GE N60 Instruction Manual page 295

5 SETTINGS
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
Figure 5–75: 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 N60 Network Stability and Synchrophasor Measurement System
2
 ( ) 
kI
B
τ × ---------------------------- -
t ln  
= +
rst rst
2 2
 
I ( kI )
–
B
> k × I
n
t Δ
E E -------------- -
= +
n n 1
– t
op In ( )
> 0.97 × k × I , the element starts decreasing the thermal energy:
n B
5.7 CONTROL ELEMENTS
) is limited to 8, even when real-
B
T
min
, element starts increasing the thermal energy:
B
(EQ 5.15)
5
(EQ 5.16)
5-165