Instruction manual
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AQ G3x7 Generator protection IED
117 (211
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Three phase fault detection
The logic processing of diagrams in the following figures is sequential. If the result of one
of them is true, no further processing is performed.
Figure below shows that if
o
All three line-line loops caused start of the polygon impedance logic, and
o
the currents in all three phases are above the setting limit,
then a three-phase fault is detected and no further check is performed. The three-phase
fault detection resets only if none of the three line-to-line loops detect fault any longer.
Figure 3-68: Three phase fault
Table 3-49: Output signals for three phase start decision of the impedance protection
function.
