This installation of “Train the Trainer 101” may have an odd title, but it was inspired by some recent conversations I’ve had. I’ve learned a lot about personal protective grounding (PPG) in the past 20 years, and I continually learn even more as others share their research and experiences. Some time ago I learned that much of the fundamental electrical math upon which electrical circuit theory is based does not adequately explain the risk from high currents imposed on grounded systems. That does not mean there are not theoretical explanations for all of the results in high-current fault testing. But the simple circuit math of Ohm’s law cannot explain the complex electrical physics that occur in a high-current fault, and that is partly what confuses the issue concerning EPZ.
What is simple is this fundamental of worker protection: It takes 50 volts to break the electrical resistance of a worker’s skin. If you can break the electrical resistance of the skin, current can flow, and the worker can be injured. However, if voltage cannot penetrate the skin, current cannot flow. You cannot eliminate system current by grounding; you can only divide it (i.e., send most of it through a different path) and hope for the best. But you can eliminate voltage in the worker exposure. You eliminate voltage potential by bonding. Once you’ve eliminated the voltage potential hazard, current no longer matters and thereby the risk is altogether eliminated.