ABB RELION 620 Series Technical Manual page 415

1MAC504801-IB E
620 series ANSI
Technical Manual
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
n
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
is constant. The value of the differential current is the same as the Low trip value setting
selected for the function block. The Low trip 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
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 is 100 percent, which means that an increase in the differential current is equal to the
corresponding increase in the stabilizing 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 [% ] = Set I Low trip values
doperate n
GUID-4FAC8F94-FBB0-47DB-A952-F995889969C6-ANSI V1 EN
For a stabilizing current higher than End section 1 but lower than End section 2
I [% ] I = Low trip value
doperate n
GUID-EB0A327A-4079-45A5-87E6-AA30A8D2220C-ANSI V1 EN
For higher stabilizing current values exceeding End section 2
I [% ] I = Low trip value
doperate n
GUID-E9DA330C-84A8-40C2-BCFB-1F7E517395D8-ANSI V1 EN
When the differential current exceeds the operating value determined by the operating
characteristics, the OPR_LS output is activated. The TRIP output is always activated
when the OPR_LS output activates.
The trip 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
). Accordingly, the end of the second section End section 2 can
/I < End section 1, the differential current required for tripping
b n
/I < End section 2, is called the influence area of the
b n
> End section 2, the slope of the characteristic is constant. The
+ ( [% ] I I − End section 1 Slop
b n
+ ( End section 2 − End section 1) )
Protection functions
).
n
) ⋅ e e section 2
⋅ Slope section 2 + ( [% ] I I − End section
b n
Section 4
(Equation 36)
(Equation 37)
2 )
(Equation 38)
409