RelayGuard

RelayGuard is a reference app for anyone working through the basics of electrical protection. Five common device families are covered in plain language: • Fuse: short-circuit clearing through a melting element, with current grading guidance such as the 1.6 : 1 rating step • Circuit Breaker: overload and short-circuit protection with B, C, and D tripping curves, and how series breakers are graded • Residual Current Device: how residual current is sensed, typical 30 mA final circuit settings, and two-stage arrangements with delayed upstream units • Surge Protective Device: lightning and switching overvoltage diversion, Type 1 / 2 / 3 placement, and energy coordination between stages • Thermal Overload Relay: bimetal motor overload protection and its division of duties with fuses and breakers Each device page shows what the device does, its action characteristics, coordination points, and typical reference values. The Coordination section lets you pick any upstream and downstream pair and see a simplified reference result: whether the pair usually supports selectivity, needs a curve check, shares complementary duties, or is not a usual arrangement. Reference points and typical grading ratios are listed with each result. The Basics section collects eight short ideas behind protective coordination, including selectivity, sensitivity, speed, grading margin, current grading, and override tripping. A compare view places any two device families side by side across family, protection target, acting element, reset style, and typical placement. Note: RelayGuard offers simplified reference information for building a basic understanding of protection practice. Always confirm final settings with device datasheets and local installation requirements.