Ground Grid
How is ground grid integrity verified?
Pass 300 A DC through the grid between a reference point and test ground; record voltage drop: less than 1.40 V = good, 1.41–2.79 V = safe but weakened, greater than or equal to 2.80 V = bad.
What defines safe step/touch potential limits?
IEEE Standard 80-2000 defines thresholds for 50 kg/70 kg persons; step voltage = surface potential difference between feet 1 m apart.
Can a high-resistance grid still be safe?
Yes, if design mitigates step/touch hazards (e.g., increasing surface material thickness) without expanding the grid.
What materials are selected for ground grids?
Components must be electrically conductive, corrosion-resistant, have adequate current capacity, and be mechanically strong.
A ground grid is an engineered network of interconnected conductive materials (typically copper or galvanized steel) buried in the soil to provide a low-resistance path for fault currents to safely dissipate into the earth, preventing dangerous voltage build-ups that could harm equipment or personnel.
In ServiceGrid (CMMS/Asset Reliability) contexts, ground grids are maintained by tracking grid continuity tests, step/touch potential measurements, and conductor resistance checks to ensure the grid maintains less than 5 Ω resistance to remote earth. This prevents fatal electric shock during faults like short circuits or lightning strikes, ensuring safety for personnel and equipment on the shop floor.
Open-circuit conductors or deteriorated connectors causing high-resistance connections that prevent current flow during faults.
Inadequate design/installation failing to mitigate available fault current, leading to unsafe step/touch potentials (e.g., greater than 2.80 V drop indicating a bad grid).
Corrosion or erosion of buried conductors over time without proactive testing, increasing impedance and risking equipment failure or personnel injury.