2Nd Harmonic Restrain - ABB Relion REC670 Applications Manual

Section 7
Current protection
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=
t s
EQUATION1261 V2 EN-US
tPRCrvx , tTRCrvx , tCRCrvx : These parameters are used by the customer to create the inverse
reset time characteristic curve. For more information, refer to
HarmRestrainx : Enables the block of step x from the harmonic restrain function (2nd
harmonic). This function should be used when there is a risk of an unwanted trip caused by
power transformer inrush currents. It can be set to
7.2.3.2

2nd 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
restrain signal to prevent this unwanted function.
The settings for the 2nd harmonic restrain are described below.
2ndHarmStab : The rate of 2nd harmonic current content for activation of the 2nd harmonic
restrain signal, to block chosen steps. The setting is given in % of the fundamental frequency
residual current. The setting range is
can be used if a deeper investigation shows that no other value is needed..
HarmRestrainx : This parameter can be set Off / On , to disable or enable the 2nd harmonic
restrain.
The four step phase overcurrent protection 3-phase output can be used in different ways,
depending on the application where the protection is used. A general description is given
below.
The operating current setting of the inverse time protection, or the lowest current step of the
definite time protection, must be defined 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 45.
110
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B IxMult
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nd
harmonic component. This component can be used to create a
Off / On .
5 - 100 % in steps of 1%. The default setting is 20% and
1MRK 511 358-UEN A
(Equation 28)
Technical manual .
Application manual
M12982-91 v8