ABB REB670 Series - Second harmonic restrain

The delay characteristics are described in the “ Technical reference manual ”. There are some
restrictions regarding the choice of reset delay.
For the independent time delay characteristics the possible delay time settings are
instantaneous (1) and IEC (2 = set constant time reset).
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 Off/On .
tPCrvx , tACrvx , tBCrvx , tCCrvx : Parameters for customer creation of inverse time characteristic
curve (Curve type = 17). See equation 30 for the time characteristic equation.
[ ]
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p
A
t s B IxMult
i
C
in
= + ×
-
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ç ÷
ç ÷
ç ÷
æ ö
ç ÷
ç ÷
è ø
è ø
EQUATION1261 V2 EN-US (Equation 30)
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 ”.
7.2.3.2 Second harmonic restrain
SEMOD127941-90 v1
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
nd
harmonic component. This component can be used to create a
restrain signal to prevent this unwanted function.
The settings for the 2
nd
harmonic restrain are described below.
2ndHarmStab : The rate of second harmonic current content for activation of the 2
nd
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
nd
harmonic 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.
1MRK 505 370-UEN D Section 7
Current protection
Busbar protection REB670 155
Application manual