Parameter: Cool-down factor Tau
•
Default value (_:108) Cool-down factor Tau = 7.0
If the current becomes lower than the setting value of the Imin cooling parameter, you can set the Cool-
down factor Tau parameter to calculate the internal cooling time constant.
Parameter: Operate char. curve
•
Default value Operate char. curve = 1.1 p.u., 600.00 s
With the Operate char. curve parameter, you define the characteristic curve in a tabular form with
ordered normalized current values and associated normalized time values.
When setting the parameter, consider the following:
•
Set the current value as per-unit value with the rated current of the protected object as reference.
•
Set the time value in seconds.
•
Enter the values in continuous order.
EXAMPLE
With the following 12 points, you can get a user-defined characteristic curve as shown in the following figure.
Table 6-13 User-Defined Points
I / I
obj
t (s)
1.16 120.00
1.21 96.00
1.25 76.00
1.28 62.00
1.35 48.00
1.42 37.50
1.48 33.50
1.58 27.50
1.84 20.50
2.09 14.00
2.25 9.85
8.00 9.85
Protection and Automation Functions
6.20 Thermal Overload Protection, User-Defined Characteristic Curve
672 SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
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