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Development and Field Application of Metallic Return Protecting Breaker for HVDC Transmission

This paper describes the system requirements, circuit and component selections, development and field tests on a metallic return protecting breaker for an HVDC transmission system. Self oscillation phenomenon, generated in the course of DC current interruption by an air blast circuit breaker, is utilized to force the current to zero. Also discussed is outlook for development of an HVDC main line circuit breaker.