The settings of negative sequence, zero sequence and delta algorithm are in percent of the
global base voltage and global base current for the function,
VBase
and
IBase
respectively.
The voltage threshold
VSealInPU
is used to identify low voltage condition in the system.
Set
VSealInPU
below the minimum operating voltage that might occur during emergency
conditions. We propose a setting of approximately 70% of the global parameter
VBase
.
The drop off time of 200 ms for dead phase detection makes it recommended to always set
SealIn
to
Enabled
since this will secure a fuse failure indication at persistent 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
OpModeSel
has been introduced for better adaptation to
system requirements. The mode selector makes it possible to select 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 the negative and zero sequence based
algorithm is activated and working in an OR-condition. Also in mode
OptimZsNs
both the
negative and zero sequence algorithm are activated and the one that has the highest
magnitude of measured 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 algorithm is activated working in an
AND-condition, that is, both algorithms must give condition for block in order to activate
the output signals BLKV or BLKZ.
10.2.3.3
Negative sequence based
The relay setting value
3V2PU
is given in percentage of the base voltage
VBase
and should
not be set lower than according to equation
Section 10
1MRK 506 334-UUS A
Secondary system supervision
278
Application manual
Содержание REL650 series
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