ABB RELION 670 Series Applications Manual page 156

Section 7
Current protection
The delay characteristics are described in
the choice of the reset delay.
For the definite time delay characteristics, the possible delay time setting instantaneous (1) and
IEC (2 = set constant time reset).
For ANSI inverse time 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 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
be given.
tResetx : Constant reset time delay in seconds for step x.
tPCrvx , tACrvx , tBCrvx , tCCrvx : These parameters are used by the customer to create the inverse
time characteristic curve. See equation
information, refer to
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ANSI-EQUATION1261 V1 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
7.1.3.2 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
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
be used if a deeper investigation shows that no other value is needed..
150
Technical manual .
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nd
harmonic component. This component can be used to create a restrain signal to
Technical manual . There are some restrictions regarding
27 for the time characteristic equation. For more
Technical manual .
Disabled / Enabled .
5 - 100 % in steps of 1%. The default setting is 20% and can
1MRK 505 337-UUS A
pr , tr and cr must
(Equation 27)
M12982-91 v8
Application manual