Study on grounding in the vicinity of the work site on 1000-kV power transmission line. Part 2. Electromagnetic induction and its protection

In order to clarify the grounding conditions for protecting workers on a de-energized circuit from induction from a live circuit and to determine the required current capacity of the grounding conductor for a 1,000 kV double-circuit power transmission line, the phenomena caused by electromagnetic induction resulting from a live circuit are discussed. The electromagnetic induction current Ig flowing through the body of a worker and the electromagnetic induction current Ig0 flowing through the grounding conductor can be analyzed by dividing the various power line conditions into three main factors, and using electromagnetic induction current calculations for a power line of infinite length. The zone where Ig does not exceed 1 mA is within 1 km of the grounding point on the de-energized circuit owing to the grounding resistance (0.1Ω) of the substations at the ends of the line and the difference in the phase configurations on the line when the current I1 of the live circuit is a constant 1 kA through the line. Similarly the value of Ig0 is determined by the grounding resistance of the substations at the ends of the line and the difference in the phase configurations on the line. Ig0 is approximately 10 A per 1 kA of I1. The currents Ig and Ig0 produced by electromagnetic induction are additive, allowing Ig and Ig0 in the actual power line to be evaluated by summation.