ABB 615 series Technical Manual page 714

Section 4
Protection functions
708
Table 613: 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.
If all three phase or phase-phase voltages and phase currents are fed to the
protection relay, the "3Phase-phase" mode is recommended.
The current measurement of the function is based on two alternative measurement modes,
"DFT" and "Peak-To-Peak". The measurement mode is selected using the Measurement
mode setting.
If the current magnitude is below 0.02 · I
impedance value is not evaluated and the maximum impedance value (99.999 pu) is
shown in the Monitored data view.
The calculated impedances are converted to a pu impedance as the
operating characteristics are defined using the Polar reach setting in %Zb.
The calculated phase-phase impedance amplitudes ZAB_AMPL, ZBC_AMPL and
ZCA_AMPL are available as pu values in the Monitored data view.
Phase Sel for Z Clc
AB
BC
CA
N/A
, where I is the nominal phase current, the
N N
1MAC059074-MB A
Voltages and currents used in
1)
impedance calculation
V AB
_
ZAB
=
I A I B _ _
−
V BC _
ZBC
=
I B I C _ _
−
V CA _
ZCA
=
I C I A
_ _
−
V _ AB
ZAB
=
I A I B
_ _
−
V BC _
ZBC
=
I B I C _ _
−
V CA
_
ZCA
=
I C I A _ _
−
615 series ANSI
Technical Manual