Earth Fault Loop Impedance Calculation Record (Excel)
Free download · Excel (.xlsx)
Record earth fault loop impedance (Zs) calculations with this Excel template. Captures circuit reference, protection device details, required disconnection time (0.4s or 5s), maximum Zs from BS 7671 Tables 41.2–41.4, conductor resistances (R1 and R2 per metre), cable length, calculated circuit impedance, external loop impedance Ze, total Zs, temperature correction factor, and pass/fail against the standard limit. Essential for verifying automatic disconnection of supply per BS 7671 and IEC 60364-4-41.
What's Included
How to Print
- ●Open in Microsoft Excel 2016+, Google Sheets, or LibreOffice Calc
- ●Add your company logo and project details to the header
- ●Copy data rows to add more circuits or equipment
- ●Print on A4 or A3 landscape for site records
- ●Keep completed records for design verification and audit trail
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Frequently Asked Questions
What is an earth fault loop impedance calculation?
An earth fault loop impedance (Zs) calculation verifies that the total impedance of the fault loop is low enough for the protective device to disconnect the supply within the required time (0.4s or 5s) per BS 7671 Regulation 411.3 and IEC 60364-4-41. It is essential for electrical safety.
What should a Zs calculation record include?
Key fields include circuit reference, protection device type and rating, required disconnection time, maximum Zs from BS 7671 Tables 41.2–41.4, R1 and R2 conductor resistances per metre, cable length, calculated (R1+R2), external loop impedance Ze, total Zs, temperature correction factor, and pass/fail result.
Why is temperature correction applied to Zs calculations?
Conductor resistance increases with temperature. Design calculations at 20°C must be corrected to the operating temperature of the conductor under fault conditions. BS 7671 uses a factor of 1.20 for thermoplastic (PVC) and 1.28 for thermosetting (XLPE) insulated cables to correct from 20°C to maximum operating temperature.