Experimental Study of Arc Motion Near Splitter Plates in Low-Voltage Switching Devices

Abstract

Switching performance of a low voltage switching device (LVSD) is determined by limiting current and stopping re-ignition. This is strongly influenced by how the arc moves inside the LVSD quenching chamber during the switching process. Improved switching performance is achieved when the arc quickly enters and stays inside the splitter plates of the LVSD, with the arc attached to the surface of the plates.This paper studies arc motion around splitter plates in LVSDs and the correlation with arc voltage. Arc motion is investigated using a high-speed optical arc imaging system (AIS). It is observed that the arc fluctuates as it enters the splitter plates, with periods inside the plates followed by sudden re-strikes of the arc roots outside the plates. The AIS system allows the measurement of arc displacement and a correlation with the arc voltage. The results show two phases, with a narrow correlation while the arc in the chamber out of the splitter plates and a distributed correlation while in the splitter plates. Further a new performance parameter the splitter time (ST) ratio is defined. The influence of the ST ratio on the chamber vent design is investigated. It is found that with wider and well distributed vent apertures the ST ratio is higher than with a closed vent, and arc motion on entry to the plates is improved.