An Algorithmic Approach for Identifying Critical Distance Relays for Transient Stability Studies

TL;DR

This paper introduces an algorithm that efficiently identifies critical distance relays for transient stability studies, reducing the need to model all relays and improving accuracy in power system stability analysis.

Contribution

It proposes a novel algorithm using impedance monitoring and voltage evaluation to select critical relays, enhancing modeling efficiency in stability studies.

Findings

The algorithm accurately identifies critical relays in the WECC system.

Modeling only the critical relays suffices for reliable stability assessment.

The approach reduces computational complexity without sacrificing accuracy.

Abstract

After major disturbances, power system behavior is governed by the dynamic characteristics of its assets and protection schemes. Therefore, modeling protection devices is essential for performing accurate stability studies. Modeling all the protection devices in a bulk power system is an intractable task due to the limitations of current stability software, and the difficulty of maintaining and updating the data for thousands of protection devices. One of the critical protection schemes that is not adequately modeled in stability studies is distance relaying. Therefore, this paper proposes an algorithm that uses two methods to identify the critical distance relays to be modeled in stability studies: (i) apparent impedance monitoring, and (ii) the minimum voltage evaluation (MVE). The algorithm is implemented in Python 3.6 and uses the GE positive sequence load flow analysis (PSLF) software for performing stability studies. The performance of the algorithm is evaluated on the Western Electricity Coordinating Council (WECC) system data representing the 2018 summer-peak load. The results of the case studies representing various types of contingencies show that to have an accurate assessment of system behavior, modeling the critical distance relays identified by the algorithm suffices, and there is no need for modeling all the distance relays.