ABB RELION REX640 Technical Manual page 1388

Condition monitoring functions
The two differential equations are shown in
D
∆ θ
∆
D θ
Where
Δθ
hr
The constants Շ
and are obtained from the Load factor calculation and parameter selection module.
The rated hot-spot to top oil gradient, HS_TOIL_GRA (Δθ
formula as shown in
∆
θ
hr
Where
I
rated
Hotspot Tmp rise
Top oil Tmp rise
Current type test
At each time step, the n
(n-1) value; the solutions of which are combined in accordance with the hot-spot
temperature rise equation.
∆ θ
h n
∆ θ
h
The initial conditions are calculated by setting the time derivative equal to zero
inDΔθ
1388
Dt
(
k
= ⋅ ⋅ ∆
( )
( )
h n 1
21
k
⋅ τ
22 w
Dt
= ⋅
( )
h 2 n  
 
1
 
⋅
 
τ
 
o
   
k
 22 
Hot-spot-to-top-oil gradient at rated current [°C]
, k , k
w 21 22
Equation 328
−
Hotspot Tmp rise Top oil Tmp rise
=
 
Current type test

I

rated
Rated current of the transformer
Hot-spot temperature rise over ambient at rated load
Top oil temperature rise over ambient at rated load
Current applied in type testing to reach rated hot-spot temperature
th
D
= ∆ θ + ∆ θ
( ) ( ) ( )
1 h n 1 − 1 h n 1
D
= ∆ θ + ∆ θ
( ) ( ) ( )
2 n h 2 n − 1 h 2 n
and DΔθ equations, resulting in the following equations.
h1(n) h2(n)
Equation 326
)
y
K
θ ⋅ − ∆ θ
( )
hr
h n 1 − 1
(
( )
− ⋅ ∆ ⋅ − ∆
y
k
1 θ K θ
hr
21
and y are varying according to the
.
y



value of DΔθ and DΔθ
h1(n)
Equation 327
and
)
( ( )
−
h 2 n 1
Cooling mode setting
), is calculated using the
hr
are calculated from the
h2(n)
Technical Manual
1MRS759142 F
.
(Equation 326)
(Equation 327)
(Equation 328)
(Equation 329)
(Equation 330)
REX640