How does an IDMT relay work?

An IDMT (Inverse Definite Minimum Time) relay is a protective device used in electrical systems to detect overcurrent conditions. It operates on the principle that the time it takes to trip decreases as the level of overcurrent increases, following an inverse time characteristic. When the current exceeds a predetermined threshold, the relay begins timing, and the more the current exceeds this threshold, the shorter the tripping time becomes. This allows for selective tripping of circuits, helping to isolate faults while minimizing disruption to the overall system.