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Transformer Differential Protection (87T)

Percentage-bias (percentage differential) restraint characteristic check — dual-slope operate curve consistent with IEEE C37.91 transformer protection guidance.

AAJappsEngineering Calculation Report

Transformer Differential Protection (87T)

Percentage-bias principle, IEEE C37.91-consistent

Generated

For preliminary engineering use only — always verify results against project-specific standards and a qualified engineer's review before use in a real design.

CT-secondary currents (common base, p.u.)

I1 (into transformer)

p.u.

I2 (out of transformer)

p.u.

Restraint characteristic

Minimum pickup, Id0

p.u.

Slope 1

Knee restraint current

p.u.

Slope 2

87T restraint check

Differential current, Id0.0700 p.u.

Restraint current, Ir1.0150 p.u.

Operate threshold at this Ir0.5537 p.u.

TripsNO ✓