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Instruction manual
–
AQ G3x7 Generator protection IED
129 (211
)
voltage difference on the current carrying elements of the network draws cyclically high
currents. The calculated impedance moves alo
ng lines “Pole slipping” as it is indicated in
figure below on the impedance plane. (The stable swings return to the same quadrant of
the
impedance plane along lines “Stable swing”.)
Figure 3-78 Pole slipping
The characteristic feature of pole slipping is that the impedance locus leaves the
characteristic at a location, where the sign of the calculated resistance (e.g
–
Rleaving) is
opposite to that of the entering location (e.g. +R
entering
).
If basically other protections on the network are expected to stop the pole slipping, then
more than one vector revolution is permitted. In this case the number of the revolution can
be set higher then 1, and the subsequent revolution is expected with
in a defined “Dead
t
ime”, also
set by parameter.
The duration of the generated trip pulse is a parameter value.
3.2.22.2
Main features
The main features of the pole slipping protection function are as follows:
•
A full-scheme system provides continuous measurement of impedances separately
in three independent phase-to-phase measuring loops.
•
Impedance calculation is conditional on the values of the positive sequence currents
being above a defined value.