Breaking Capacity of Disconnectors and Earthing Switches Operated in Alternative Gases

摘要

Due to the ever increasing awareness of environmental concerns, the use of SF₆ in high voltage switchgear technology shall be reduced. One possible approach is the use of alternative insulating gases having different properties than SF₆, which may require different switchgear design. The focus of this work lies on the breaking capacity of disconnectors and earthing switches operated in the alternative insulating gases. According to IEC 62271-102, two main switching duties would stress the insulating gas, i.e., switching of higher currents at low voltages and switching of small currents at higher voltages. Investigations of two switching cases (i.e., bus transfer current and electromagnetically induced current switching) will be investigated in two different test setups and test circuits in this paper. Both test circuits and the gas handling concept will be introduced. The generation of the transient recovery voltage and the measurement equipment, the test procedure as well as the mixing process will be explained. The paper will also show, which are the important measurable variables and if they will affect the breaking capability. This work deals primarily with alternative gases consisting of either pure natural-origin gases like synthetic air and carbon dioxide or their mixtures with fluorinated additives. With a closer look to the results of the measurements, the decomposition behavior will be investigated. It will be discussed, in which way the breaking capability will be affected by different parameters like the carrier gas, the mixing ratio, pressure as well as electrical parameters (e.g., current, voltage).