Modeling of Symmetrical Component Filters in the Logic of Current Directional Zero-Sequence Protection

This article considers the operating principle of the logical part of the residual directional overcurrent protection. Protection stages are triggered by zero-sequence currents that occur due to asymmetric short circuits. The authors present the development of a new component, the zero-sequence filter, in the PSCAD software package. During modeling, the authors developed the functional diagram for the zero-sequence current filter that isolates symmetric components from the three-phase network current. The authors modeled a zero-sequence power direction relay and functional diagrams for two stages of residual directional overcurrent protection. PSCAD can write a COMTRADE file of the transient process and then use RETOM to test the settings and behavior of protection and automation systems. This allows for the evaluation of calculation and aligned the operation of devices in the laboratory.