parameter the operation time of the step can never be shorter than the setting. Settingrange: 0.000 - 60.000s in steps of 0.001s.IEC09000164-2Operate timeCurrenttxtnMinIMinnIEC09000164 V2 ENFigure 36: Minimum operate current and operation time for inverse timecharacteristicsIn order to fully comply with curves definition setting parameter tnMin shall be set to thevalue, which is equal to the operating time of the selected inverse curve for measuredcurrent of twenty times the set current pickup value. Note that the operating time value isdependent on the selected setting value for time multiplier TDn.HarmRestrainx: Enable block of step n from the harmonic restrain function (2ndharmonic). This function should be used when there is a risk if power transformer inrushcurrents might cause unwanted trip. Can be set Disabled/Enabled.6.2.3.2 2nd harmonic restrainIf a power transformer is energized there is a risk that the transformer core will saturateduring part of the period, resulting in an inrush transformer current. This will give adeclining residual current in the network, as the inrush current is deviating between thephases. There is a risk that the phase overcurrent function will give an unwanted trip. Theinrush current has a relatively large ratio of 2nd harmonic component. This component canbe used to create a restrain signal to prevent this unwanted function.The settings for the 2nd harmonic restrain are described below.Section 6 1MRK 511 286-UUS ACurrent protection96Application manual
