The most common source of damage is from strikes to power and communications lines, which then conduct the surges directly into the equipment. However, with nearby lightning, or lightning which may attach to wires that come into the house via other paths (modes 2, 3, 4 of Figure 1), lightning can generate large currents in the house ground system.įigure 1 – How Lightning Creates Damaging Voltages Inside the Home. Information : For the most common source of lightning damage shown in Figure 1 (as mode 1), with a good surge protector installed at the building entrance (Figure 2 below), indeed, major lightning currents are stopped at the service entrance. Without lightning, in a properly wired house, this impression is correct. The NEC/CEC support this impression by requiring that no AC current pass through the ground wiring, except under narrowly defined exceptions: fault conditions (a line-ground short or leakage), or the action of surge protectors, sending the surge currents into the grounding system. People familiar with electricity frequently accept the idea that “Ground is ground,” i.e., that in a house, especially with a grounding system that complies with the NEC or CEC, all points of the grounding system are at the same voltage.
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