Earthing System

Definition - What does Earthing System mean?

In electricity supply systems, an earthing system defines the electrical potential of the conductors relative to that of the Earth's conductive surface. The choice of earthing system has implications for the safety and electromagnetic compatibility of the power supply.

The function of an earthing system is to provide:

  • Protective earthing
  • Functional earthing
  • Lightning protection

Regulations for earthing systems vary considerably among countries and among different parts of electric systems. Most low-voltage systems connect one supply conductor to the earth (ground).

An earthing system is also known as protective earth or a grounding system.

Corrosionpedia explains Earthing System

An earthing system is circuitry which connects parts of the electric circuit with the ground. It affects the magnitude and distribution of short circuit currents through the system, and the effects it creates on equipment and people in the proximity of the circuit. An earthing system avoids this hazard by keeping the exposed conductive surfaces of a device at earth potential.

A functional earth connection serves a purpose other than providing protection against electrical shock. A functional earth connection may carry a current during the normal operation of a device. Functional earth connections may be required by devices such as surge suppression and electromagnetic-compatibility filters, some types of antennas and various measurement instruments.

Earthing systems should be constructed in such a manner and of such materials, that they perform correctly over the whole expected lifespan, at a reasonable construction cost. The required properties are:

  • Low earthing resistance and favorable earth surface potential distribution
  • Adequate current carrying capacity
  • Long durability

The durability of an earthing system depends mainly on its capability to withstand corrosion. The earth electrodes, being directly in contact with the soil or with water, operate in corrosive conditions. There are three main factors that determine the rate of corrosion of metal objects in the soil:

  • DC currents in the earth
  • Chemical contamination of the soil
  • Electrochemical (galvanic) phenomena between various metals located in the soil

The choice of electrode material is usually a compromise between cost and durability of the earth electrode. Corrosion of material and corrosion aggressiveness are the main factors limiting the lifespan of an earthing system.

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