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
equation.
[ ]
>
p
A
t s
B
IxMult
i
C
in
=
+
×
-
æ
ö
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.
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
1MRK 505 370-UUS A
Section 7
Current protection
Busbar protection REB670 2.2 ANSI
191
Application manual
Содержание RELION REB670
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