ABB RELION 620 Series Technical Manual page 333

1MRS757644 F
620 series
Technical Manual
Temperature estimator
The final temperature rise is calculated from the highest of the three-phase currents
according to the expression:
2
 
I
T
Θ = ⋅
 
final ref
 
I
ref
 
GUID-06DE6459-E94A-4FC7-8357-CA58988CEE97 V2 EN
I highest measured phase current
Current reference setting
I the set value of the
ref
Temperature rise setting (temperature rise (°C) with the steady-state current I
T the set value of the
ref
The ambient temperature value is added to the calculated final temperature rise
estimation. If the total value of temperature is higher than the set operate temperature
level, the START output is activated.
The Current reference setting is a steady-state current that gives the steady-state end
temperature value Temperature rise. It gives a setting value corresponding to the rated
power of the transformer.
The Temperature rise setting is used when the value of the reference temperature rise
corresponds to the Current reference value. The temperature values with the
corresponding transformer load currents are usually given by transformer
manufacturers.
Thermal counter
T2PTTR applies the thermal model of two time constants for temperature
measurement. The temperature rise in degrees Celsius (°C) is calculated from the
highest of the three-phase currents according to the expression:
2
 
 
I
 
p * * T
∆Θ =  
ref
 
 I 
ref
 
 
 
GUID-27A879A9-AF94-4BC3-BAA1-501189F6DE0C V2 EN
ΔΘ calculated temperature rise (°C) in transformer
I measured phase current with the highest TRMS value
Current reference setting (rated current of the protected object)
Iref the set value of the
Temperature rise setting (temperature rise setting (°C) with the steady-state
Tref the set value of the
current I )
ref
Weighting factor p setting (weighting factor for the short time constant)
p the set value of the
Δt time step between the calculation of the actual temperature
Short time constant setting (the short heating / cooling time constant)
the set value of the
t
1
Long time constant setting (the long heating / cooling time constant)
the set value of the
t
2
t
∆ 
 

I I
−
1 
 
1 e τ 1 p
( )
⋅ − + − ⋅ 

 I
 
ref


 

Section 4
Protection functions
2
t
 ∆
 

−
 2
 
T 1 e τ
 ⋅ ⋅ −
ref


 


 

(Equation 14)
ref
(Equation 15)
327