ABB RELION 620 Series Technical Manual page 500

Section 4
Protection functions
494
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 Lowoperate value
doperate r
GUID-4FAC8F94-FBB0-47DB-A952-F995889969C6 V2 EN
For a stabilizing current higher than End section 1 but lower than End section 2
I [% ] I Lowoperate value
=
doperate r
GUID-EB0A327A-4079-45A5-87E6-AA30A8D2220C V2 EN
For higher stabilizing current values exceeding End section 2
I [% ] I Lowoperate value
= +
d operate r
GUID-E9DA330C-84A8-40C2-BCFB-1F7E517395D8 V3 EN
When the differential current exceeds the operating value determined by the operating
characteristics, the OPR_LS output is activated. The OPERATE output is always
activated when the OPR_LS output activates.
The operate signal due to the biased stage can be blocked by the activation of the
BLK_OPR_LS or BLOCK input. Also, when the operation of the biased low stage is
blocked by the waveform blocking functionality, the INT_BLKD output is activated
according to the phase information.
). 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 2 End section 1 ) S l l ope section
− ⋅
1MRS757644 F
).
r
(Equation 62)
1 ) Slope s s ection 2
⋅
(Equation 63)
2 ( [% ] I I End section 2 ) Slope section
+ − ⋅
b r
(Equation 64)
620 series
Technical Manual
3