Investigation on volt-ampere characteristic of secondary arc burning in atmospheric air

Abstract

The secondary arc, as a common phenomenon in a high voltage power transmission system, is an essence of an electric arc. It not only damages the electrical power equipment but also threatens the safety of the power system. A series of experiments on the secondary arc have been conducted in this work. The volt-ampere curves are measured, the motion trajectories are captured, and the centroid of the secondary arc body is calculated by means of image processing. The experimental results indicate that the secondary arc length can reach several meters, and its volt-ampere curve is completely different from that of short-gap arcs and others operated in some special dielectrics such as vacuum. The evolution of the secondary arc can be generally divided into two stages. In the early stage, the arc column performs a vertical motion and has an upward trend due to thermal buoyancy. Basically, the volt-ampere curve has a shape of a regular hysteresis loop. The impacts of the frequent short-circuit behavior of the arc column on the volt-ampere curve and arcing time are investigated. At the later stage, the secondary arc temperature drops and the zero-off behavior becomes obvious. The volt-ampere curve is inevitably affected. The zero-off duration is obtained, and the key factors are discussed. The dynamics of charged particles in the zero-off interval are analyzed. Furthermore, under the effect of strong wind, it has been found that the secondary arc current is occasionally forced to zero and preceded by the voltage. The mechanism for such a phenomenon is first elucidated from the perspective of energy balance. The results lay a theoretical basis for secondary arc physics.