ABB Relion 670 series, Technical Reference Manual

Page: 300 / 1232

The phase-to-phase loop for the faulty phases will be determined if the angle between
the sequence voltages V
2
and V
1
lies within the sector defined according to figure 149
and the following conditions are fulfilled:
|V
1
|> V1MinOP
|V
2
|> V2MinOp
where:
V1MinOP and V2MinOp
are the setting parameters for positive sequence and negative sequence
minimum operate voltages
The positive sequence voltage V
1
A in figure 149 above is reference.
If there is a three-phase fault, there will not be any release of the individual phase
signals, even if the general conditions for V
2
and V
1
are fulfilled.
Phase-to-ground and phase-to-phase-to-ground-fault detection
The detection of phase-to-ground and phase-to-phase-to-ground fault (US patent
5390067) is based on two conditions:
1. Angle relationship between V
2
and I
0
2. Angle relationship between V
2
and V
1
The condition 1 determines faulty phase at single phase-to-ground fault by determine
the angle between V
2
and I
0
.
Section 6
1MRK505222-UUS C
Impedance protection
294
Technical reference manual