Q: Why do some experts say ground rods won’t work to trip a circuit?
A: The experts say this because they are right depending on the conditions, which we’ll soon discuss. But let’s start with a definition of the idea of “remote ground” as the point at which we connect a protective system to earth. The lower the resistance of that remote ground connection to earth, the more current flows and the faster a fault clears. So, what we should be doing as a rule is using the best available ground to remote earth. The problem is that we often overlook a key element in this debate, which is that the ground source is not what protects the worker. The ground path trips the circuit. Bonding the worker into the ground scheme – the path between the fault and ground – is what provides reliable protection for workers using personal protective grounds. For example, if you ground to a system neutral, you have connected to a very low-resistance path, but you also are connecting to a current-carrying conductor. If workers are not bonded into the ground scheme, they can be exposed to current from the neutral that can result in voltage rises across the ground scheme, especially if a fault current rises on the neutral from some remote event on the system. If you are on a delta primary system at a transformer bank, that neutral on the secondary side is derived from the ground rod at the foot of the pole. Nobody would take their truck ground up to the neutral bushing of a 300-kVA 277/480 bank, but that’s no different than connecting to the ground rod bonding that 480-VAC neutral to earth. That is why delta system workers use ground rods, and to good effect if the conditions are right.