grounding act as neutral. But neutral cannot act as ground.
(4) System Zero Potential Vs Circuit Zero Potential:
- Earthing and Grounding both is refer to zero potential but the system connected to zero potential is differ than Equipment connected to zero potential .If a neutral point of a generator or transformer is connected to zero potential then it is known as grounding. At the same time if the body of the transformer or generator is connected to zero potential then it is known as earthing.
- The term “Earthing means that the circuit is physically connected to the ground and it is Zero Volt Potential to the Ground (Earth) but in case of “Grounding” the circuit is not physically connected to ground, but its potential is zero(where the currents are algebraically zero) with respect to other point, which is also known as “Virtual Grounding.”
- Earth having zero potential whereas neutral may have some potential. That means neutral does not always have zero potential with respect to ground. In earthing we have Zero Volt potential references to the earth while in grounding we have local Zero Volt potential reference to circuit. When we connect two different Power circuits in power distribution system, we want to have the same Zero Volt reference so we connect them and grounds together. This common reference might be different from the earth potential.