Investigations of Metal-Oxide Surge Arresters for HVDC Circuit Breaker Applications

摘要

Nowadays considerable effort is put into planning/realizing multi-terminal, meshed HVDC transmission networks. With gaining attention one of the crucial components of a multi-terminal HVDC grid is the HVDC circuit breaker. The HVDC circuit breaker must be capable of clearing DC faults without de-energizing the DC side of the grid. Recently, a few HVDC circuit breaker solutions have been proposed, some are realized into prototypes and a few are in operation. Unlike AC circuit breakers, a DC circuit breaker has to deal with special requirements for interrupting a direct current. Extremely fast operation, the creation of artificial current zero(s), the generation of a counter voltage higher than the system voltage and large energy absorption are the major requirements. So far, the energy absorption requirement of a HVDC circuit breaker has not been brought to consideration even though all the proposed technologies of HVDC circuit breakers include an energy absorption component. For this purpose, metal oxide surge arresters (MOSA) are used. But the kind of stress the MOSA has to deal with in a HVDC circuit breaker is not taken into account during the common engineering process for usage in an AC grid. In this paper the requirements of MOSA for HVDC circuit breaker application are discussed. Several columns of stacked MOSA blocks are needed to cope with large energy absorption. Due to the application condition direct current stable metal oxide varistors are used. Features such as current sharing among the columns, temperature rise, energy handling and accelerated aging with accompanying characterization are investigated and results of tests performed under realistic DC fault interruption conditions are presented. The conclusions from the test results provide a better understanding of the requirements and stresses on a MOSA as an energy absorber in a HVDC circuit breaker.