ABB Relion 670 series - Measuring Principles; Minimum Operating Current

IEC05000182-2-en.vsdx
R
X
R
X
R
X
Non-directional Forward Reverse
IEC05000182 V2 EN-US
Figure 75: Directional operating modes of the distance measuring zones
7.1.7.3 Minimum operating current
M16923-127 v5
The operation of Distance measuring zones, quadrilateral characteristic (ZMQPDIS,21) is blocked if
the magnitude of input currents fall below certain threshold values.
The phase-to-ground loop AG (BG or CG) is blocked if IA (IB or IC) <
IMinPUPG .
For zone 1 with load compensation feature the additional criterion applies, that all phase-to-
ground loops will be blocked when IN <
IMinOpIR , regardless of the phase currents.
IA (IB or IC) is the RMS value of the current in phase IA (IB or IC). IN is the RMS value of the vector
sum of the three-phase currents, that is, residual current 3I
0
.
The phase-to-phase loop AB (BC or CA) is blocked if I
AB (BC or CA)
<
IMinPUPP .
All three current limits
IMinPUPG , IMinOpIR and IMinPUPP are automatically
reduced to 75% of regular set values if the zone is set to operate in reverse
direction, that is, OperationDir = Reverse .
7.1.7.4 Measuring principles
M16923-4 v7
Fault loop equations use the complex values of voltage, current, and changes in the current.
Apparent impedances are calculated and compared with the set limits. The apparent impedances
at phase-to-phase faults follow equation
35 (example for a phase A to phase B fault).
=
V
A
- V
B
Z
app
I
A
- I
B
EQUATION1545 V1 EN-US
(Equation 35)
Section 7 1MRK 502 066-UUS B
Impedance protection
188
Technical manual