Comparative research into transients by switching of high voltage shunt reactor

•Transients during controlled switching of 123kV shunt reactor are investigated.•Results of field measurements and computer simulations are presented.•Effects of different values of chopping-current during switching-off are considered.•Inrush currents strictly depend on accuracy of circuit breaker (CB) drive mechanics.•Overvoltages were lower for motor-driven CB than for hydraulically operated CB. This article deals with results of performed studies of transient phenomena in application of controlled switching technique by switching high voltage 123kV, 100MVAr shunt reactor. First, for switching a single-pole hydraulically operated SF6 circuit breaker has been selected and after that, one with electric motor-drive. In preparing of experimental part of studies the EMTP-ATP software has been used in computer simulations, further for analyses the cases of optimal controlled switching and switching within time deviation limits. For simulation of uncontrolled switching with current chopping and arc-reignition dynamic model of arc behavior has been implemented. The field tests with both circuit breakers have been repeated in similar network conditions for further statistical analyses. During some tests, the transient phenomena of uncontrolled switching have been observed. The achieved experimental results were compared with the computer simulations.