ABB RELION REX640 Technical Manual page 713

1MRS759142 C
REX640
Technical Manual
Low operatevalue I
=
d 1
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The Slope section 2 and Slope section 3 settings are determined correspondingly:
I
d
2
Slope section 2 100
= ⋅
I
b
2
GUID-62E58877-B39C-4F26-AE7E-D2DC7F011288 V1 EN
I
d 3
Slope section
3 100
= ⋅
I
b 3
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The end of the first section End section 1 can be set at a desired point within the range
of 0 to 100 percent (or % I
can be set within the range of 100 percent to 300 percent (or % I
The slope of the operating characteristic for the function block varies in different parts
of the range.
In section 1, where 0.0 < I
tripping is constant. The value of the differential current is the same as the Low operate
value setting selected for the function block. The Low operate value setting allows for
small inaccuracies of the current transformers but it can also be used to influence the
overall level of the operating characteristic.
Section 2, where End section 1 < I
the setting Slope section 2. In this section, variations in End section 2 affect the slope
of the characteristic, that is, how big the change in the differential current required for
tripping is in comparison to the change in the load current. The End section 2 setting
allows for CT errors.
In section 3, where I /I
b n
Slope section 3 that defines the increase in the differential current to the corresponding
increase in the biasing current.
The required differential current for tripping at a certain stabilizing current level can
be calculated using the formulae:
For a stabilizing current lower than End section 1
I [% ] = I Set Low operatevalue
doperate r
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For a stabilizing current higher than End section 1 but lower than End section 2
I I Low operatevalue
[% ]
=
doperate r
GUID-2DF3B1E5-426C-4073-A242-53475798327F V1 EN
For higher stabilizing current values exceeding End section 2
I I Low operatevalue
[% ] (
= +
d operate r
GUID-91703E91-F12B-4C7F-8C54-68183D5F68BA V1 EN
%
%
). Accordingly, the end of the second section End section 2
r
/I < End section 1, the differential current required for
b n
/I < End section 2, is called the influence area of
b n
> End section 2, the slope of the characteristic can be set by
I Ir End section
( [% ]
+ −
b
End section End section S l l ope section
2 1 )
− ⋅
Section 4
Protection functions
(Equation 155)
(Equation 156)
(Equation 157)
).
r
(Equation 158)
Slope s s ection 2
1 )
⋅
(Equation 159)
I I End section Slope section
2 ( [% ] 2 )
+ − ⋅
b r
(Equation 160)
3
707