GE C70 Instruction Manual page 355

5 SETTINGS
The reset time of the thermal overload protection element is also time delayed using following formula:
In the above equation,
• τ = thermal protection trip time constant.
rst
• T is a minimum reset time setting
min
Figure 5–110: IEC 255-8 SAMPLE OPERATE AND RESET CURVES
The thermal overload protection element estimates accumulated thermal energy E using the following equations calculated
each power cycle. When current is greater than the pickup level, I
When current is less than the dropout level, I
GE Multilin


kI
B

 ---------------------------- -
t ln 
=
rst rst
2


I kI
–
E E
= +
n n 1
–
> 0.97 × k × I , the element starts decreasing the thermal energy:
n B
C70 Capacitor Bank Protection and Control System
2


 T
+
min
2


B
> k × I , element starts increasing the thermal energy:
n B
t 
-------------- -
t
 
op In
5.7 CONTROL ELEMENTS
(EQ 5.22)
(EQ 5.23)
5-231
5