Instruction manual
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AQ G3x7 Generator protection IED
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o
True RMS value;
•
provide the pre-calculated current values to the subsequent software function
blocks,
•
deliver the calculated Fourier basic component values for on-line displaying.
The current input function block receives the sampled current values from the internal
operating system. The scaling (even hardware scaling) depends on parameter setting, see
parameters Rated Secondary I1-3 and Rated Secondary I4. The options to choose from are
1A or 5A (in special applications, 0.2A or 1A). This parameter influences the internal number
format and, naturally, accuracy. A small current is processed with finer resolution if 1A is
selected.
If needed, the phase currents can be inverted by setting the parameter Starpoint I1-3. This
selection applies to each of the channels IL1, IL2 and IL3. The fourth current channel can
be inverted by setting the parameter Direction I4. This inversion may be needed in
protection functions such as distance protection, differential protection or for any functions
with directional decision.
Figure 3-1 Example connection
Phase current CT:
CT primary 100A
CT secondary 5A
Ring core CT in Input I0:
I0CT primary 10A
I0CT secondary 1A
Phase current CT secondary currents starpoint is towards the line.
