Capacitive current interruption by HV air-break disconnectors with high-velocity opening auxiliary contacts

Air-break disconnectors (DS) in a high-voltage network can interrupt small capacitive currents (e.g., occurring when disconnecting short unloaded transmission lines, current transformers, and so forth). The performance of a device with high-velocity opening auxiliary contacts attached to the DS enhancing the interrupting capability is presented. A series of laboratory experiments is carried out with the interrupted current range between 5 and 27 A. The experimental observations include voltage and current characteristics of the DS, and synchronous optical recording of the arc with a high-speed camera. Electrical and optical data are studied for fail and successful interruptions. The results show: 1) The short arcing time by the fast opening contacts limits the energy input into the arc, enhancing the probability of arc extinction; 2) the contribution to the arc energy mainly comes from the oscillations upon restrike. The energy input to the arc increases with higher breakdown voltage, larger air gap, and higher interrupted current; 3) the arc brightness is synchronous with arc current. With higher interrupted current, the overall arc is brighter and its remnants decay slower. Based on the results, potential successful approaches to increase the interruption capability are discussed.