A reliability-transient stability analysis of power systems for protection system conditions

This study introduces a transient stability-reliability analysis considering the effects of protection system operation. The analysis considers both the deterministic and the probabilistic parameters. Once the protection system conditions and their parameters are identified, deterministic and probabilistic transition rates are used in order to calculate the transient and steady-state reliability measures using the Markov model of the process. Some transient stability parameters of a specific fault in the system, such as critical fault clearing time and oscillation finishing time are used to determine some deterministic transition rates. For reliability analysis, state probabilities, Loss of Load Expectation, Expected Energy Not Served are calculated for several contingency scenarios taking into account the power flow results obtained by Newton Raphson method. Finally, risk analysis is performed and compared for the aforementioned contingency scenarios. The proposed model is tested on WECC-9 bus system and the results are illustrated.

I. Introduction

Providing high reliability and security plays a vital role in power system operation. In order to assure the system robustness against potential faults, there is a necessity to perform accurate reliability and transient stability analysis. Such an analysis involves considering the effects of protection systems. The main task of the protection systems is to protect the assets of the power system, such as overhead lines, generators, power transformers, etc., against malfunction and destruction. When a fault occurs, the protection system switches to transient state, and its structural and operational conditions affect the behavior of this transient state. In addition, system dynamics should be taken into account in reliability analysis to obtain effective results. Because of the instability caused by large disturbances, cascade failures may be triggered, and eventually the system may go to the blackout [1].