Evaluation of Gas Insulated Disconnector Switch for Bus Charging and Bus Transfer Currents

Abstract

Abstract Gas insulated disconnector switches (DSs) are employed in a gas insulated substation (GIS) to interrupt and to make capacitive currents, in principle. During switching of capacitive currents very fast transient over-voltages (VFTOs) are common to DS. Intense VFTOs may result in peak voltage close to basic insulation level (BIL) of the connected equipment, leading to progressive deterioration and secondary breakdowns in very high voltage gas-insulated systems. At the same time, arcing during switching of bus transfer currents, by the DS, is considered as a source of substantial amount of decomposed products. This contamination may result in significant reduction in insulation strength of the medium. In order to ensure reliability of the design, it is essential to establish the DS for bus charging and bus transfer current duties under most onerous service conditions through suitable tests. The optimal design of DS to meet these test duties is established with suitable analytical techniques. The tests, which have been discussed and analyzed as part of this study, were performed on an indigenously developed 145 kV gas insulated DS as per IEC 62271-102. A detailed arrangement of the DS (main and auxiliary) and guidelines for conducting the above tests are also explained. Different performance parameters like arcing time, pre-arcing time, secondary discharges, trapped voltages, and level of contamination are analyzed. The behavior of DS during these evaluations is also reported in the present paper. Finally, the effect of different design parameters on performance of the DS has been analyzed.