Max Grounding-Grid Resistance for the GPR Screen (IEEE 80)
The grid resistance that keeps ground potential rise within the tolerable touch voltage.
Example
You enter
- Tolerable touch voltage (V, from step-touch-voltage) 200
- Grid current I_G (A) 200
You get
- Max grid resistance to pass the screen 1.000 ohm
Checked against published worked examples from: IEEE Std 80 (ground potential rise).
Details, formula, and sources
ScopeThe inverse of the GPR screen: the grid resistance target that keeps the ground potential rise at or below the tolerable touch voltage, max_R_g = tolerable_touch / grid_current. A 200-V touch limit with a 200-A grid current needs a grid resistance of 1.0 ohm or less to clear the IEEE 80 screen without a full mesh/step study. IEEE Std 80 and a qualified grounding study govern.
Formula or tablemax_grid_resistance_ohm = tolerable_touch_v / grid_current_a, the IEEE 80 GPR screen GPR = grid_current x grid_resistance solved for the resistance that keeps GPR at or below the tolerable touch voltage.
Source and editionIEEE Std 80 ground potential rise, solved for the grid resistance, by name.
Free accessIEEE 80 is available through IEEE; the ground-potential-rise relation is a published grounding-study screen.
What governsEstimate. AHJ and licensed professional govern.
API field namestolerable_touch_v, grid_current_a, max_grid_resistance_ohm
- Resistance target max_R_g = tolerable_touch / grid_current clears the yard without mesh/step analysisIEEE Std 80
- Grid current I_G is the portion of fault current returning through the grid to remote earth, not the total faultIEEE Std 80