Protection - Selectivity Check

Protection selectivity check - downstream breaker must trip before upstream for faults on its branch.

ProtectionSelectivityRelay

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This calculator requires JavaScript to compute its result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

\Delta t \geq 100\,ms

Symbol	Meaning	Unit
$Δt$	Time grading margin	ms

Source: IEC 60255 / ABB Selectivity

Protection selectivity check - downstream breaker must trip before upstream for faults on its branch.