Siemens SIPROTEC 4 7UT6 Series Manual page 188

Functions
2.8 Unbalanced Load Protection
[schieflast-ausloesekennlinie-020926-rei, 1, en_GB]
Figure 2-94
Inverse Time Stage
The inverse time overcurrent stage operates with a tripping characteristic either according to the IEC or the
ANSI standard. The characteristics and their equations are given in the "Technical Data". The definite time
elements Ι2>> and Ι2> are superimposed on the inverse time curve.
Pickup, Trip
The negative sequence current Ι
exceeds 1.1 times the setting value, a pickup annunciation is generated. The tripping time is calculated from
the negative sequence current according to the characteristic selected. After expiration of the time period a
tripping command is output.
Ι2>> stage is represented by a dashed line.
[schieflast-ausloesecharakteristik-020926-rei, 1, en_GB]
Figure 2-95
188
Tripping characteristic of the definite time unbalanced load protection
is compared to the set value I2p . When the negative sequence current
2
Figure 2-95 shows the qualitative course of the characteristic; the overlapping
Inverse time characteristic for unbalanced load protection
SIPROTEC 4, 7UT6x, Manual
C53000-G1176-C230-5, Edition 09.2016