ABB 615 Series - Page 714

Table 613: Voltages and currents used in impedance calculation
Impedance Meas mode Phase Sel for Z Clc Voltages and currents used in
impedance calculation
1)
1Phase-phase AB
ZAB
V AB
I A I B
=
−
_
_ _
1Phase-phase BC
ZBC
V BC
I B I C
=
−
_
_ _
1Phase-phase CA
ZCA
V CA
I C I A
=
−
_
_ _
3Phase-phase N/A
ZAB
V AB
I A I B
=
−
_
_ _
ZBC
V BC
I B I C
=
−
_
_ _
ZCA
V CA
I C I A
=
−
_
_ _
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
N
, where I
N
is the nominal phase current, the
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.
Section 4 1MAC059074-MB A
Protection functions
708 615 series ANSI
Technical Manual