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Field Testing & Twin SaaS
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#04MV/HV Protection Relay Setting Calculator

Project Framework (report reference): IEC 60364-4-41Applicable Standard: IEC 60255 / IEEE C37
Module Field Guides, Standard Selection & Tutorials (3)Browse All 93+ Guides →
1 · Field Measurement ProcedureHow to Measure & Test Protection Relay Settings on Site: Step-by-Step Field Procedure (IEC 60255 / IEEE C37)2 · Standards & Limit TablesWhich Standard Applies to Protection Relay Settings? Acceptance Limits, Annex Tables & Regional Equivalents (IEC 60255 / IEEE C37)3 · OhmCert Tutorial & Case StudyHow to Complete a Protection Relay Settings Certificate in OhmCert: Worked Case Study & Troubleshooting

Multi-Asset / Multi-Point Equipment Schedule

Inspect multiple transformers, panels, rooms, motors, or RCDs in this module without overwriting previous assets. Each item receives a permanent QR Sticker UID preserved across annual audits.

Sticker UID: OC-RELA-3B08
Plant & SLD (Auto-SLD)

Standard Limits, Equations & Space Presets

IEC 60255-151 and IEEE C37.112 IDMT overcurrent relay curve constants, operating time equations, and numerical vs electromechanical grading margins.

One-Click Normative Presets (Auto-fills Target Limits)

Measured Inputs

Calculated / Evaluated Results

IEC 60255-151 & IEEE C37.112 characteristic: t = ((k / (M^a - 1)) + c) x TMS with M = If / Is. Grading against the downstream device uses the 0.30 s discrimination margin. Requires explicit TMS input (never assumed).

Pending / Not tested — results stay neutral until valid measured values are entered.

  • Multiple of Pickup M = If / Is

    -

    The element only operates on the inverse characteristic when M > 1.0.

    Pending

  • Operating Time t

    -

    Not tested - enter the measured value. Acceptance: Standard Inverse (IEC 60255-151): k = 0.14, a = 0.02 [IEC 60255-151]

    Pending

  • Grading Margin vs Downstream Device

    - s

    Not tested - enter the measured value. Acceptance: Discrimination margin >= 0.30 s over the downstream device [IEC 60255 / IEEE C37.112 field practice]

    Pending

Verification Checklist (0 / 13)

Pending

  • 1Relay model, serial number, firmware revision, and active setting group verified against approved protection coordination study [IEC 60255]

  • 2Current Transformer (CT) ratio, accuracy limit factor (5P10 / 5P20), knee-point voltage, and star-point polarity proven by injection

  • 3Voltage Transformer (VT) ratio, secondary MCB/fuse supervision, and phase rotation verified

  • 4CT shorting links and test block isolation verified safe prior to secondary injection kit connection

  • 5Phase overcurrent pickup (51 Ip) and instantaneous/high-set (50 I>>) trip thresholds verified within +/-2.5% tolerance

  • 6IDMT curve timing (IEC SI / VI / EI or IEEE MI / VI / EI) tested at 2x, 5x, and 10x Ip against theoretical curve [IEC 60255-151]

  • 7Earth fault / residual overcurrent (50N/51N or 51G) pickup and time delay proven across full grading range

  • 8Upstream-to-downstream selectivity Grading Margin (>= 0.25-0.30 s for numerical relays) verified at maximum fault level

  • 9Trip circuit supervision (TCS / ANSI 74) and actual circuit breaker trip coil mechanical opening proven from relay output contacts

  • 10Breaker Failure (50BF) re-trip and upstream inter-trip timer logic verified

  • 11Disturbance / fault waveform recorder (COMTRADE) and NTP/IRIG-B time synchronisation verified operational

  • 12SCADA / IEC 61850 GOOSE / Modbus trip and alarm telemetry confirmed end-to-end with control room

  • 13Test block restored to normal service, secondary CT links sealed, and protection setting sheet signed off

General Notes

PDF Certificate Language:

Free plan: 5 of 5 inspections / calculations left this month.