IDMT curves for overvoltage protection - Arc protection - Motor protection - Feeder protection - Back-up protection - Technical Manual - REX610 Protection and control - 1.2 - IEC - ANSI - 17.02.2023

REX610 Technical Manual

In inverse-time modes, the operate time depends on the momentary value of the voltage, the higher the voltage, the faster the operate time. The operate time calculation or integration starts immediately when the voltage exceeds the set value of the Start value setting and the START output is activated.

The OPERATE output of the component is activated when the cumulative sum of the integrator calculating the overvoltage situation exceeds the value set by the inverse time mode. The set value depends on the selected curve type and the setting values used. The user determines the curve scaling with the Time multiplier setting.

The Minimum operate time setting defines the minimum operate time for the IDMT mode, that is, it is possible to limit the IDMT based operate time for not becoming too short. For example:
Figure 1. Operate time curve based on IDMT characteristic with Minimum operate time set to 0.5 second
Figure 2. Operate time curve based on IDMT characteristic with Minimum operate time set to 1 second