The R1 and jX1 in figure 133 represents the positive sequence impedance from the
measuring point to the fault location. The RFPG is presented in order to “convey” the
fault resistance reach.
The zone may be set to operate in , , Disabled or direction through the setting
OperationDir. The result from respective set value is illustrated in figure
134. It may
be convenient to once again mention that the impedance reach is symmetric, in the
sense that it is conform for forward and reverse direction. Therefore, all reach settings
apply to both directions.
en05000182.vsd
R
X
R
X
R
X
Non-directional Forward Reverse
IEC05000182 V1 EN
Figure 134: Directional operating modes of the distance measuring zone
6.5.2.3 Minimum operating current
The operation of the distance measuring zone 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 3I0.
1MRK505222-UUS C Section 6
Impedance protection
265
Technical reference manual
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