Functions
2.8 Motor Protection
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
179
Figure 2-61 Example of a complete motor protection characteristic
Example:
Motor with the following data:
The setting for address 4402 Load Jam I> as secondary value is calculated as follows:
The tripping delay time can remain at the default setting of 1 s. The warning threshold is set to 75% of the trip-
ping element (4404 I Alarm ≡ 0.95 A sec.).
The tripping delay time can remain at the default setting of 2 s.
In order to block the function during motor startup, the parameter 4406 T Start Blk. is set to double startup
time (T Start Blk. = 2 · 8.5 s = 17 s).
Nominal voltage V
Nom
= 6600 V
Nominal current I
Nom
= 126 A
Long-term current rating I
max
= 135 A
Startup duration T
startmax.
= 8.5 s
Current transformer I
NomCTprim
/ I
NomCTsec
= 200 A / 1 A
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