Date of Award


Document Type


Degree Name

Master of Science (MS)


Electrical and Computer Engineering (Holcomb Dept. of)

Committee Chair/Advisor

Dr. Sukumar Brahma

Committee Member

Dr. Johan Enslin

Committee Member

Dr. Ramtin Hadidi


The transition towards clean energy initiatives to reduce global greenhouse emissions and the dependence on fossil fuels requires the interconnection of large-scale renewable energy power plants to high voltage transmission networks via inverters. These inverter interfaced power sources, popularly known as inverter-based resources (IBRs), pose several technical challenges to the existing distance protection infrastructures widely deployed in transmission systems.

Fault characteristics of IBRs are significantly different from those shown by synchronous generators (SGs). With IBRs taking a large share of generation, their increasing penetration at the transmission level causes incorrect operation of existing distance protection schemes designed for systems dominated by SGs. This work focuses on the impact of inverters on negative sequence component-based directional elements that assist distance relays in identifying the direction of fault current, causing incorrect tripping of relays and missing out on in-zone faults. The main reasons for these misoperations are the negative sequence current blocking function in inverters and the changed angular relationships between the sequence voltages and currents dictated by the IBR control schemes.

This work proposes a solution that uses the method of fault direction identification used in classical non-numerical relays to address this problem. Unlike modern numerical relays, directional elements in non-numerical relays use the measurements of phase voltages and currents instead of negative sequence components. This work shows that the method of direction identification used by non-numerical relays still works accurately in all test scenarios, including cases with IBR feeding the relay, where the negative sequence component-based method in modern numerical relays fails.

Author ORCID Identifier




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