Earthing in Electrical
Description:
Electrical earthing is a system in which electricity is discharged directly to earth through low resistance path or earth conductor. Earth has very special place and benefit in electrical system. Earthing is a must for industrial electrical installations. In earthing the non electricity carrying conducting parts like metal body of electrical machines like motor and transformer as well as the neutral is connected with the help of conducting wire to the grounder electrode. The resistance of the earthing system is kept as low as possible. 0 Ohm to 3 Ohm is a typical value for earthing system.
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| Electrical system without earthing |
In older days when metals were not expensive, earthing plate and conduction used were made of copper and brass. But as today metals become precious, galvanized iron plate and conductor is used for earthing. The purpose of earthing is to provide an easy and simple way to leakage currents. In case of short circuit the current of the equipment passes though the earth which has very low resistance closed to 0 Ohm. So in this way the system and human is protected from damage.
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| Electrical system with earthing or grounding |
Electrical Earthing types
Any electrical system or equipment have two main non current carrying part. First is the neutral of the system and the second one is the metal frame of the electrical equipment like motor body, transformer body, panel etc. Earthing of these two parts is a must. Due to these two parts of system, earthing is categorized into two kinds or types.
- Equipment earthing
- Neutral earthing
- Equipment earthing
In this type or kind of earthing the metal frame or body of the electrical equipment is connected to the ground or earthing system with the help of earthing or grounding conductor. As the body of the electrical equipment is isolated from the electrical system or there is thick insulation provided between the current path and body of the equipment, normally no current flows through the body of equipment. If any faults occur inside the equipment and insulation breakdown occurs between the current carrying parts of the equipment and the metallic body of the equipment, the earth is providing an easy and low resistance path to the current and no damage occurs to humans touching the metal frame of the equipment or to the equipment itself. In some cases if the short circuit is occur very close to the phase, the supply fuse will blow or the circuit breaker would trip, hence the equipment will be isolated from the electrical supply system or means. In this way the electrical equipment as well as the human will be protected from loss.
- Neutral Earthing
The neutral of the supply system is connected directly to the grounded or earth electrode. The other name for the neutral earthing or grounding is the system earthing or system grounding. The star point of the electrical system of equipment is known as neutral. So the star point or neutral is connected to ground or earth with the help of grounding or earthing conductor. This kind of earthing is normally provided to motors, transformers and generators where there is star winding in the machine.
Need and Importance of Earthing
Earthing of the electrical equipment is a must due to the following
- Earthing gives a low resistance path to the leakage current at the time of fault and insulation breakdown between power system and the metal body or frame.
- Earthing protects humans from electric shock if live electrical conductors touch to the metal parts of electrical equipment.
- Earthing prevents equipment and human from surges and high voltage discharges.
Grounding or earthing is done by connecting the respective parts electrically in electrical installation to the electrode which is buried under the ground level having very low resistance. The buried electrode have a pipe connection through which water can be filled in to reduce the earthing or grounding resistance.
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| Earthing electrode |
When fault come in electrical system, fault leakage current flows from the equipment to the earthing system through the earth conductor and in this way the earthing system protects the equipment from the fault current. At the time of the fault, The leakage current flows through the earth. The voltage or potential difference at equipment metal frame is equal to quantity of current multiplied to the earth resistance.
Earthing is compulsory for any electrical system. Electrical company has condition for supplying power to any installation that they must have good working low resistance earthing system. The electrical supply have right to discontinue the supply if the installation have bad earthing or high resistance earthing.
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