Modelling of and recommendations for UHV and EHV switching duties

摘要

WG A3.28 finalized its studies on switching phenomena for EHV and UHV equipment in 2013. On behalf of SC A3 the results were published in CIGRE Technical Brochure 570, February 2014. Switching phenomena have been studied by benchmark models of radial and meshed networks of 550 kV and above, including UHV, by simulations of several substation layouts and by collecting experience with commissioning tests and other field tests. A main objective was to verify whether WG A3.22’s conclusions and recommendations to IEC TC 17A, which were mainly based on the detailed information available on the future 1100 kV network in Japan, are still valid when other utilities’ practices would have been applied. WG A3.28 proved that indeed the results from the previous studies are applicable to many other cases. Moreover, by the benchmark model, it was possible to add or change elements that have not been covered by WG A3.22, such as series capacitor banks, phase transposition, four-legged shunt reactors. The second objective was to understand the impact of the various choices with respect to secondary arc extinction, reactive power compensation, auto reclosing sequences, the configuration of the OH-line towers, etc. on switching phenomena. Conclusions on the applications of circuit breakers, disconnectors, earthing switches and high-speed earthing switches (HSES) are presented.The third objective was to collect background information on transformer limited fault (TLF) conditions, a topic already addressed by WG A3.22 for UHV. For voltages from 100 kV up to and including 800 kV, information on voltage drop, fault current, first-pole-to-clear factor, amplitude factor, the transient response of a transformer and the additional capacitance between circuit breaker and transformer has been collected.Recommendations to IEC and to CIGRE SC A3 are summarized, such as for circuit-breakers (especially TLF, unloaded line switching, series and shunt-compensation), for disconnectors (especially for bus transfer current switching to delete the limit of 1600 A and for UHV GIS bus-charging currents), and for the new standard for HSES. Further studies are required to collect more information on transformer surge capacitances, bus transfer currents, series and shunt compensation phenomena, induced current switching and out-of-phase conditions. Most emphasis, however, is on more general conclusions with respect to modelling and the mutual influence of various parameters.