Siemens Siprotec 7UM611 Manual page 74

Multi-functional generator protection relay 7um61 series
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2 Functions
Figure 2-18
The parameter 1705 T COOL DOWN establishes the time required by the protection
Cooldown Time
object to cool down under admissible unbalanced load I2> to the initial value. If the
machine manufacturer does not provide this information, the setting value can be cal-
culated by assuming an equal value for cool-down time and heatup time of the object
to be protected. The formula below shows the relation between the K asymmetry
factor and the cool-down time:
Example:
The following cool-down time results for a K = 20 s and an admissible continual unbal-
anced load I
74
Example of an Unbalanced Load Characteristic Specified by the Machine Man-
ufacturer
/I
= 11 %.
2
N
7UM61 Manual
C53000-G1176-C127-3

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