Use this Protection Relay Setting Calculator to calculate pickup current, time multiplier settings (TMS), operating time, coordination time interval (CTI), and plug setting multiplier (PSM) using fault current, CT ratio, and IEC 60255 curve parameters. What is a Time Overcurrent Relay? Inverse Definite Minimum Time (IDMT) relays activate when current exceeds a predetermined pickup value with the. This process ensures that the “Downstream” relay (closest to the fault) trips milliseconds before the “Upstream” relay (closer to the power source) even decides to act. Historically, this required incredibly expensive protection coordination software or tedious manual calculations on logarithmic. Professional protection relay testing calculator implementing IEEE C37. Select from the standard set of IEC and IEEE curves. Why would you use it? By using the calculator, a time for operation can be.
[PDF Version]