IEC 60056: High-Voltage AC Circuit-Breakers (Legacy Standard)

Legacy Breaker Nameplates: Understanding IEC 60056 vs. IEC 62271-100

IEC 60056 (superseded by IEC 62271-100) was the legacy HV AC circuit-breaker standard. Many breakers commissioned between 1990–2005 still carry IEC 60056 nameplate ratings. Understanding the differences between these standards is essential for substation retrofit projects.

Key changes in IEC 62271-100: Added capacitive current switching (Classes C1/C2), reactor switching, and stricter Short-Line Fault (SLF) requirements (L90 replacing L75). A breaker that passed IEC 60056 type testing may not meet IEC 62271-100 capacitive switching requirements — critical for shunt capacitor bank applications.

When reviewing old nameplates: “Rated breaking current I_sc” (IEC 60056) → “Rated short-circuit breaking current I_k” (IEC 62271-100). Test duties TD1–TD5 have also changed — TD4 (terminal fault) TRV parameters are more severe in the new standard.

TN Lab — When retrofitting old substations, never assume a legacy breaker meets all requirements of the current standard.