Siemens SIPROTEC 7SJ61 Manual page 121

Figure 2-39
Example:
Motor with the following data:
Nominal voltage
Nominal current
Long-term current rating
Startup duration
Current transformer
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).
SIPROTEC, 7SJ61, Manual
C53000-G1140-C210-1, Release date 02.2008
Example of a complete motor protection characteristic
V
Nom
I
Nom
I = 135 A
max
T
startmax.
I
NomCTprim
= 6600 V
= 126 A
= 8.5 s
/ I = 200 A / 1 A
NomCTsec
Functions
2.6 Motor Protection
121