Modelling of special protection systems for power system dynamic simulations

Special protection systems (SPSs) are very important for the safety and stability of large-scale power systems. A more accurate assessment of system security can be achieved if SPS models are constructed to conform to the actual situation of power grids. However, it is difficult to realistically simulate the performance of SPSs for a large-scale power system. Based on virtual relays and ladder diagrams, this paper proposes a general modelling method for SPSs that conforms to their actual characteristics. Moreover, the full dynamic calculations including these models can be realized using this approach. The modelling process is significantly simplified and the computing work is considerably reduced using the new method. The results show that the simulation program, including the SPS models, can more accurately represent the dynamic performance of a power system after a disturbance, especially during cascading outages caused by power flow transfers. The method can be a useful tool for accurately analyzing the dynamic stability of power systems.