Earthing and grounding
- Earth’s ground considered for electrical installations as a reference of 0V - Variable electrical conductivity – naturally electrical currents are flowing.
- Lightning current flowing - Leakage current flowing - Protection of persons (IEC 364 – Electrical Installations of Buildings & IEC 50164 – Lightning protection components)
A properly grounded electrical system serves mainly two purposes:
- It prevents from the risk of electrical shocks to any human being coming in contact with the system.
- It protects the connected equipment from any possible damage occurring due to leakage currents or lightening or voltage surges, by providing a safe passage to these currents to ground. Earthing of an electrical system is achieved by inserting an electrode (plate type / rod type) in to the solid mass of earth and then connecting this electrode to the earth wire coming from the electrical equipment.
- Plate Earthing: A copper plate or galvanized plate is buried in an earth pit below ground level. The plate electrode connects the electrical conductors to the earth.
- Pipe Earthing: A galvanized steel perforated pipe inside the ground connects the electrical conductors to the earth.
- Rod Earthing: Similar to the Pipe earthing. A copper rod replaces the pipe electrode.
- Chemical earthing: Similar to the pipe earthing. A chemical compound material replaces the charcoal and salt layers.
- Service continuity requirement at different voltages
- Safety requirements for humans and equipment
- Possibility of overvoltage
- Maintenance requirements
- Cost consideration
- Soil Resistivity
- Soil Condition
- Dissolved Salt
- Climate Condition
- Physical Composition
- Location of Pits
- Effect of grain size and distribution
- Effect of current Magnitude
Different types of earthing systems are available. Popular methods are:
The choice of earthing method primarily depends on:
Factors affecting Earth Resistivity: