🛡️ IEEE C37.91 Protection (87T Restraint Curve, CT Saturation Harmonic Inrush)

Transformer Differential (87T) Protection Calculator

Configure microprocessor numerical transformer differential protection relays (SEL-387 / SEL-787 / GE Multilin T60) under IEEE C37.91: calculate percentage restraint dual-slope curves ($Slope_1 = 25% ext{ to }35%$, $Slope_2 = 50% ext{ to }70%$), coordinate 2nd harmonic inrush blocking ($15% ext{ }I_2/I_1$) and 5th harmonic overexcitation restraint, and protection profits.

1. Project & Operating Inputs

Transformer Primary Voltage (kV e.g. 34.5 kV Medium-Voltage Primary)

Transformer Capacity (MVA e.g. 15.0 MVA Substation Transformer)

Customer Invoiced Relay Coordination & Commissioning Fee ($)

SEL-387 Relay Package, Doble Secondary Injection Test Set, Lead PE ($)

2. Financial Breakdown & Yield

IEEE C37.91 87T PROTECTION

Turnkey Substation Protection & Relay Study Profit

Power System Protection Engineering Margin

0.0%

Gross Revenue / Bill

Total Project CapEx

Operating / Direct Cost