ABB REL650 series, Applications Manual

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tnMin : Minimum operate time for all inverse time characteristics. At high currents the
inverse time characteristic might give a very short operation time. By setting this
parameter the operation time of the step can never be shorter than the setting.
IEC09000164-2
Operate time
Current
tx
tnMin
IMinn
IEC09000164 V2 EN
Figure 92: Minimum operating current and operation time for inverse time
characteristics
In order to fully comply with curves definition setting parameter tnMin shall be set to the
value which is equal to the operate time of the selected inverse curve for measured current
of twenty times the set current pickup value. Note that the operating time value is
dependent on the selected setting value for time multiplier
TDn .
7.4.3.2 2nd harmonic restrain
2ndHarmStab : Operate level of 2nd harmonic current restrain set in % of the fundamental
current. The setting range is 5-100% in steps of 1%. Default setting is 20%.
HarmRestrainx : Enable block of step x from the harmonic restrain function (2nd
harmonic). This function should be used when there is a risk that power transformer inrush
currents might cause unwanted trip. Can be set
Disabled or Enabled .
OC4SPTOC (51_67) function can be used in different ways, depending on the application
where the protection is used. A general description is given below.
Section 7
1MRK 506 334-UUS A
Current protection
194
Application manual