Minimum Operating Current; Measuring Principles - ABB Relion 670 Series Technical Reference Manual

Section 6
Impedance protection
6.9.2.3
6.9.2.4
310
X
Non-directional
IEC05000182 V1 EN
Figure 161: Directional operating modes of the distance measuring zones

Minimum operating current

The operation of Distance measuring zones, quadrilateral characteristic (ZMRPDIS,
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 can 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
The phase-to-phase loop AB (BC or CA) is blocked if I
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

Measuring principles

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
X
R
Forward
1MRK505222-UUS C
X
R
Reverse
en05000182.vsd
0
< IMinPUPP.
AB (BC or CA)
Technical reference manual
R
.