Siemens siprotec 7SA6, Manual

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Technical Data
10-40
7SA6 Manual
C53000-G1176-C156
10.18 Thermal Overload Protection
Setting Ranges Factor k according to IEC 60255–8 0.10 to 4.00 (steps 0.01)
Time factor
τ
1.0 min to 999.9 min (steps 0.1 min)
Alarm temperaturerise
Θ
alarm
/
Θ
trip
50 % to 100 % related to the trip
temperaturerise
(steps 1 %)
Current alarm stage I
alarm
0.10 A to 4.00 A
1
) (steps 0.01 A)
1
) Secondary values based on I
N
= 1 A; for I
N
= 5 A they must be multiplied with 5.
Calculation
Method Calculation method temperaturerise maximum temperaturerise of 3 phases
means of temperaturerise of 3 phases
temperature rise from maximum current
Tripping
Characteristic see Figure 10-6
Drop-off
Ratios
Θ
/
Θ
trip
drop-off with
Θ
alarm
Θ
/
Θ
alarm
approx. 0.99
I
/
I
alarm
approx. 0.95
Tolerances Relating to k ·
I
N
2 %, or. 10 mA
1
); class 2 % according to
IEC 60 255–8
Relating to
Tripping time
3 %, or. 1 s; class 3 % according to
IEC 60 255–8 for I/(k ·I
N
) > 1.25
1
) Secondary values based on I
N
= 1 A; for I
N
= 5 A they must be multiplied by 5.
t
τ
I
k I
N
⋅
-------------
è ø
æ ö
2
I
pre
k I
N
⋅
-------------
è ø
æ ö
2
–
I
k
I
N
⋅
-------------
è ø
æ ö
2
1
–
-------------------------------------------------
ln
⋅
=
Tripping characteristic
t Tripping time
τ
Temperature rise time factor
I Load current
I
pre
Previous load current
k Setting factor according to
IEC 60 255–8
I
N
Rated current of protected object
Meaning of abbreviations:
for ( I / k
·
I
N
)
≤
8