Areva MiCOM P921 - Page 109

Technical Guide P92x/EN FT/E11
User Guide
MiCOM P921-P922-P923 Page 31/110
8.1.3 "2Vpp+Vr" configuration (2 “Phase-Phase” VTs + 1 residual VT)
The 2 line voltages Vab, Vbc and the residual voltage Vr are then measured by the
MiCOM relay.
The derived quantities are : positive and negative sequences voltages (V1 and V2,
only for MiCOM P922 and p923), and the Vca line voltage.
)VBC
)a21(
)1a(
VAB(3/11V
+
-
+-=
with a = e
j2
p
/3
)VBC
)a21(
)a2(
VAB(3/12V
+
+
+-=
)VBCVAB(VCA +-=
The only protection mode, which is available in this configuration, is the "Phase-
Phase" mode.
8.1.4 "3Vpn+Vr" configuration (3 "Phase-Neutral" VTs + 1 residual VT)
The 3 phase voltages VA, VB, VC and the residual voltage Vr will be measured by the
MiCOM relay.
The derived quantities are : positive and negative sequences voltages (V1 and V2,
only for MiCOM P922 and p923).
)VC²aVBaVA(3/11V ++= with a = e
j2
p
/3
)VCaVB²aVA(3/12V ++=
If the protection mode is “Phase-Phase”, the line voltages Vab, Vbc and Vca will be
used in the protection algorithms. These line voltages are derived from the formulas
below :
)VAVB(VAB -=
)VBVC(VBC -=
)VCVA(VCA -=
Please refer to the chapter P92x/EN CO of this Technical Guide, in which all the
connection schemes are indicated.