Earthing Plates

Copper has lower contact resistance and a longer service life (40+ years in most soils) — it's the right call for substations, data centres and any critical earthing. GI is cheaper and adequate for general industrial earthing where soil resistivity is below 100 Ω·m and the asset value is modest. Soil chloride and pH matter; share the soil report.

A 600×600×3 mm copper plate or 600×600×6 mm GI plate at 3.0–3.5 m depth in a 600 mm wide brick pit is the working standard in IS 3043. Salt-and-charcoal backfill compound reduces seasonal variation. Depth is what drops resistance fastest — go deeper before going wider.

A 1 MW industrial transformer with separate body, neutral and lightning earthing typically needs 4–6 plate pits in parallel, with the grid loop bonding them. The pit count is set by the touch-and-step voltage calc per IEEE 80 and the soil resistivity. Share the resistivity survey and we'll size it.

The three usual causes are: backfill drying out (no watering arrangement), conductor-to-plate joint corrosion (no tinning, no inspection chamber), and seasonal soil resistivity swings. Vajra plates ship with watering pipe, brass terminal lugs and inspection-chamber drawings — solving all three at procurement.