2.8 Unbalanced Load Protection
207
7UT613/63x Manual
C53000-G1176-C160-2
Figure 2-92 Tripping characteristic of the definite time unbalanced load protection
Inverse Time Stage
The inverse time overcurrent stage operates with a tripping characteristic either ac-
cording to the IEC or the ANSI standard. The characteristics and their equations are
given in the „Technical Data“. The definite time elements I2>> and I2> are superim-
posed on the inverse time curve.
Pickup, Trip
The negative sequence current I
2
is compared to the set value I2p . When the nega-
tive sequence current exceeds 1.1 times the setting value, a pickup annunciation is
generated. The tripping time is calculated from the negative sequence current accord-
ing to the characteristic selected. After expiration of the time period a tripping
command is output. Figure 2-93 shows the qualitative course of the characteristic; the
overlapping I2>> stage is represented by a dashed line.
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