Monitored Data; Operation Principle - ABB REG650 Technical Manual

Section 8
Current protection
8.9.6
8.9.7
246

Monitored data

Table 145: NS2PTOC Monitored data
Name Type
NSCURR REAL

Operation principle

The negative sequence time overcurrent protection for machines (NS2PTOC)
function directly measures the amplitude of the negative phase sequence component
of the measured current. NS2PTOC sets the START, ST1 or ST2 outputs active and
starts to count trip time only when the measured negative sequence current value rises
above the set value of parameters I2-1> or I2-2> respectively.
To avoid oscillation in the output signals, a certain hysteresis has been included. For
both steps, the reset ratio is 0.97.
Step 1 of NS2PTOC can operate in the Definite Time (DT) or Inverse Time (IDMT)
mode depending on the selected value for the CurveType1 parameter. If CurveType1=
Definite, NS2PTOC operates with a Definite Time Delay characteristic and if
CurveType1 = Inverse, NS2PTOC 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 start 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 has already started but not tripped and measured negative
sequence current drops below the start value, the start outputs remains active for the
time defined by the resetting parameters.
A BLOCK input signal resets NS2PTOC momentarily.
When the parameter CurveType1 is set to Inverse, an inverse curve is selected
according to selected value for parameter K1. 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 K1, which must be set according to the
generators negative sequence current capacity.
=
K I t
2
2
EQUATION2112 V1 EN
Values (Range) Unit
- A
1MRK 502 048-UEN A
Description
Negative sequence
current in primary amps
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