Skip to main content

Plate earth electrode size numerical

Short answer

Using the plate electrode formula R = (ρ/4)√(π/A) with ρ = 60 Ω·m and required R = 8 Ω, the required plate area is A = π × (ρ / 4R)² = 11.04 m², corresponding to a square plate side of 3.32 m. A single plate of this size is impractical; practical installations use multiple standard plates with treatment.

Calculate the size of the earth electrode for plate earthing system, if the soil resistivity is 60 Ω and required earth resistance is 8 Ω.

For a plate electrode buried vertically, IS 3043 gives:

R = (ρ/4) × √(π/A)

R = earth resistance (Ω), ρ = soil resistivity (Ω-m), A = area of one face of the plate (m²).

The soil resistivity is taken as 60 Ω-m (the unit is printed as Ω). Required R = 8 Ω.

√(π/A) = 4R/ρ
A = π × (ρ / 4R)²
  = π × (60 / 32)²
  = π × (1.875)²
  = π × 3.5156
  = 11.04 m²
Side of square plate = √11.04 = 3.32 m

Check: R = (60/4) × √(π/11.04) = 15 × 0.5333 = 8.0 Ω.

Answer: Area of plate ≈ 11.04 m², i.e. a square plate of about 3.32 m × 3.32 m.

A single plate of this size is not practical. Standard plates (60 cm × 60 cm × 6.3 mm GI) are used in parallel, with charcoal and salt treatment of the pit, or deeper rod/pipe electrodes, to obtain 8 Ω.

✓ Answer checked by Claude Opus 5.5 (high effort)

Related questions

All Industrial Power Distribution and Illumination chapter 2 questions →