[Willie B]

I think of cow barns. A traditional cow barn the cow is tethered to the stantions. Her water bowl is supplied by iron pipe. Vacuum, milk lines touch her. She stands on a urine soaked concrete floor. Behind her is a barn cleaner. All of these conductive surfaces is connected to a power supply. The definition separating earth grounding from bonding is a bit fuzzy. All of these machines are always wet with electrolyte. Any can contribute voltage.

If the current passes through a cow she suffers.

By connecting earth electrodes to concrete reinforcing steel to electrical neutral, along with bonding all conductive items in contact with the cow, current flows through these wires, instead of the cow.

Earth electrodes are notoriously high resistance. Still they provide a path of less resistance than a human being. Without them there would always be some small potential from center tap to ground.

 

[Willie B]

Excellent point. Sometimes it's easier to put everything at the same potential rather than trying to insulate one from another. Ever notice inside a large electrical substation yard at the base of a manual disconnecting switch. There is a metal pad that is bonded to the support structure that the switch is mounted on. The operator of the switch stands on the metal pad effectively placing his body at the same potential as the switch. In the case of a short of the switch and the structure becomes energized, the operator is at the same potential so no current flows through his body and he is safe.

10-4!!