IEC 60157: Low-Voltage Switchgear — The Foundation Standard for Every Distribution Panel

Low-Voltage Switchgear — The Standard Foundation for Every Distribution Panel and MCC

IEC 60157 series is the foundational standard for low-voltage switchgear and controlgear (later superseded by IEC 60947). Every circuit breaker, contactor, and thermal relay in a building distribution panel — their coordination — the selective operation of cascaded protective devices under short-circuit — is defined by these standards.

Core concept: protection coordination types: (1) Type 1 — equipment may be damaged after a short-circuit, but personnel must not be endangered. (2) Type 2 — no equipment damage permitted (minor contact welding allowed, but contacts must be separable). For critical processes (petrochemical, data centers), Type 2 is mandatory — the controller must be immediately restartable after a fault.