Instruction manual
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AQ G3x7 Generator protection IED
143 (211
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plane. These impedances are the positive sequence impedances in the measuring loops. The
protection compares these points with the
„offset circle” characteri
stics of the loss of excitation
protection, shown for stage 1 in figure below. For stage 2 the characteristic is the same with
independent parameters,
Parameter settings decide the size and the position of the circle. The center of the circle
can be on the positive R and negative X quadrant of the impedance plane. The R offset and
X offset values are defined to be positive in this quadrant.
Figure 3-86: Offset characteristics
If a measured impedance point is inside the circle, the algorithm generates the true value of
the related output binary signal.
The calculated impedance values are compared one by one with the setting values of the
„
offset circle” characteristics. This procedure is shown schematically in figure below.
The procedure is processed for each line-to-line loop. The result is the binary setting of
three status variables. This indicates that the calculated impedance is within the processed
“offset circle” characteristics.
