motor. Therefore there is a possibility to give a setting of a multiplication factor to the currentpick-up level. This multiplication factor is activated from a binary input signal to the function.Power transformers can have a large inrush current, when being energized. This phenomenon isdue to saturation of the transformer magnetic core during parts of the period. There is a risk thatinrush current will reach levels above the pick-up current of the phase overcurrent protection. Theinrush current has a large 2nd harmonic content. This can be used to avoid unwanted operation ofthe protection. Therefore, OC4PTOC (51/67) have a possibility of 2nd harmonic restrain if the levelof this harmonic current reaches a value above a set percentage of the fundamental current.The phase overcurrent protection is often used as protection for two and three phase shortcircuits. In some cases it is not wanted to detect single-phase ground faults by the phaseovercurrent protection. This fault type is detected and cleared after operation of ground faultprotection. Therefore it is possible to make a choice how many phases, at minimum, that have tohave current above the pick-up level, to enable operation. If set1 of 3 it is sufficient to have highcurrent in one phase only. If set2 of 3 or3 of 3 single-phase ground faults are not detected.7.2.3 Setting guidelines IP14982-1 v1M12982-4 v14When inverse time overcurrent characteristic is selected, the trip time of the stagewill be the sum of the inverse time delay and the set definite time delay. Thus, ifonly the inverse time delay is required, it is important to set the definite time delayfor that stage to zero.The parameters for the directional phase overcurrent protection, four steps OC4PTOC (51/67) areset via the local HMI or PCM600.The following settings can be done for OC4PTOC (51/67).GlobalBaseSel: Selects the global base value group used by the function to define (IBase), (VBase)and (SBase).MeasType: Selection of discrete Fourier filtered (DFT) or true RMS filtered (RMS) signals.RMS isused when the harmonic contents are to be considered, for example in applications with shuntcapacitors.Operation: The protection can be set toEnabled orDisabled.AngleRCA: Protection characteristic angle set in degrees. If the angle of the fault loop current hasthe angle RCA, the direction to the fault is forward.AngleROA: Angle value, given in degrees, to define the angle sector of the directional function,shown in Figure 55.NumPhSel: Number of phases, with high current, required for operation. The setting possibilitiesare:1 out of 3,2 out of 3 and3 out of 3. The default setting is1 out of 3.PUMinOpPhSel: Minimum current setting level for releasing the directional start signals in % ofIB.This setting should be less than the lowest step setting. The default setting is 7% ofIB.2ndHarmStab: Operate level of 2nd harmonic current restrain set in % of the fundamental current.The setting range is5 - 100% in steps of 1%. The default setting is 20%.1MRK 511 358-UUS A Section 7Current protection125Application manual
