Most of the people often get confused to differentiate between these terms like earthing, grounding and bonding. Are you having difficulty to understand difference between Earthing, Grounding and Bonding? If yes, then, you are at right place to get rid of from this confusion for the rest of the your professional life.
Grounding is low impedance path for leakage current or voltage which travels through neutral wire to ground.
As we know that, In ideal case, Neutral should have zero current in a balanced three phase system.
In reality, that is not the case. It is almost impossible to have zero current in neutral as we have many single phase applications to run. This leakage current must be eliminated from the system to avoid any damage to the system. That is why we connect common point of all three phases in Star connected side of Transformer to ground and that point is called Neutral Point.
Earthing in mains electrical wiring system is a conductor that provides a low impedance path to the earth to prevent hazardous voltages from appearing on equipment.
Looks at below mentioned picture of unearthed system.
A transformer is connected and you can see live wire and neutral wire. Neutral point is connected to earth. These live wire and neutral wires are connected with electrical equipment having metal body. Due to damage of insulation or any reason, when live wire touches with metal body of equipment and develops charges on the metal surface. A person came to operate some fixture and he touches that body and the charges, developed on metal body, get the passage to pass through his body to ground and person receives shock. The intensity of shock depends on the amount of current passes through that body. The higher the amount of current and time, the severe intensity of the shock will be.
Now, just look at an earth protected system
The only difference from the above picture is connection of earth with metal body. This metal body is connected with earth system which is lowest resistance path for any fault current. Even in the condition of its contact with live wire, it does not give any shock to operator.
Why a Person will not get shock in this condition?
Because earthing system provides lowest resistance path for any fault current, which is lower than human internal body resistance so that is why current always follows lowest resistance path and it will directly go through ground instead of going through his body.
Bonding the connection of earth wire from one equipment to another equipment For example, if we have different machines in the factory and we have to connect all these machines to earthing system. All we need to do is to connect with main earth wire with one machine while loop it to other machines as well from this machine. That connection of earth from one machine to another machine is called bonding.