Second Harmonic Restrain - ABB REB670 Applications Manual

Section 7
Current protection
7.2.3.2
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EQUATION1261 V2 EN
For more information, please refer to the "Technical reference 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".

Second harmonic restrain

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
be used to create a restrain signal to prevent this unwanted function.
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The settings for the 2 harmonic restrain are described below.
2ndHarmStab: The rate of second harmonic current content for activation of the 2
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
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
current does not cause protection operation. Here consideration also has to be taken to the
protection reset current, so that a short peak of overcurrent does not cause operation of the
protection even when the overcurrent has ceased. This phenomenon is described in
figure 82.
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harmonic component. This component can
1MRK 505 337-UUS -
(Equation 33)
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harmonic
Application manual