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.
13.2.3.3
Negative sequence based
M13683-17 v9
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
100
3
2
2
3
UBase
U
U
EQUATION1519 V5 EN-US
(Equation 96)
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
Section 13
1MRK 511 407-UEN C
Secondary system supervision
214
Phasor measurement unit RES670 2.2 IEC
Application manual
Summary of Contents for Relion RES670
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