Why can a relay trip twice for the same fault, even when its coordination "looks fine on paper"? It's one of the questions clients ask us most, and the answer almost always comes down to a detail a poorly verified selectivity study lets slip through. In this article — and the video that goes with it — we audit and correct a real case using RTC2 (Relay Tripping Curves PRO2), applying the IEEE Std 242 criteria (the "Buff Book"). This isn't just a case story: it's also a practical guide to...

SIPROTEC 4 vs. SIPROTEC 5 in ETAP: same curve name, different formula Can the same curve name mean different trip times? That's what I found while reviewing a coordination study in ETAP: modeling a Siemens SIPROTEC 5 relay with the "ANSI Extremely Inverse" curve, the curve came out much higher than expected. Comparing the times the software produced against the manufacturer's own manual, they didn't match — instead, they matched the previous generation, SIPROTEC 4. To confirm whether the...

Conceptual image of a generator similar to the GT-7 This report documents the optimization of generator protection carried out on GT‑7, addressing the comprehensive redesign of the protection system and the following key aspects: ✅ Selection and implementation of the Siemens 7UM622‑55EB093CG0 relay ✅ Detailed configuration in DIGSI 4, with CFC logic and ANSI functions 51V, 81, 59, 46, 87G, 64G, 64S, 40, and 32P ✅ Analysis of real fault events in the network, with oscillographic and vector...