Negative Sequence Based - ABB REQ650 Applications Manual

Section 8
Secondary system supervision
8.2.3.3
130
fuse fail when closing the local breaker when the line is already energized from the
other end. When the remote breaker closes the voltage will return except in the
phase that has a persistent fuse fail. Since the local breaker is open there is no
current and the dead phase indication will persist in the phase with the blown fuse.
When the local breaker closes the current will start to flow and the function detects
the fuse failure situation. But due to the 200 ms drop off timer the output BLKZ
will not be activated until after 200 ms. This means that distance functions are not
blocked and due to the "no voltage but current" situation might issue a trip.
The operation mode selector OpMode has been introduced for better adaptation to
system requirements. The mode selector enables selecting interactions between the
negative sequence and zero sequence algorithm. In normal applications, the
OpMode is set to either UNsINs for selecting negative sequence algorithm or
UZsIZs for zero sequence based algorithm. If system studies or field experiences
shows that there is a risk that the fuse failure function will not be activated due to
the system conditions, the dependability of the fuse failure function can be
increased if the OpMode is set to UZsIZs OR UNsINs or OptimZsNs. In mode
UZsIZs OR UNsINs both negative and zero sequence based algorithms are
activated and working in an OR-condition. Also in mode OptimZsNs both negative
and zero sequence algorithms are activated and the one that has the highest
magnitude of measured negative or zero sequence current will operate. If there is a
requirement to increase the security of the fuse failure function OpMode can be
selected to UZsIZs AND UNsINs which gives that both negative and zero sequence
algorithms are activated and working in an AND-condition, that is, both algorithms
must give condition for block in order to activate the output signals BLKU or
BLKZ.

Negative sequence based

The relay setting value 3U2> is given in percentage of the base voltage UBase and
should not be set lower than the value that is calculated according to equation 36.
U 2
 
3 U 2 100
UBase 3
EQUATION1519 V5 EN-US
where:
U2 is the maximal negative sequence voltage during normal operation conditions, plus a margin
of 10...20%
UBase is the base voltage for the function according to the setting GlobalBaseSel
The setting of the current limit 3I2< is in percentage of parameter IBase. The
setting of 3I2< must be higher than the normal unbalance current that might exist
in the system and can be calculated according to equation 37.
1MRK 505 383-UEN A
M13683-17 v9
(Equation 36)
Breaker protection REQ650 2.2 IEC
Application manual