Earthing
To connect the
metallic (conductive) Parts of an Electric appliance or installations to the
earth (ground) is called Earthing
or Grounding.
In other words, to
connect the metallic parts of electric machinery and devices to the earth plate
or earth electrode (which is buried in the moisture earth) through a thick
conductor wire (which has very low resistance) for safety purpose is known as Earthing or grounding.
To earth or earthing
rather, means to connect the part of electrical apparatus such as metallic
covering of metals, earth terminal of socket cables, stay wires that do not
carry current to the earth. Earthing can be said as the connection of the
neutral point of a power supply system to the earth so as to avoid or minimize
danger during discharge of electrical energy.
Need of Earthing or Grounding. Why Earthing is Important?
The primary purpose
of earthing is to avoid or minimize the danger of electrocution, fire due to
earth leakage of current through undesired path and to ensure that the
potential of a current carrying conductor does not rise with respect to the
earth than its designed insulation.
When the metallic
part of electrical appliances (parts that can conduct or allow passage of
electric current) comes in contact with a live wire, maybe due to failure of
installations or failure in cable
insulation,
the metal become charged and static charge accumulates on it. If a person touches such a charged
metal, the result is a severe shock.
To avoid such
instances, the power supply systems and parts of appliances have to be earthed
so as to transfer the charge directly to the earth.
Below are the basic
needs of Earthing.
- To protect human lives as well as
provide safety to electrical devices and appliances from leakage current.
- To keep voltage as constant in
the healthy phase (If fault occurs on any one phase).
- To Protect Electric system and
buildings form lighting.
- To serve as a return conductor in
electric traction system and communication.
- To avoid the risk of fire in
electrical installation systems.
Importance of Earthing:
Earthing or grounding is done for
safety of equipment and human beings (including all animals and plants).
Equipment Safety:
The outer housing of an electrical equipment is earthed by directly connecting it to a earth grid or earth electrode, thereby providing a low resistance path to ground. In case of a fault involving earth the live part of the equipment gets connected with the low resistance earth path. This produces high earth fault current and the protective devices in the circuit disconnects the circuit from the power source thereby reducing further damage to the equipment.
Neutral of electrical equipment are also earthed for equipment safety. Like, neutral of generators in power plants are earthed through Neutral Grounding Resistor to limit the earth fault current. Three phase transformer's neutral are earthed to provide neutral point to supply single phase loads like lighting and small appliances.
Human Safety:
If a person touches an appliance which has an earth fault in it he will not get an electric shock as his body (standing on the earth) and the equipment's body are at the same potential provided the equipment is earthed properly. Thus proper earthing protects a person from getting electric shock.
Equipment Safety:
The outer housing of an electrical equipment is earthed by directly connecting it to a earth grid or earth electrode, thereby providing a low resistance path to ground. In case of a fault involving earth the live part of the equipment gets connected with the low resistance earth path. This produces high earth fault current and the protective devices in the circuit disconnects the circuit from the power source thereby reducing further damage to the equipment.
Neutral of electrical equipment are also earthed for equipment safety. Like, neutral of generators in power plants are earthed through Neutral Grounding Resistor to limit the earth fault current. Three phase transformer's neutral are earthed to provide neutral point to supply single phase loads like lighting and small appliances.
Human Safety:
If a person touches an appliance which has an earth fault in it he will not get an electric shock as his body (standing on the earth) and the equipment's body are at the same potential provided the equipment is earthed properly. Thus proper earthing protects a person from getting electric shock.
Circuit symbols are used in circuit diagrams which show how a circuit is connected together. The actual layout of the components is usually quite different from the circuit diagram. To build a circuit you need a different diagram showing the layout of the parts on stripboard or printed circuit board.
