Dynamic state estimation based transmission line protection

Abstract

This thesis proposed a dynamic state estimation based protection algorithm for the transmission line to 1) eliminate complex protection settings in order to prevent human errors, 2) fulfill the protection gaps caused by legacy protection functions, and as a result, reduce relay misoperations. The dynamic model of the line is first converted into an equivalent algebraic companion form by quadratic integration. Then three dynamic state estimation algorithms and the protection logic based on the estimation results are introduced for the protection purpose. The proposed algorithm is compared with legacy protection functions in test cases to demonstrate the effectiveness of the proposed algorithm in high impedance fault case, external close fault case, current reversal case, current inversion case, voltage inversion case, etc. The impact of instrumentation error to the algorithm is also investigated and integrated modeling of transmission line and instrument transformers is proposed to improve the robustness of dynamic state estimation based protection. The sensitivities of the algorithm related to modeling errors and synchronization errors are also analyzed.