GE C60 Instruction Manual page 388

5.7 CONTROL ELEMENTS
• I = protected element base (nominal) current
B
To ensure element accuracy for high overcurrent conditions, the maximum value of I/(k x I
istically it is exceeding this value.
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
5
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
5-252
τ
×
t ln
=
rst rst
Figure 5–113: IEC 255-8 SAMPLE OPERATE AND RESET CURVES
C60 Breaker Protection System
2
 
( kI )
B
 ---------------------------- - 
T
+
min
2 2
 
( )
I kI
–
B
> k × I , element starts increasing the thermal energy:
n B
5 SETTINGS
) is limited to 8, even when real-
B
(EQ 5.23)
GE Multilin