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CurveType
1 =
Inverse
, NS2PTOC (46I2) operates with an Inverse Time Delay
characteristic. Step 2 can only operate in the Definite Time (DT) mode. The characteristic
defines the time period between the moment when measured negative sequence current
exceeds the set pickup levels in parameter
I2-1>
or
I2-2>
until the trip signal is initiated.
Definite time delay is not dependent on the magnitude of measured negative sequence
current. Once the measured negative sequence current exceeds the set level, the settable
definite timer
t1
or
t2
respectively, starts to count and the corresponding trip signal gets
activated after the pre-set definite time delay has elapsed. Reset time in definite time mode
is determined by the setting parameters
tResetDef1
or
tResetDef2
respectively. If
NS2PTOC (46I2) has already picked up but not tripped and measured negative sequence
current goes below the pickup value, the pickup outputs remains active for the time
defined by the resetting parameters.
A BLOCK input signal resets NS2PTOC (46I2) momentarily.
When the parameter
CurveType
1 is set to
Inverse
, an inverse curve is selected according
to selected value for parameter
K
1. The minimum trip time setting of parameter
t1Min
and
reset time parameter
ResetMultip1
also influence step operation. However, to match the
heating characteristics of the generator, the reset time is depending on the setting of
parameter
K
1, which must be set according to the generators negative sequence current
capacity.
2
2
K
I t
=
EQUATION2112 V1 EN
Where:
I
2
is negative sequence current expressed in per unit of the rated generator current
t
is operating time in seconds
K
is a constant [s], which depends on generator size and design
1MRK 502 048-UUS A
Section 8
Current protection
269
Technical manual
Содержание 650 series
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