[logikdia-therm-ueberlst-wlk-010802, 1, en_US]
Figure 2-45
Logic diagram of the thermal overload protection
Setting Notes
General
A prerequisite for the application of the thermal overload function is that during the configuration of the func-
tional scope in address 142 49 = Enabled was set. At address 4201 FCT 49 the function can be turned ON or
OFF. Furthermore Alarm Only can be set. With the latter setting the protection function is active but only
outputs the indication
49 Winding O/L
(address 1517) when the tripping temperature is reached. The indi-
cation
49 Th O/L TRIP
(address 1521) is not generated.
k-Factor
The nominal device current is used as a basis for overload detection. The setting factor k is set under address
4202 49 K-FACTOR. It is determined by the relation between the permissible thermal continuous current and
this rated current:
[formel-therm-ueberl-k-fakt-1-oz-020802, 1, en_US]
The permissible continuous current is at the same time the current at which the e-function of the overtemper-
ature has its asymptote. It is not necessary to determine the tripping temperature since it results automatically
from the final rise temperature at k · Ι
N
. Manufacturers of electrical machines usually state the permissible
continuous current. If no data are available, k is set to 1.1 times the nominal current of the protected object.
For cables, the permissible continuous current depends on the cross-section, the insulation material, the
design and the method of installation, and can be derived from the relevant tables.
Please note that the overload capability of electrical equipment relates to its primary current. This has to be
considered if the primary current differs from the rated current of the current transformers.
2.7.2
Functions
2.7 Thermal Overload Protection 49
SIPROTEC 4, 7SD80, Manual 105
E50417-G1100-C474-A2, Edition 02.2018
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