With the development of large-scale complicated modern power systems, the requirement for the associated protection scheme tends to be more stringent and its combination more complex. However, it is very difficult to ...With the development of large-scale complicated modern power systems, the requirement for the associated protection scheme tends to be more stringent and its combination more complex. However, it is very difficult to figure out the factors of failure of such systems. This paper proposes a Petri net model of a transmission line protection relaying system, including three types of relays as well as an automatic reclosing device, and shows how to diagnose serial failure of the system by analyzing invariant sets of the model. Furthermore, it gives four basic types of failure sequences and its execution is much more intuitive and effective than the traditional method.展开更多
垂直提升用永磁同步直线电机(permanent magnet synchronous linear motor,PMSLM)在运行过程中受工作环境和控制方式的影响,易出现永磁体局部退磁或均匀退磁故障。为了及时诊断出电机故障,防止电机性能恶化,利用有限元法建立PMSLM模型,...垂直提升用永磁同步直线电机(permanent magnet synchronous linear motor,PMSLM)在运行过程中受工作环境和控制方式的影响,易出现永磁体局部退磁或均匀退磁故障。为了及时诊断出电机故障,防止电机性能恶化,利用有限元法建立PMSLM模型,并对电机局部均匀退磁故障进行仿真。通过改变永磁体的矫顽力实现退磁故障,以得到不同退磁故障状态下的电机永磁磁场、空载反电势、气隙磁密及其谐波、推力、推力波动、电流等特征参数,并进行特性分析。通过对比分析,验证了可采用电机的空载反电势、气隙磁密及其谐波含量作为PMSLM退磁故障诊断的理论依据。展开更多
文摘With the development of large-scale complicated modern power systems, the requirement for the associated protection scheme tends to be more stringent and its combination more complex. However, it is very difficult to figure out the factors of failure of such systems. This paper proposes a Petri net model of a transmission line protection relaying system, including three types of relays as well as an automatic reclosing device, and shows how to diagnose serial failure of the system by analyzing invariant sets of the model. Furthermore, it gives four basic types of failure sequences and its execution is much more intuitive and effective than the traditional method.
文摘垂直提升用永磁同步直线电机(permanent magnet synchronous linear motor,PMSLM)在运行过程中受工作环境和控制方式的影响,易出现永磁体局部退磁或均匀退磁故障。为了及时诊断出电机故障,防止电机性能恶化,利用有限元法建立PMSLM模型,并对电机局部均匀退磁故障进行仿真。通过改变永磁体的矫顽力实现退磁故障,以得到不同退磁故障状态下的电机永磁磁场、空载反电势、气隙磁密及其谐波、推力、推力波动、电流等特征参数,并进行特性分析。通过对比分析,验证了可采用电机的空载反电势、气隙磁密及其谐波含量作为PMSLM退磁故障诊断的理论依据。
