Inductive coordination

Inductive coordination

The avoidance of inductive interference. Electric power systems, like almost everything run by electricity, depend on internal electric and magnetic fields; some of these fields find their way into the environment. The strongest of these fields can then induce voltages and currents in nearby devices and equipment and, in some cases, can interfere with the internal fields being used by electrical equipment in the vicinity. These induced voltages and currents, which are due to the coupling between the energized source and the electrical equipment, are called inductive interference. See Electromagnetic induction

Overhead power lines cause practically all of the problems due to inductive coupling. For this reason and for safety considerations, power lines are restricted as far as possible to specific corridors or rights of way. Spacing between them and the requirements of their surroundings are considered and carefully calculated to minimize possible interference. These corridors are often shared by telephone lines, communication circuits, railroads, and sometimes trolley buses, each of which must be considered for possible inductive coupling.

Modern telephone and communication circuits are well shielded and rarely encounter interference from nearby power lines. However, where a long parallel exposure exists, inductive coupling can be reduced by balancing the operation of the power line and by transposition of power and communication lines (see illustration). Fences, long irrigation pipes, and large ungrounded objects within the right of way may experience considerable inductive coupling and must be grounded for safety. See Grounding