IDMT Relay Operating Time (IEC 60255)
Time to trip for an inverse-time overcurrent relay following IEC 60255 normal/very/extremely inverse curves.
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Formula, assumptions, and limits
| Symbol | Meaning | Unit |
|---|---|---|
| Actual fault current | A | |
| Pickup current | A | |
| Curve constants | ||
| Time multiplier setting | ||
| Operating time | s |
Source: IEC 60255-151 - Measuring relays and protection equipment
In short
Time to trip for an inverse-time overcurrent relay following IEC 60255 normal/very/extremely inverse curves.