Experimental investigation on ablation-assisted current interruption - Experimental setup and preliminary results

Abstract

This paper presents a flexible setup to investigate ablation-assisted interruption of load currents. The electrical test circuit is grid connected with a transformer secondary voltage from 6.9 kV to 24 kV. The applied stress to the switching device, such as load current amplitude and transient recovery voltage amplitude and shape, can be set to a large range of values by adjusting the circuit components–resistors, reactors and capacitors–in fine steps. A parallel capacitive-resistive voltage divider ensures high bandwidth and low offset voltage measurements. A resistive shunt is used for current measurement and, in addition, a post-arc current sensor is dedicated to the exact measurement of currents lower than 3 A. The high quality of the measurements allows for a detailed study of the extinction voltage peak, current trace prior to current zero and the post-arc current. Load current interruption measurements from one forced airflow switch and two ablation switches are presented and compared. The ablation switches have a clear current limiting effect close to current zero, whereas the air switch gives a linear decline of the current to zero. One of the ablation switches sustains a post-arc current for 7 ms, without experiencing a re-ignition.