2Nd Harmonic Restrain - ABB REB670 Applications Manual

Section 7
Current protection
7.1.3.2
168
For IEC inverse time characteristics the possible delay time settings are instantaneous (1)
and IEC (2 = set constant time reset).
For the customer tailor made inverse time delay characteristics (type 17) all three types of
reset time characteristics are available; instantaneous (1), IEC (2 = set constant time reset)
and ANSI (3 = current dependent reset time). If the current dependent type is used settings
pr, tr and cr must be given.
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 Disabled/Enabled.
tPCrvx, tACrvx, tBCrvx, tCCrvx: Parameters for customer creation of inverse time
characteristic curve. See equation
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ANSI-EQUATION1261 V1 EN
Further description can be found in the Technical Reference Manual
tPRCrvx, tTRCrvx, tCRCrvx: Parameters for customer creation of inverse reset time
characteristic curve. Further description can be found in the Technical Reference Manual.

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
be used to create a 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 5 - 100% in steps of 1%. The
default setting is 20% and can be used if a deeper investigation shows that no other value
is needed..
27 for the time characteristic equation.
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harmonic component. This component can
1MRK 505 337-UUS -
(Equation 27)
Application manual