ABB RELION REX640 Technical Manual page 940

Section 4
Protection functions
934
Table 868: Voltages and currents used in impedance calculation
Measurement mode Phase Sel for Z Clc
1Phase-earth
1Phase-earth
1Phase-earth
1Phase-phase
1Phase-phase
1Phase-phase
3Phase-earth
3Phase-phase
Pos seqn
If all three phase voltages and phase currents are fed to the protection
relay, the positive-sequence alternative is recommended.
If the polarity of the voltage signals is opposite to the normal polarity, the correction
can be done by setting Voltage reversal to "Yes", which rotates the impedance vector
by 180 degrees.
If the magnitude of the voltage is less than 0.05 · U
reliable and the impedance calculation is disabled. U
voltage.
The calculated impedance magnitudes and angles are available in the Monitored data
view. The impedance angles are provided between -180...180 degrees.
The calculated apparent impedance is converted to pu impedance as
the operating characteristics are defined with the pu settings.
Impedance reach check
The operating characteristic is a circular offset mho on the impedance plane. The
operating characteristics are defined with the Offset, Diameter and Displacement
settings. If the calculated impedance value enters the circle in the impedance plane, the
module sends an enabling signal to start the Timer.
Voltages and currents
A or AB U_A, I_A
B or BC U_B, I_B
C or CA U_C, I_C
A or AB U_AB, I_A, I_B
B or BC U_BC, I_B, I_C
C or CA U_CA, I_C, I_A
N/A U_A, U_B, U_C, I_A, I_B, I_C
N/A U_AB, U_BC, U_CA, I_A, I_B, I_C
N/A { U_A,U_B,U_C } or { U_AB,U_BC,U_CA } and
I_A, I_B, I_C
1MRS759142 C
, the calculated impedance is not
N
is the rated phase-to-phase
N
Technical Manual
REX640