Study On Simulation And Experiment Of Short-circuit Breaking For DC Circuit Breaker

In recent years, with development of smart grid, study on DC transmission system gradually increased. In the field of high voltage, DC system has the advantages what AC systems never match. Besides, DC power systems are applied widely in ships, subways and trolleybuses, etc. For the sake of improving the flexibility of DC transmission systems, multi-terminal systems are expected to be adopted to replace double-terminal systems. However, the core component of HVDC circuit breaker, that is used to control and protect the system, still belongs to the technical bottleneck.Through study on a simplified DC system, this paper achieves a comprehensive understanding for difficulties of DC breaking, and makes a summary of current breaking methods and strategies. Comparing the advantages of the existing methods for DC breaking, such as raising an arc voltage, using the passive-resonance method utilizing LC resonance, choosing the commutation principle as the guiding theory of circuit breaker. With the advantages of large breaking capacity. Circuit breakers based on the commutation principle have wide range of applications. Finally, mathematics expressions are given, which can be used as theoretical guidance for the circuit breaker parameters selected.In order to break short faults, a new structure DC-CB based on the commutation is introduced, which puts three vacuum interrupters controlled by a fast repulsive agency. In this way, we can realize the CB's opening, the current's transferring synthetically and the charging circuit removing. By adjusting the length of the rod and the swing angle of crank arm to make sure the moving electrode has reached safe distance to withstand the recovery voltage. It presents a new research direction for development of DC power systems.This paper simulates the process of current transfer by ATPDraw to verify the feasibility of the DC circuit breaker. It also analyzes the commutation circuit parameters effects on the descent rate di/dt before the zero-crossing of the main commutation unit current and the recovery voltage rise rate dv/dt after the zero-crossing.Finally, this paper developed a prototype of 15kV/10kA DC circuit breaker. Breaking experiments of the sample DC-CB are done on LC oscillatory circuit. From the experiment results, the prototype can meet the breaking requirements.