Calculating the Capacitive Current Flowing Off from an Overhead Power Line Energized with the Voltage Induced by the Influencing Overhead Line Located at Different Distances from the Former

Abstract

Accidents that happen in carrying out maintenance and repair of overhead power lines account for the largest share in the statistics of injuries occurring in the electric power industry. Electric shock received by a person as he or she touches a conductor energized with induced voltage is one of injury causing factors. To assess the danger of being injured by induced voltage when the power line taken out for repair is grounded at one place, a numerical analysis was carried out for the influencing line and the line energized by the induced voltage belonging to different voltage classes with the disconnected line situated at different distances from the influencing one, and for the minimal distance between the lines when the influencing and disconnected lines are suspended to a common two-circuit support. It has been found from an analysis of the obtained values that the capacitive currents in the grounded wires decrease with increasing the distance between the influencing overhead power line and the line energized with induced voltage. The total current through the support used as the grounding conductor is higher than the current in any phase and is close to the algebraic sum of phase currents. Therefore, with the supports spaced to a significant distance from each other, it is inefficient to make grounding at the repair team working place. In this case, a more reliable result in terms of ensuring safe working conditions is obtained by individually grounding each phase.An analysis of the calculation results obtained for double-circuit overhead power lines has shown that, in order to ensure safe working conditions on the line energized with induced voltage, for double-circuit supports it is more efficient to ground all phases to the support, because the total current through the grounding conductor in the case of grounding at the work execution place is smaller than the largest current flowing from one phase. In view of the fact that the labor safety rules in operating electrical installations allow the grounding to be imposed at one place in carrying out work on overhead power lines energized with induced voltage, it is worthwhile to include calculations of capacitive current for such case in the Methodical Guidelines for assessing the safety of work carried out under induced voltage to reduce injuries to the personnel servicing overhead power lines.