Using a 300kV puffer-type gas circuit breaker (GCB) combined with a 275kV-1 5OMVA shunt reactor or a test air core reactor at a laboratory, the authors measured surges during reactor current interruption. Such surges as chopping current, single reignition, and multireignition surges were observed. To explain the mechanisms of these surges, the authors measured precisely highfrequency reignition currents with the help of an optical device. Multireignition surges seem unlikely to occur in actual fields.