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Protection and Automation Functions
6.22 Unbalanced-Load Protection
required. The technical data of the machine is provided in the Technical Data Sheet of the machine manufac-
turer.
EXAMPLE
The following example shows the setting of the parameter Max. continuously perm. I2 . The value 10
% is selected in the example.
To avoid issuing the
eter Warning delay in the range of 10 s to 20 s is practicable. 15 s is selected in the example.
[dwunbloc-030812, 1, en_US]
Figure 6-178
Parameter: Unbalanced load factor K
•
Default setting (_:11011:102) Unbalanced load factor K = 15 s
Unbalanced load factor K can be derived from the unbalanced-load characteristic according to
Figure
6-178. You can read the time corresponding to Unbalanced load factor K at the point I
I
= 1. In the example, this is the p.u. value 10° which corresponds to a time of 15 s. As the example
rated,machine
shows, the time is often written directly on the characteristic curve.
Parameter: Cooling time therm.replica
•
Default setting (_:11011:103) Cooling time therm.replica = 1500 s
The parameter Cooling time therm.replica establishes the time required by the protected object to
cool down the thermal replica to the initial value. If the machine manufacturer does not provide this informa-
tion, the setting value of Cooling time therm.replica can be calculated from the setting values of
Unbalanced load factor K and Max. continuously perm. I2 by the formula in the following
example.
690
Warning indication too fast, Siemens recommends a longer delay. Setting the param-
Example of an Unbalanced-Load Characteristic Specified by the Machine Manufacturer
SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
/
2
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