Node breaker model based transient stability simulations including protective devices modeling and time coordination

Modeling protection devices in the Transient Stability Assessment (TSA) of power systems results in an accurate estimation of system stability and behavior. Miscoordination/misoperations of the relays and circuit breakers (CBs) result in higher order contingencies, >N−1. Substation (SS) configurations and associated CB operations are usually ignored in TSA, even though the relays are modeled in detail. Replicating such scenarios needs manual fabrications in Bus-Branch (BB) models used in commercial TSA tools, which can be eliminated using Node-Breaker (NB) models. Also, incorporating relay algorithms, including the realistic CB operations and coordinating their timings, increases the complexity of the TSA code for large systems. The development of TSA tools to simulate the practical operation of CBs due to protective relay decisions similar to the physical substation operation is essential. This paper attempts in this direction. This paper uses a systematic approach to convert BB models to NB models. The Sparse Tableau Approach (STA) is used to represent the system in the NB model. It provides an algorithmic approach for automatically placing differential, distance and under/over frequency relays. It also gives programming logic to coordinate the timings between relays and the associated CBs. The program complexity increases with the size of the system as the number of CBs and the associated timers significantly increase based on the station configuration. The simulation results demonstrate the scalability and effectiveness of the proposed framework for the WECC 9 bus, New England 39 bus, and Polish 2383 bus systems. The WECC 9 bus system results are compared and validated with the commercial software PSS®E.