ABB RELION 670 Series Applications Manual page 164

Section 7
Current protection
For ANSI inverse time delay characteristics all three types of reset time characteristics are
available; instantaneous (1), IEC (2 = set constant time reset) and ANSI (3 = current dependent
reset time).
For IEC inverse time delay 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 then 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
tPCrvx , tACrvx , tBCrvx , tCCrvx : Parameters for customer creation of inverse time characteristic
curve (Curve type = 17). See equation
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EQUATION1261 V2 EN-US
For more information, please refer to the "
tPRCrvx , tTRCrvx , tCRCrvx : Parameters for customer creation of inverse reset time characteristic
curve (Reset Curve type = 3). Further description can be found in the "
7.2.3.2 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
prevent this unwanted function.
The settings for the 2
2ndHarmStab : The rate of second harmonic current content for activation of the 2
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
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
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Off/On .
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nd
harmonic component. This component can be used to create a restrain signal to
nd
harmonic restrain are described below.
33 for the time characteristic equation.
Technical reference manual ".
1MRK 505 337-UUS A
(Equation 33)
Technical reference manual ".
SEMOD127941-90 v1
nd
harmonic
nd
harmonic restrain.
Application manual