When the contacts of a medium-voltage DC air circuit breaker(DCCB) are separated, the energy distribution of the arc is determined by the formation process of the near-electrode sheath. Therefore, the voltage drop thr...When the contacts of a medium-voltage DC air circuit breaker(DCCB) are separated, the energy distribution of the arc is determined by the formation process of the near-electrode sheath. Therefore, the voltage drop through the near-electrode sheath is an important means to build up the arc voltage, which directly determines the current-limiting performance of the DCCB. A numerical model to describe the near-electrode sheath formation process can provide insight into the physical mechanism of the arc formation, and thus provide a method for arc energy regulation. In this work, we establish a two-dimensional axisymmetric time-varying model of a medium-voltage DCCB arc when interrupted by high current based on a fluid-chemical model involving 16 kinds of species and 46 collision reactions. The transient distributions of electron number density, positive and negative ion number density, net space charge density, axial electric field, axial potential between electrodes, and near-cathode sheath are obtained from the numerical model. The computational results show that the electron density in the arc column increases, then decreases, and then stabilizes during the near-cathode sheath formation process, and the arc column's diameter gradually becomes wider. The 11.14 V–12.33 V drops along the17 μm space charge layer away from the cathode(65.5 k V/m–72.5 k V/m) when the current varies from 20 k A–80 k A.The homogeneous external magnetic field has little effect on the distribution of particles in the near-cathode sheath core,but the electron number density at the near-cathode sheath periphery can increase as the magnetic field increases and the homogeneous external magnetic field will lead to arc diffusion. The validity of the numerical model can be proven by comparison with the experiment.展开更多
高压直流故障限流器(fault current limiter,FCL)及断路器(DC circuit breaker,DCCB)在直流电网保护中具有重要作用。该文提出一种具备限流能力、通态损耗低、主限流电路采用晶闸管器件的多端口直流断路器(multiport DC circuit breaker...高压直流故障限流器(fault current limiter,FCL)及断路器(DC circuit breaker,DCCB)在直流电网保护中具有重要作用。该文提出一种具备限流能力、通态损耗低、主限流电路采用晶闸管器件的多端口直流断路器(multiport DC circuit breaker,Mp-DCCB),分阶段对新型拓扑的限流过程及断路过程进行理论解析。分析电压电流应力、避雷器耗能与Mp-DCCB关键参数的关系,给出Mp-DCCB参数设计方法。对所提Mp-DCCB的限流和断路能力进行仿真验证,证明Mp-DCCB可代替多个常规DCCB,并减少对避雷器的耗能要求。展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No.51977132)Key Special Science and Technology Project of Liaoning Province (Grant No.2020JH1/10100012)General Program of the Education Department of Liaoning Province (Grant No.LJKZ0126)。
文摘When the contacts of a medium-voltage DC air circuit breaker(DCCB) are separated, the energy distribution of the arc is determined by the formation process of the near-electrode sheath. Therefore, the voltage drop through the near-electrode sheath is an important means to build up the arc voltage, which directly determines the current-limiting performance of the DCCB. A numerical model to describe the near-electrode sheath formation process can provide insight into the physical mechanism of the arc formation, and thus provide a method for arc energy regulation. In this work, we establish a two-dimensional axisymmetric time-varying model of a medium-voltage DCCB arc when interrupted by high current based on a fluid-chemical model involving 16 kinds of species and 46 collision reactions. The transient distributions of electron number density, positive and negative ion number density, net space charge density, axial electric field, axial potential between electrodes, and near-cathode sheath are obtained from the numerical model. The computational results show that the electron density in the arc column increases, then decreases, and then stabilizes during the near-cathode sheath formation process, and the arc column's diameter gradually becomes wider. The 11.14 V–12.33 V drops along the17 μm space charge layer away from the cathode(65.5 k V/m–72.5 k V/m) when the current varies from 20 k A–80 k A.The homogeneous external magnetic field has little effect on the distribution of particles in the near-cathode sheath core,but the electron number density at the near-cathode sheath periphery can increase as the magnetic field increases and the homogeneous external magnetic field will lead to arc diffusion. The validity of the numerical model can be proven by comparison with the experiment.
文摘高压直流故障限流器(fault current limiter,FCL)及断路器(DC circuit breaker,DCCB)在直流电网保护中具有重要作用。该文提出一种具备限流能力、通态损耗低、主限流电路采用晶闸管器件的多端口直流断路器(multiport DC circuit breaker,Mp-DCCB),分阶段对新型拓扑的限流过程及断路过程进行理论解析。分析电压电流应力、避雷器耗能与Mp-DCCB关键参数的关系,给出Mp-DCCB参数设计方法。对所提Mp-DCCB的限流和断路能力进行仿真验证,证明Mp-DCCB可代替多个常规DCCB,并减少对避雷器的耗能要求。
