A new protection scheme to prevent mal-trips due to power swings

New distance protection algorithms based on mathematical logic blocks are introduced in this paper. The algorithms prevent mal-trips due to power oscillations using additional criteria in combination with traditional distance relaying. These additional criteria are based on symmetrical components and the derivative of the phase angle associated with the current as seen by the relay. A simulation is performed in an eighteen bus system developed by the authors where the performance of the algorithms is analysed. No timer settings as is necessary for conventional power swing detectors are needed. Thus different cycle times of the power oscillations will not affect the performance of the algorithms. Neither does an area in the RX-diagram have to be pre-defined which may cause extraordinary difficulties for applications serving long distance transmission lines.