Earthing Conductor Sizing: GI and Copper — Workspace
Galvanized Iron (GI) Earthing and Copper (Cu) Earthing: the conductor cross-section a fault current needs.
What these calculators are for
Two calculators with the same form work out the minimum cross-section of an
earthing conductor for a given fault current and clearing time, and compare
it with the strip you have chosen. One uses a constant for galvanized iron,
the other for copper.
Galvanized Iron (GI) Earthing and Copper (Cu) Earthing
Inputs
Fault level at trafo or panel end — picked from
10000, 25000, 35000, 50000, 55000, 65000, 80000 or 100000, in
amperes.
Disconnecting operating time — 1 to 5,
seconds.
Selected conductor width size — 25, 50, 65, 75
or 100 mm.
Selected conductor thickness size — 3, 6, 10 or
12 mm.
How it is calculated
Surface cross section area (sq.mm) = fault current
× √time ÷ K, where K is 80 for GI and 205 for
copper.
Soil cross section area post corrosion allowance =
that area × 1.15.
Selected conductor cross section area surface =
width × thickness.
Typical use and gotchas
Use it to check an earth strip. The selected strip’s area should
be at least the required area — the area with the corrosion
allowanc…