Protection Coordination / TCC Study

Preliminary coordination screening only. This tool does not use a licensed manufacturer curve library like ETAP or EasyPower. The transformer inrush point and through-fault withstand curve use commonly published planning approximations (12×FLA/0.1s inrush; a simplified I²t withstand anchored at 25×FLA/2s) — not the exact IEEE C57.109 category curve. Generic fuse/breaker curves are illustrative shapes, not specific manufacturer curves. Use the "Custom points" device option to plot your actual datasheet curve for a real coordination check. Final coordination must be verified by a qualified protection engineer against manufacturer TCC data and the current IEEE/CSA standards.

Transformer & SystemTag, rating, voltages, impedance

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Equipment tag

Transformer rating (kVA) Impedance, %Z

Primary voltage (V, L-L) Secondary voltage (V, L-L)

Short-Circuit at POIManually entered — matches ETAP/EasyPower utility-contribution convention

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Max. available fault current (kA sym.) Min. available fault current (kA sym.)

X/R ratio at POI

Transformer InrushEnergization inrush reference point(s)

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Point 1 — multiple of FLA Point 1 — duration (s)

Include initial peak point (25×FLA @ 0.01s)

Transformer Withstand Curve (optional)Simplified through-fault I²t approximation

Anchor point — multiple of FLA Anchor point — duration (s)

Protective Device (optional)Generic fuse/breaker shape, or plot your own datasheet points

Device model

Fuse class

Fuse ampere rating (A)

Cable Withstand Curve (optional)ICEA P-32-382 conductor thermal limit

Conductor material

Conductor size (kcmil)

Normal temp., T1 (°C) Max short-circuit temp., T2 (°C)

Result — Coordination Screening

Primary FLA

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Secondary FLA

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Isc at secondary bus

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Inrush point

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Time-Current Curve

log-log, current in amperes, time in seconds

Include Calculation Ledger in report Include OhmZone brand mark in report

Report template (.docx, optional)

Calculation Ledger

clause-by-clause