ABB REB670 - Second Harmonic Restrain

HarmRestrainx: Enable block of step x from the harmonic restrain function (2nd
harmonic). This function should be used when there is a risk if power transformer
inrush currents might cause unwanted trip. Can be set Off/On.
tPCrvx, tACrvx, tBCrvx, tCCrvx: Parameters for customer creation of inverse time
characteristic curve (Curve type = 17). See equation 30 for the time characteristic
equation.
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EQUATION1261 V2 EN-US (Equation 30)
For more information, please refer to the “Technical r
eference manual”.
tPRCrvx, tTRCrvx, tCRCrvx: Parameters for customer creation of inverse reset time
characteristic curve (Reset Curve type = 3). Further description can be found in the
“Technical reference manual”.
7.2.3.2 Second harmonic restrain
SEMOD127941-90 v1
If a power transformer is energized there is a risk that the transformer core will saturate
during part of the period, resulting in an inrush transformer current. This will give a
declining residual current in the network, as the inrush current is deviating between the
phases. There is a risk that the phase overcurrent function will give an unwanted trip.
The inrush current has a relatively large ratio of 2
nd
harmonic component. This
component can be used to create a restrain signal to prevent this unwanted function.
The settings for the 2
nd
harmonic restrain are described below.
2ndHarmStab: The rate of second harmonic current content for activation of the 2
nd
harmonic restrain signal, to block chosen steps. The setting is given in % of the
fundamental frequency residual current. The setting range is 5-100% in step of 1%.
The default setting is 20%.
HarmRestrainx: This parameter can be set Off/On, disable or enable the 2
nd
harmonic
restrain.
The four-step phase overcurrent protection can be used in different ways, depending on
the application where the protection is used. A general description is given below.
The pick up current setting inverse time protection or the lowest current step constant
inverse time protection must be given a current setting so that the highest possible load
1MRK 505 370-UUS A Section 7
Current protection
Busbar protection REB670 2.2 ANSI 191
Application manual