Experimental Platform for Measuring Electrical Discharges in Long Air Gaps With Floating Objects and Its Applications Under Lightning Impulse

Abstract

Long air gaps containing floating objects are common gaps in power transmission and substation projects. Investigating the discharge mechanism of gaps helps improve the power grid operational reliability. This article presents an experimental platform for measuring the electrical discharges in long air gaps with floating objects, which can measure the applied voltage and the discharge current, and capture the images of the discharge process. By analyzing these measured data, the breakdown voltage characteristics of the gap can be explained. In a long air gap with a floating conductive object under lightning impulse, as the floating object moves from the high voltage (HV) electrode to the ground potential electrode, the breakdown voltage first decreases and then increases, producing a minimum breakdown voltage area (MBVA). In this article, the experimental platform was used to explain the formation of MBVA as an application example. The results show that the formation of MBVA is related to the timing relationship between the breakdown of sub-gap 1 and the discharge in sub-gap 2 entering the final jump. The minimum breakdown voltage occurs at the shortest sub-gap 1 ensuring that the discharge in sub-gap 2 enters the final jump just as sub-gap 1 is broken down.