Siemens SIPROTEC 4 7UT6 Series Manual page 190

Functions
2.8 Unbalanced Load Protection
[logikdia-schieflastschutzes-bsp-iec-kennlinie, 1, en_GB]
Figure 2-96
Thermal Stage
With the aid of the thermal stages the unbalanced load protection can be well adapted to the thermal loading
of the electrical motor rotor during asymmetric load.
Pickup, Warning
The permissible continuous load imbalance is determined with the setting I2>. If this value is exceeded, it
applies as "Pickup" for the negative sequence protection. At the same time this sets the alarm stage: After a set
time T WARN has expired, a warning message
Thermal Characteristic
The thermal characteristic allows an approximate calculation of the thermal loading of the electrical motor
rotor by load imbalance in the stator. This follows the simplified equation:
[thermische-kennlinie, 1, en_GB]
190
Logic diagram of the unbalanced load protection - illustrated for IEC characteristic
I2 th. Warn is given.
SIPROTEC 4, 7UT6x, Manual
C53000-G1176-C230-5, Edition 09.2016