What is the difference between Bonding, Grounding and Earthing?

Introduction

One of the most misunderstood and confused concept is difference between Bonding, Grounding and Earthing. Bonding is more clear word compare to Grounding and Earthing, but there is a micro difference between Grounding and Earhing.

Earthing and Grounding are actually different terms for expressing the same concept.

 

Ground or earth in a mains electrical wiring system is a conductor that provides a low impedance path to the earth to prevent hazardous voltages from appearing on equipment. Earthing is more commonly used in Britain, European and most of the commonwealth countries standards (IEC, IS), while Grounding is the word used in North American standards (NEC, IEEE, ANSI, UL).

The earthing connection to switchboard rear door (metal parts)

We understand that Earthing and Grounding are necessary and have an idea how to do it but we don’t have crystal clear concept for that. We need to understand that there are really two separate things we are doing for same purpose that we call Grounding or Earthing. The Earthing is to reference our electrical source to earth (usually via connection to some kind of rod driven into the earth or some other metal that has direct contact with the earth).

The grounded circuits of machines need to have an effective return path from the machines to the power source in order to function properly (Here by Neutral Circuit).
In addition, non-current-carrying metallic components in a System, such as equipment cabinets, enclosures, and structural steel, need to be electrically interconnected and earthed properly so voltage potential cannot exist between them. However, troubles can arise when terms like “bonding”, “grounding”, and “earthing” are interchanged or confused in certain situations.

In TN Type Power Distribution System, in US NEC (and possibly other) usage: Equipment is earthed to pass fault Current and to trip the protective device without electrifying the device enclosure. Neutral is the current return path for phase. These Earthing conductor and Neutral conductor are connected together and earthed at the distribution panel and also at the street, but the intent is that no current flow on earthed ground, except during momentary fault conditions.

 Here we may say that Earthing and grounding are nearly same by practice.
But In the TT Type Power Distribution System (in India) Neutral is only earthed (here it is actually called Grounding) at distribution source (at distribution transformer) and Four wires (Neutral and Three Phase) are distributed to consumer. While at consumer side all electrical equipment body are connected and earthed at consumer premises (here it is called Earthing).
Consumer has no any permission to mix Neutral with earth at his premises here earthing and grounding is the different by practice.

In both above case Earthing and Grounding are used for the same Purpose. Let’s try to understand this terminology one by one....Click here for full article