ABB RELION REX640 Technical Manual page 1028

Protection functions
Figure 570: Functional module diagram
Impedance calculation
This module calculates the impedance based on the selected voltages and currents.
The
voltages and currents are to be used. If
phase", the
voltages ("AB", "BC" and "CA") and currents should be used for calculating the
impedance.
Table 960: Voltages and currents used in impedance calculation
Impedance Meas mode
1Phase-phase
1Phase-phase
1Phase-phase
3Phase-phase
1
Voltages and currents in the calculations are given in volts and amps.
1028
I_A
I_B
I3P
I_C
U_A_AB
U_B_BC
U3P
U_C_CA
BLOCK
Impedance Meas mode and Phase Sel for Z Clc settings determine which
Phase Sel for Z Clc setting is needed for determining which phase-phase
If all three phase or phase-phase voltages and phase currents are fed to
the protection relay, the "3Phase-phase" mode is recommended.
Under
Impedance
impedance
calculation
detection
Blocking
logic
Impedance Meas mode is set to "1Phase-
Phase Sel for Z Clc
AB
BC
CA
N/A
1MRS759142 F
Timer
OPERATE
t
START
Voltages and currents used
in impedance calculation
U _ AB
=
ZAB
−
I A I B
_ _
U BC
_
=
ZBC
−
I B I C
_ _
U CA _
=
ZCA
I C I A −
_ _
U AB
_
=
ZAB
I A I B −
_ _
U BC
_
=
ZBC
I B I C −
_ _
U CA
_
=
ZCA
−
I C I A _ _
REX640
Technical Manual
1