An Experimental Study of Short-Circuit Current Making Operation of Air Medium-Voltage Load Break Switches

Abstract

Replacing SF6, the most potent greenhouse gas, with an alternative gas is a challenge faced by medium-voltage load break switches (MV-LBS). Air is a possible alternative, but there are some challenges regarding low dielectric strength leading to high arcing time and dissipated energy. Therefore, understanding the switching processes for both interruption and making operations in air MV-LBS is crucial to designing efficient compact switchgear. This work focuses on making operations in air MV-LBS. A synthetic test circuit and a model switch are designed based on the standards to simulate making operations under fault conditions similar to a real test. The test condition is set to achieve high prestrike arcing time and energy. The results show that the most destructive impact of the making short-circuit current occurs in the first half-cycle of the load current when the pre-strike arc is formed. With an average short-circuit current with a peak of 22 kA and a breakdown voltage of 20 kV, the switch failed to re-open due to the arcing contacts welding after four successive making operations without main contacts and seven successive operations with main contacts. It has been shown that the total arcing contact mass loss occurs mainly during the pre-arcing time. Increasing the closing speed could be a possible solution to minimize the impact of arcing. Index Terms-medium voltage (MV), load break switch (LBS), making operations, contacts erosion, arcing contacts, main contacts, arc erosion.

Experimental Validation of the Adiabatic Assumption of Short-Circuit Tests on Bare Conductors

“…In order to validate the accuracy of the adiabatic approach, the results presented in this section assume a target temperature at the end of the short-circuit duration of 250 ºC, although some standards (e.g. IEC 62271-1 [3]) do not propose a specific maximum temperature at the end of the short-circuit.…”

“…OWER systems are experiencing a steady growth worldwide, thus leading to an increase in short-circuit levels [1]- [3]. Short-circuits are among the most common fault modes in electrical networks, and are complex electromagnetic transient phenomena that have received much attention in the scientific field [4].…”

A Model to Calculate the Current–Temperature Relationship of Insulated and Jacketed Cables

“…The demand for electrical energy is currently growing worldwide [ 1 , 2 , 3 ], so power systems load levels are increasing. It is of paramount importance to ensure that power cables operate within their thermal limits to not compromise their safe operation.…”