1MDU07212-YN Rev. D Section 4
Protection and Control Function
REF601 / REJ601 / REM601 27
Application Manual
Thermal characteristic warming condition at diabatic behavior:
ϑ
1
= new value of thermal image
ϑ
0
= present value of thermal image
I = maximum value of measured phase currents
I
b
= base current (rated current/full load current defined by setting).
Δt = time interval between ϑ
0
and ϑ
1
τ↑ = Heating time constant
Thermal characteristic warming condition at adiabatic behavior:
The value of ϑ
0
at the start of the function (i.e. at power on of the
IED is defined by a setting
2. Constant thermal image of protected object:
During this condition, the dissipated heat is equal to heat generated by the current
flowing through the protected object.
The thermal model for this conditions is as follow:
whereas:
ϑ
1
= new value of thermal image
ϑ
0
= present value of thermal image
I = maximum value of measured phase currents
I
b
= base current (rated current/full load current defined by setting).
3. Cooling of protected object:
When the current reduces compared to previous condition or the motor has stopped
it results into cooling of an apparatus.
Cooling condition is defined when:
The thermal model used during cooling condition for standing objects (cable /
transformer / standing motor) is:
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