GridCircuits

Free engineering tools for substation automation, protection & control, SCADA, RTU and transmission engineers. Tools include relay curves, CT sizing, distance and differential settings, coordination, transformers, fault current, power flow, reactive compensation, voltage drop, Ohm's law and conductor sizes. Every tool shows its formula and standard clause, runs in the browser, and never uploads project data. Built for utility and integrator engineers in the US and Canada, IEEE/ANSI first with IEC methods alongside. An IEC 61850 Functional Description Builder is in development.