The function calculates the positive sequence impedance. Calculation is based on
fundamental frequency components of positive sequence current and voltage. If
the measured impedance stays between inner and outer characteristic longer than
predetermined time and moves farther inside the inner characteristic, then a power
swing condition is indicated.
4.7.6.4 Analog channel configuration
DSTRPSB has two analog group inputs which must be properly configured.
Table 980: Analog Inputs
Input Description
I3P Three-phase currents
U3P Three-phase voltages
There are a few special conditions which must be noted with the configuration.
Table 981: Special conditions
Condition Description
U3P connected to real measurements The function can work with any two voltage
channels connected but it is recommended
to connect all three voltage channels.
4.7.6.5 Operation principle
The
Operation
setting is used to enable or disable the function. When selected "On"
the function is enabled and respectively "Off" means function is disabled.
The operation of DSTRPSB can be described by using a module diagram (see figure
below). All the modules in the diagram are explained in the next sections.
BLOCK
PSB
Power
swing
detection
Impedance
calculation
I
2
U
1
SWING_ST
U3P
I3P
I
1
Figure 584: Function module diagram
Impedance calculation
This module receives positive sequence voltage which is calculated from
fundamental frequency three phase voltages and positive sequence current
calculated respectively from fundamental frequency three phase currents. For the
module to calculate impedance it is required that the positive-sequence current is
above 0.1xIn.
Operation is based on positive sequence impedance (Z
1
) which is calculated using
positive sequence voltage and current as follows:
1MRS759142 F
Protection functions
REX640
Technical Manual
1047
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