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Earthing system or grounding system connects specific parts of that installation with the Earth's conductive surface for safety and functional purposes. The point of reference is the Earth's conductive surface. The choice of earthing system can affect the safety and electromagnetic compatibility of the installation. Regulations for earthing systems vary considerably among countries, though most follow the recommendations of the International Electrotechnical Commission. Regulations may identify special cases for earthing in mines, or in hazardous areas of industrial plants.
1 Electrical earthing
1.1 Protective earthing
1.2 Functional earthing
2 Low-voltage systems
2.1 IEC terminology
2.1.1 Types of TN networks
2.1.2 TT network
2.1.3 IT network
2.2 Comparison
2.3 Other terminologies
2.4 Resistance-earthed neutral (India)
2.6 Earth connectivity check
3 HIGH VOLTAGE SYSTEM EARTHING
Single Ground Electrode
Ground plate
Multiple ground electrodes
Mesh Network
Three families of earthing arrangements, using the two-letter codes TN, TT, and IT.
The first letter indicates the connection between the earth and the power-supply equipment (generator or transformer):
"T" — Direct connection of a point with earth
"I" — No point is connected with the earth, except perhaps via a high impedance.
The second letter indicates the connection between earth or network and the electrical device being supplied:
"T" — Earth connection is by a local direct connection to earth (French: Terre), usually via a ground rod.
"N" — the neutral connection is supplied by the electricity supply network (French: neutral), either separately to the protective earth (PE) conductor or combined with the protective earth (PEN) conductor.
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