Modeling of protective relay systems for power system dynamic simulations

To solve the problem of lacking of accurate protection relay models in power system dynamic simulation, a general modeling method of protection relay based on “virtual relay” is proposed. A “virtual relay” is a kind of simulation for real relay and defined with rules of logic operation. With hierarchical structure and object-oriented modeling strategy, this method has the advantages of clean logic and convenient modeling, and it´s easy for the users to correct models and expand functions. An open and transparent protective relay model library is developed and dynamic simulation calculation including protection relay models is realized. The simulation results revealed that the dynamic simulation program including protection relay models can represent the dynamic performance of electric power system after disturbance more actually. It can be used to analyze cascading failures caused by incorrect operation of protective relays, replay the accident in a long time after a disturbance in power system, study the essence cause of accident and find the correct fault prevention measures.