How relevant is stray voltage apart from the electric system?
While the Earth is used by all as the zero-voltage frame of reference, the Earth (as measured between distant points) can be at extreme values distant from zero volts. Due to cloud formations passing overhead, weather related phenomena, geologic stress, solar-magnetic-disturbance-induced ground currents, the voltage at any one point in the soil can be hundred, or thousands, of volts different from another spot. Because of this and the dangers involved, most of the bulk electric power transfer system is operated ungrounded, except for the low voltage side, and that is merely a “local” ground. The residential power distribution can be ungrounded (4800 V), or grounded (most other voltages). Where we measure, and are concerned with, stray voltage / current phenomena, we are dealing with “local” problems, whose range is at most a few miles of convoluted wire or pipe ways. The normal Earth-related stray stuff is natural, and cannot be controlled, but since we exist at an infinitesimally smal
