System Earthing or Grounding
Definition: In System earthing or grounding, the current carrying parts are directly connected to the ground. The grounding provides the return path for the leakage current and hence protects the power system equipment from damage.
When a fault occurs in the equipment, the current in all three phases of the equipment becomes unbalanced. The grounding discharges the fault current to the ground and hence makes the system balance.
Important Points:
- For grounding, black color wire is used.
- The System earthing or grounding balanced the unbalanced load.
- The grounding wire is placed between the neutral of the equipment and the earth.
- In grounding the equipment is not physically connected to the ground, and the current is not zero on the ground.
- The grounding gives the path to an unwanted current and hence protects the electrical equipment from damage.
- The grounding is classified into three types. They are the solid grounding, resistance grounding and reactance grounding.
Equipment Earthing
Definition:
The ‘earthing’ means the connection of the non-current carrying part of the equipment to the earth. When the fault occurs in the system, then the potential of the non-current part of the equipment raises, and when any human or stray animal touches the body of the equipment, then they may get shocked.
The earthing discharges the leakage current to the earth and hence avoids the personnel from the electric shock. It also protects the equipment from lightning strokes and provides the discharge path for the surge arrester, gap, and other devices.
Important Points:
- For earthing, green color wire is used.
- The earthing protects the equipment and human from an electrical shock.
- In earthing the earth electrode is placed between the equipment body and the earth pit which is placed under the ground.
- In earthing the system is physically connected to the ground and it is at zero potential.
- The earthing decreases the high potential of electrical equipment which is caused by a fault and thus protects the human body from the electrical shock.
- Earthing can be done in five ways. The different methods of earthing are pipe earthing, plate earthing, rod earthing, earthing through tap, and strip earthing.
The resistance of the earth wire should not be more than 1 ohm.