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 OpModeSel
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
OpModeSel is set to either V2I2 for selecting negative sequence algorithm or V0I0 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 OpModeSel is set
to V0I0 OR V2I2 or OptimZsNs. In mode V0I0 OR V2I2 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
OpModeSel can be selected to V0I0 AND V2I2 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 BLKV
or BLKZ.
11.1.3.3 Negative sequence based
M13683-17 v9
The relay setting value 3V2PU is given in percentage of the base voltage VBase and
should not be set lower than the value that is calculated according to equation
82.
EQUATION1757-ANSI V4 EN-US (Equation 82)
where:
V2PU is the maximal negative sequence voltage during normal operation conditions, plus a margin of
10...20%
VBase
is the base voltage for the function according to the setting
GlobalBaseSel
The setting of the current limit 3I2PU is in percentage of parameter IBase. The setting
of 3I2PU must be higher than the normal unbalance current that might exist in the
system and can be calculated according to equation 83.
1MRK 505 370-UUS A Section 11
Secondary system supervision
Busbar protection REB670 2.2 ANSI 287
Application manual
To Next Page
Loading...
