The P632 calculates the negative-sequence current from the three phase current values according to this equation. This is based on the setting at MAIN: Phase sequence.

Phase sequence A-B-C:

Phase sequence A-C-B:

The negative-sequence current is monitored by the P632 to detect when it exceeds the set thresholds. Alternatively, two different thresholds can be active. The “dynamic” thresholds are active for the set hold time for the “dynamic parameters” (see Chapter “Activation of “Dynamic Parameters””) and the “normal” thresholds are active when no hold time is running. The IDMT protection will trigger when the 1.05-fold of the set reference current value is exceeded. Dependent on the characteristic selected and the negative-sequence current magnitude the P632 will determine the tripping time. Furthermore, a minimum tripping time can be set; the tripping time will not fall below this minimum independent of the magnitude of the current.

The negative-sequence current stage of the IDMT protection function can optionally be blocked by the inrush stabilization function of differential protection.