To really clarify it you could hammer the point that Earth grounding by itself, called Peg Grounding, it a known predicable cause of fatalities.
"The primary cause of this accident was improper installation and/or maintenance of the low pressure oil gauge switch box. Contributing to the cause of the accident were the following:
- The lack of frame grounding for the junction box.
- The existence of phase to ground faults elsewhere in the system.
- The practice of grounding the equipment through local grounds or "peg grounds".
The use of earth as the safety grounding system has often been referred to as "peg grounding". This term comes about from the practice of grounding each individual piece of equipment on a property with a separate ground rod, driven into the earth. "Peg grounding" therefore, relies upon the earth to conduct ground fault current. The resistivity of earth varies dramatically from location to location as can be seen from test data and published data and does not come close to the resistivity of copper or steel. This system of safety grounding permits multiple faults to occur and persist on electrical equipment that is in close proximity to one another. When this condition occurs, the only other ingredient for a fatality is a person to come in contact with the equipment that has the faults. When a system is being supplied power from a grounded power system and "peg grounding" is employed, a single ground fault is all that is necessary to initiate a potentially fatal situation. As can be seen from this discussion, "peg grounding" should be avoided at all cost."
I have found and fixed this, including at a site that had annual inspections for exactly this. There are more out there.
Referencing the system to Earth, it is just a reference and not a conductor. Any type of overhead wiring including signaling, telephone wires, in a nearby lightning strike even pretty far away, will pick up an induced Voltage enough to jump plasma through the air. The system Earth reference limits this to much less.
Had that happen to me. Bent down to the concrete floor where my tools and materials were and on a clear blue sky day a plasma ball came out of the box and passed right over my back while I was down at the floor. Saw everything light up blue including the concrete floor, had 1/4" of blue fuzz on it for a few seconds. The circuit was a level controller for a water reservoir at the top on the hill, that ran miles down the hill overhead, to the pump.
The State put a 250k $ electronic level controller on it that never worked. No one knew why but they tried. They had me look at it and I told them I could put a timeclock on it, that would fill the reservoir. Thing came right out of the box I was working on and passed right over me while I was bent down. No suitable Earth reference on those signal, control wires.
There is a way to do it right, but it's a specialty.
