This practical guide shows you how to complete a signed, QR-verified MV/HV Protection Relay Setting Calculator certificate in OhmCert Module #04 and how to troubleshoot non-compliant readings on site.
1. Step-by-Step OhmCert UI Workflow
- Open Module #04: Navigate to MV/HV Protection Relay Setting Calculator from the Dashboard.
- Load a 1-Click Standard Annex Preset: Open the blue Standard Annex banner at the top and click a preset (such as "IEC Standard Inverse Feeder (Is=400A, TMS=0.20, If=2400A)") to populate target limits automatically.
- Enter Your Field Measurements: Fill in the measured inputs (Fault Current If, Overcurrent Pickup Setting Is, Time Multiplier Setting TMS, IEC 60255 / IEEE C37.112 Curve Type, Downstream Device Operating Time). Blank inputs stay neutral
PENDING. - Complete the 13-Point Checklist: Grade each item, attach photos if needed, and export the SHA-256 signed PDF certificate.
2. Worked Numerical Field Case Study
Scenario: IEC Standard Inverse Feeder (Is=400A, TMS=0.20, If=2400A) (IEC 60255 SI) — Typical 11 kV / 34.5 kV outgoing feeder IDMT setting at 6x fault multiple..
- IEC 60255 / IEEE C37.112 Curve Type:
IEC Standard Inverse (SI) - is:
400 - Time Multiplier Setting TMS:
0.20 - if:
2400 - texp:
0.77 - tup:
1.10
3. Engineering Troubleshooting: Corrective Actions When a Reading Fails
- Increase the upstream relay TMS or switch to a steeper IDMT curve (Very Inverse / Extremely Inverse) to achieve >= 0.30 s grading margin.
- Enable Zone Selective Interlocking (ZSI) or IEC 61850 GOOSE reverse-blocking between main and feeder relays to reduce clearing time without losing selectivity.
- Correct CT ratio or tap settings if relay fault current multiple M = I_fault / I_p exceeds the 20x definite-time saturation knee.
→ Try This Worked Example Live in Module #04 (Protection Relay Settings)