Protective Relay Settings: ct_class
Protective relay settings and coordination parameters per IEEE C37 and IEEE 242. Covers IEEE C37.112-2018 inverse time-overcurrent curve constants (A, B, p, tr) for moderately/very/extremely inverse curves and SEL vendor extensions; IEC 60255-151 curve constants (k, alpha); CT accuracy classes C100/C200/C400/C800 per IEEE C57.13-2016 with burden limits; relay pickup guidance by ANSI device number (50, 51, 50N, 51N, 27, 59, 81U, 81O); coordination time intervals (CTI) per IEEE 242-2001; and CT saturation voltage thresholds.
| parameter type | record id | curve designation | curve name | curve standard | notes | time dial range max | time dial range min |
|---|---|---|---|---|---|---|---|
| ct_class | C100 | C100 | Class C100 | IEEE C57.13 | Standard relaying burden: 1.0 ohm; terminal voltage: 100V at 20x rated secondary (100A); <10% ratio error; suitable for short relay lead lengths | 8 | 0.5 |
| ct_class | C200 | C200 | Class C200 | IEEE C57.13 | Standard relaying burden: 2.0 ohm; terminal voltage: 200V at 20x rated secondary; <10% ratio error; most common for distribution protection | 8 | 0.5 |
| ct_class | C400 | C400 | Class C400 | IEEE C57.13 | Standard relaying burden: 4.0 ohm; terminal voltage: 400V at 20x rated secondary; <10% ratio error; required for high-impedance differential protection | 8 | 0.5 |
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