This tool provides a conceptual framework for protective relay coordination. You can input system parameters, configure overcurrent relays, and visualize their time-current characteristics (TCC) for coordination assessment. An organized time-current study of protective devices from the utility to a device. Learn more as we cover basics of power system protection, TCCs for the solid state and thermal magnetic trip, importance, procedure and rules of selective. Discrimination, also called selectivity, is the coordination between series-connected protective devices so that only the device nearest the fault operates, leaving upstream circuits unaffected. IEC 60947-2 Annex A defines methods for verifying full and partial discrimination using time-current. This is known as a “cascading failure” or “sympathetic tripping,” and it is the nightmare scenario every protection engineer strives to avoid.
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