[beispiel-schieflastdiagram, 1, en_GB]
Figure 2-99 Example of a pre-defined asymmetrical load diagram
If, however, the asymmetrical load protection must be set in amps secondary during operation, also the K-
factor must be converted as it refers to the machine internal current. The following applies:
[schieflastschutz-k-sek, 1, en_GB]
Beispiel:
Machine
Ι
N
= 483 A
Ι
2zul
= 11 % (salient-pole machine)
K-Faktor = 20 s
Current transformer 500 A/5 A
results in the setting value under address 4034 FACTOR K:
[schieflastschutz-faktor-k, 1, en_GB]
The setting value 4035 T COOL DOWN is defined as the time required by the protected object to cool down
from 100 % to 0 % during prior stress with permissible asymmetrical load I2>. If the machine manufacturer
does not provide this information, the setting value can be calculated by assuming an equal value for cool-
down time and heatup time of the object to be protected. There is the following connection between the
asymmetrical factor K and the cool-down time:
[schieflastschutz-t-abkuehl, 1, en_GB]
Example:
For asymmetry factor K = 20 s and a permanently permissible asymmetrical load of Ι
2
/Ι
N
= 11 % a corre-
sponding cool-down time is derived
Functions
2.8 Unbalanced Load Protection
SIPROTEC 4, 7UT6x, Manual 197
C53000-G1176-C230-5, Edition 09.2016
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