GE T60 Instruction Manual page 578

CONTROL ELEMENTS
τ = thermal protection trip time constant
rst
T = 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
thermal energy:
When current is less than the dropout level, I
where
5-360
Figure 5-213: IEC 255-8 sample operate and reset curves
> 0.97 × k × I , the element starts decreasing the thermal energy:
n B
> k × I , element starts increasing the
n B
T60 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS
Eq. 5-60
Eq. 5-61