ERL F-PRO 116, User Manual

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D05125R01.20 F-PRO 116 User Manual 5-13
Where
θ = Thermal state in percentage at time t
θ
F
= Final thermal state before disconnection of feeder
I = Effective relay current.
I
θ
= Thermal overload setting

= Thermal time constant in minutes.
The final thermal state θ
F
for any steady state value of input current can be predicted using the
following formula.
θ
F
= I
2
/I
θ
2
* 100%
49
– Thermal Overload Logic diagram
Figure 5.11: Logic Diagram of 49 Function
Table 5.12: 49 Thermal Overload Settings
Setting Description Range
Function Activation Enable/disable
Thermal Overload Pick up
0.2 to 2.0A (1A) / 1.0 to 10.0 A (5A)
Time constant(

))
0.5 to 100.0 Min.
Negative Sequence Weighing Factor(K) 0.0 to 10.0
Thermal Overload Alarm
Enable/Disable
Pickup % th
50% to 100%