Thermal Overload Protection - Siemens siprotec 7SA6 User Manual

10.17 Thermal Overload Protection

Setting Ranges
Calculation
Method
Tripping
Characteristic
Drop-off
Ratios
Tolerances
Influencing
Quantities
relating to k · I
N
7SA6 Manual
C53000-G1176-C133-1
Factor k according to IEC 60255–8
Time factor
Alarm temperaturerise
Current alarm stage
1
) Secondary values based on I
Calculation method temperaturerise
Tripping characteristic
) ≤ 8
·
for (I/ k
I
N
Meaning of abbreviations:
Θ/Θ
trip
Θ/Θ
alarm
I/I
alarm
Relating to k · I
N
Relating to
Tripping time
1
) Secondary values based on I
Auxiliary direct voltage range
0.8 ≤ U ≤ 1.15
/U
DC NDC
Temperaturerange
–5 °C ≤ ϑ ≤ 55 °C
amb
Frequency range
0.95 ≤ f/f ≤ 1.05
N
0.10 to 4.00
τ
1.0 min to 999.9 min (steps 0.1 min)
Θ
/Θ 50 % to 100 % related to the trip
alarm trip
temperaturerise
I 0.10 A to 4.00 A
alarm
= 1 A; for I = 5 A they must be multiplied with 5.
N N
maximum temperaturerise of 3 phases
means of temperaturerise of 3 phases
temperature rise from maximum current
see Figure 10-6
τ ⋅
t
=
t Tripping time
τ
Temperature rise time factor
Load current
I
I Previous load current
pre
k Setting factor according to
IEC 60255–8
I Rated current of protected object
N
drop-off with Θ
approx. 0.99
approx. 0.97
2 %, or. 10 mA
IEC 60 255–8
3 %, or. 1 s; class 3 % according to
IEC 60 255–8 for I/(k ·I
= 1 A; for I = 5 A they must be multiplied by 5.
N N
1 %
0.5 %/10 K
1 %
Technical Data
(steps 0.01)
(steps 1 %)
1
) (steps 0.01 A
2
I
2
   
I
pre
------------ - – ------------ -
   
⋅ ⋅
k I k I
N N
ln
------------------------------------------------ -
2
 
I
------------ - – 1
 
⋅
k I
N
alarm
1
); class 2 % according to
) > 1.25
N
1
)
10-35