INTRODUCTION
Earthing is an integral part of any electrical installation.
SOME FUNDAMENTALS
Earth : From an electrical engineering point of view Earth is defined as the conductive mass of the earth, where electric potential at any point is
conventionally taken as zero. Being electrically neutral and at zero potential, the earth provides a common reference for voltage measurements.
Earthing : An electric connection to the general mass of earth, where dimensions are very large in comparison to the electrical system being considered.
The terms ‘Ground’ and ‘Grounding’ are synonymous with ‘Earth’ and ‘Earthing’ and are more prevalent in some countries like North America.
Equipotential Bonding : Electrical connection putting various exposed conductive parts and extraneous conductive parts at an equal potential.
Exposed Conductive Part : A conductive part of an equipment that can be touched and is not a live part but that may become live under fault conditions.
Extraneous Conductive Part : A conductive part liable to transmit a potential including earth potential and not forming part of the electrical installation.
NEED FOR EARTHING
Earthing is of utmost importance for safety of plant, equipment, property and personnel as well as animal life. In the absence of a well designed effective earthing system, earth fault conditions may lead to tremendous loss of property and life.
The main objectives of earthing are as follows :
- To ensure safety of personnel and property from hazards of electric shock and electric fires.
- To ensure that system voltages on healthy lines remain within reasonable limits under fault conditions thereby preventing insulation breakdowns.
- To provide a low impedance path to facilitate the satisfactory operation of protective devices under fault conditions.
- To minimize arcing burn downs, as in an earthed system, an arcing fault would produce a current in the ground path thereby providing an easy
means of detecting and tripping against phase to earth arcing fault breakdowns.
- To provide an equipotential platform on which electronic equipment can operate.
- To provide an alternative path for induced current and minimize the electrical noise in cables.
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