Protection of Transmission Lines

Abstract

This chapter presents two examples of the MM-based method used for protection of transmission lines. One is concerned with an adaptive distance relaying algorithm (ADRA) designed for transmission line protection. In ADRA, a morphological fault detector (MFD) designed based on MM is used to determine the occurrence of a fault. The Euclidean norm of the output of the MFD is then calculated for fault phase selection and fault type classification. With respect to a specific type of fault scenario, an instantaneous circuit model applicable to a transient fault process is constructed to determine the fault location. The distance between the fault location and the relay position is calculated by a differential equation of the instantaneous circuit model, which is resolved in a recursivemanner within each sampling interval. Due to the nature of recursive calculation, the protection zone of the relay varies from a small length to a large one, which increases as the accuracy of estimated fault distance improves when more samples are involved in the recursive calculation after the fault has been detected. The other example is concerned with the problem of mis-selection of a fault phase during a fault occurring on a double circuit transmission line. This problem is caused by the interaction between the phase lines of the two circuits, due to their mutual coupling. An MM-based fault phase selection scheme is introduced to accurately classify the fault types [92]. In this scheme, the fault characteristics can be effectively extracted from the associated currents by MGW. The fault phase selection scheme is evaluated on a simulation model under different fault types, locations, ground-fault resistances and inception angles.