Breaking Through Saturation: Enhancing Line Differential Relay Sensitivity with Optical Current Transformers

The operational integrity of power systems relies heavily on the effectiveness of protection, automation, and control systems. This paper investigates the potential of optical current transformers to enhance power protection performance through optimal parameter settings, aiming to mitigate the limitations associated with electromagnetic current transformers, namely a saturation effect that leads to measurement inaccuracies during transient events. By contrast, optical current transformers offer saturation immunity, ensuring reliable performance even under extreme conditions. To facilitate this investigation, a custom Electromagnetic Transient Program is developed as an AC three-phase power system that operates as a Python script via a Command Line Interface. At this stage, our custom electromagnetic transient program enables the simulation of faults in transmission lines, dynamic modeling of electromagnetic current transformers, optical current transformers, and line differential protection to meet research purposes. Simulation results with comparative analysis demonstrate that line differential protection can be tuned much more sensitively when working with optical current transformers rather than with electromagnetic current transformers. The paper concludes with a discussion of the findings and potential avenues for future research.