Whenever it is necessary for wires crossing other wires of a different potential, if possible the higher potential should be carried above the lower potential wires and the poles of both lines shall be extra heavy and of substantial construction, and under all conditions there shall be at least three feet (3') between such wires and where possible the lines so built and constructed that should a wire of the upper line break at the pin or become detached it cannot in falling come in contact with the wires below. If nets or other similar devices are employed, the nets or devices shall be grounded and all ground wires shall be of a size that will easily carry the full current of the wires of the highest potential. (Prior code § 8-4-14)