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.
14.2.3.3
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
100
3
2
2
3
UBase
U
U
EQUATION1519 V5 EN
(Equation 261)
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 14
1MRK 502 071-UEN -
Secondary system supervision
474
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual
Содержание Relion REG670
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