In field emission devices, the emission current sometimes degrades with the time. The mechanism of the current degradation is complicated. In this paper, a program is used to simulate the movement of the electron beam...In field emission devices, the emission current sometimes degrades with the time. The mechanism of the current degradation is complicated. In this paper, a program is used to simulate the movement of the electron beam from a field emitter. According to the current distribution and the trajectories of the primary electron beam, it is shown that the residual gas is ionized and the ion pairs are generated. The trajectories of the positive ions are simulated. With the different locations and kinetic energy of i...展开更多
This paper analyzes a DFIG （doubly fed induction generator） WT （wind turbine） fault current after a symmetrical network voltage dip. The goal is to identify the factors determining how fast the first zero crossing...This paper analyzes a DFIG （doubly fed induction generator） WT （wind turbine） fault current after a symmetrical network voltage dip. The goal is to identify the factors determining how fast the first zero crossings of the fault current occur. This is an important subject because the ftmdamental property of the CB （circuit breaker） is that it breaks the current when the current is very near zero. The study was conducted using a hardware-in-the-loop test environment constructed using two real time simulators （dSPACE and RTDS） and a commercial protection relay. It is found that the reactive current injection during a voltage dip demanded by the grid codes enhances the operation of the WT protection because the zero crossings of the currents through CB are attained earlier. In addition, the size of the crowbar resistance has a significant influence on the zero crossings.展开更多
文摘In field emission devices, the emission current sometimes degrades with the time. The mechanism of the current degradation is complicated. In this paper, a program is used to simulate the movement of the electron beam from a field emitter. According to the current distribution and the trajectories of the primary electron beam, it is shown that the residual gas is ionized and the ion pairs are generated. The trajectories of the positive ions are simulated. With the different locations and kinetic energy of i...
文摘This paper analyzes a DFIG （doubly fed induction generator） WT （wind turbine） fault current after a symmetrical network voltage dip. The goal is to identify the factors determining how fast the first zero crossings of the fault current occur. This is an important subject because the ftmdamental property of the CB （circuit breaker） is that it breaks the current when the current is very near zero. The study was conducted using a hardware-in-the-loop test environment constructed using two real time simulators （dSPACE and RTDS） and a commercial protection relay. It is found that the reactive current injection during a voltage dip demanded by the grid codes enhances the operation of the WT protection because the zero crossings of the currents through CB are attained earlier. In addition, the size of the crowbar resistance has a significant influence on the zero crossings.
