Electromigration (EM) is a significant reliability concern in modern circuit design practices that poses a considerable risk to the long-term reliability of contemporary integrated circuits and attracts attention from the EDA industry. Hence, the development of a robust, industrial-level EM analysis tool is crucial. In order to address this challenge, we present PROTON, an open-source tool that can be straightforwardly integrated into industrial design flows covering a wide spectrum of EM analysis needs. On top of this, it offers an intuitive graphical user interface with a high level of automation that allows the visualization of EM stress analysis on power grid designs. The core of PROTON incorporates state-of-the-art methodologies for physics-based EM stress analysis which provide robustness and scalability in handling large-scale power grid designs. These are experimentally verified in comparison with the industrial tool COMSOL on multiple benchmarks where PROTON demonstrated a speedup of �685 with negligible loss in accuracy.