ABB RELION 670 Series Technical Manual page 252

Section 7
Impedance protection
where:
maxIph
INRelPG
IBase
In systems where the source impedance for zero sequence is high the change of zero sequence
current may not be significant and the above detection may fail. In those cases the detection
enters the second level, with evaluation of zero and negative sequence voltage. The release of the
ground-fault loops can then be achieved if all of the following conditions are fulfilled:
|3V |>|V
0 2
|3V |>V
0 1
|V |> VBase × 0.2/√(3)
1
and
3I <0.1 × IBase
0
or
3I <maxIph ×
0
where:
3V
0
V
2
k5
ILmax
IMinOp
Phase-to-phase fault detection
The detection of phase-to-phase fault is performed by evaluation of the angle difference between
the sequence voltages V
246
is the maximal current magnitude found in any of the three phases
is the setting of 3I0 limit for release of phase-to-ground measuring loop in % of
IBase
is the global setting of the base current (A)
| × 0.5
| × 0.2
INRelPG
is the magnitude of the zero sequence voltage
is the magnitude of the negative sequence voltage at the relay measuring point
is design parameter
is the maximal phase current
is the setting of minimum operate phase current in % of
and V
2 1
.
1MRK 502 066-UUS B
IBase
Technical manual
SEMOD153832-119 v2