Sukumar Brahma

Presentations:

Power System Protection In Presence of Renewables: Challenges and Solutions

At local protection level, there are documented instances of legacy numerical directional and distance relays failing to identify fault direction when they are fed by an inverter based resource (IBR) – solar, wind or storage. At system protection level, the lack of inertia of IBRs has created a concern about transient stability and the critical clearing time associated with this stability analysis. This presentation will offer comprehensive insight and solutions to these issues.

The local impact is largely because the response to fault from an inverter is radically different than the fault response of a traditional synchronous machine. This presentation will explain the reasons for relay misoperations when fed by IBRs and introduce design, implementation, testing and validation of a completely source-agnostic and system-agnostic paradigm – Time Domain Protection.

To assess the transient stability in presence of renewables, this presentation will explain and illustrate the impact of grid following (GFL) and grid forming (GFM) inverter controls on critical clearing time, substantiated by the physics of transient stability. It will show how GFM controls designed to mimic the behavior of a synchronous machine during fault recovery can actually be beneficial to transient stability due to the much faster control response.

Power System Protection and Big Data – Challenges and Opportunities

“Machine learning (ML) is a promising field that is predicted to improve and even revolutionize many engineering processes. Power systems literature contains a significant number of papers dedicated to furthering applications of ML to different analyses and practices, among them power system protection. After more than fifteen years of published papers, not a single commercial relay uses ML for either primary or backup protection. On the other hand, the quantity and quality of real-time data measured in transmission and distribution systems have increased and this trend is likely to continue. Legacy protection systems have come under scrutiny in recent times due to their uncertain and even unacceptable performance in presence of significant renewable resources. Real-time detection of relay misoperations that compromise the security aspect of protection has always remained elusive to protection engineers.

This presentation will first focus on hurdles that have prevented ML-based protection applications from becoming a commercial reality. Then areas where legacy protection has space for improvement will be highlighted. Finally results from presenter’s NSF-funded project will be shared that illustrate both promises and challenges in developing an ML based application to detect relay misoperations.

Short Circuit Modeling and Analysis of Renewable-Rich Power Systems

Phasor domain short circuit analysis (PDSCA) is performed to calculate fault currents, which in turn helps choose equipment rating and relay settings. Traditionally, power system is modeled as a linear system for this analysis, as generators that are operated in a non-linear fashion (constant PV sources) during normal operation behave as Thevenin sources (linear) during fault. Renewables and storage interconnect with power systems through inverters, and their response to fault is dictated by proprietary controls that make the response inherently nonlinear. Due to this nonlinear response to fault, the assumption of linearity breaks down and new modeling techniques and analytical framework are required. Also, as the fault currents contributed by inverters are comparable to load currents, inclusion of loads (which are nonlinear) into short circuit analysis is required for accurate results. This presentation will show how phasor domain short circuit analysis can be accurately performed in presence of any penetration level of IBRs.