Grounding and Earthing Systems: Design Guide for Industrial Projects

In North America, 'grounding' refers to connecting to earth for safety, while 'bonding' connects conductive parts together.

In IEC standards, 'earthing' is the general term. The system type (TT, TN, IT) defines how the earthing is arranged.

For international projects, use IEC terminology: TT, TN-S, TN-C, TN-C-S, IT systems.

TT system: Transformer neutral grounded at source, equipment grounded locally. Used in rural areas, old installations.

TN-S system: Separate neutral and protective conductors throughout. Best for industrial plants, data centers.

TN-C system: Neutral and protective combined (PEN). Older installations, not recommended for new projects.

TN-C-S system: Combined at source, separated downstream. Common in residential areas.

IT system: Isolated neutral (or high impedance grounded). Used in hospitals, mines (continuity of service).

Copper rods: Most common, 2-3 meters deep, interconnected with bare copper conductor.

Copper plate: Used in rocky soil, buried horizontally.

Chemical earthing: Uses conductive compound, good for high resistivity soil.

Ring earth: Copper strip around the building, connected to all electrodes.

Resistance requirement: Typically <5Ω for substations, <10Ω for industrial plants, <30Ω for residential.

Earth resistance test: Use 3-point method (Wenner method) or clamp-on tester.

Continuity test: Verify all bonded parts are connected.

Step and touch voltage: Critical for substations (human safety).

Frequency: Test after installation, then every 3-5 years.

1. Undersizing earthing conductor (causes fire during fault)

2. No corrosion protection (electrodes deteriorate quickly)

3. Mixing earthing systems (causes circulating currents)

4. No inspection access (cannot test after installation)

5. Ignoring soil resistivity (one rod not enough in high resistivity soil)