ABB RELION REX640 Technical Manual page 1387

1MRS759142 F
D θ
0
Where
θ
0(n)
θ
a
Δθ
or
R
, Շ
k
11
The D operator implies a difference in the associated variable that corresponds to
each time step Dt. At each time step, the n
(n-1)
The initial conditions are calculated by setting the time derivative equal to zero in
Dθ
0(n)
θ
( )
0 0
The top oil temperature at the n
TOPOIL TEMP
The measured/calculated top oil temperature TOPOIL_TEMP is available in the
Monitored data view.
7.3.5.3 Hot-spot temp calculation
Winding hot-spot temperature depends on the winding temperature rise due to the
load factor and oil flow. These two factors act complimentary to each other in the
influence of temperature rise.
The differential equations for hot-spot temperature rise above top oil temperature
is solved as the sum of two differential equations.
∆ θ
h n
REX640
Technical Manual
  (

+ ⋅
2
K
1
Dt 

= ⋅
( ) 
( )
⋅ +
n

k R
τ 1


11 o

Top oil temperature in the tank at n
Ambient temperature [°C]
Top oil temperature rise over ambient temperature at rated load, given by the
Top oil Tmp rise
setting
Ratio of losses at rated current to no load losses, given by the setting
losses
, K and x are as defined in the Parameter selection module in
0
th
value.
equation, resulting in the following equations.
( )
x
 
+ ⋅
2
K R
1
 
= ⋅ ∆ +
θ
+ or
 
1 R
 
D
_ = θ +
( )
n
0 − 1
If the top oil temperature sensor is valid, the TOPOIL_TEMP output is
equal to the measured top oil temperature TOIL_TEMP input.
= ∆ θ − ∆ θ
( ) ( ) ( )
h n 1 h 2 n
)
x

R


⋅ ∆ − −
θ θ θ
 ( )
−
or a
0 n 1


th
time step
th
value of Dθ
θ
a
th
time step is calculated as shown below.
θ
( )
n
0
Condition monitoring functions







Figure 789
is calculated from the
0(n)
(Equation 322)
Ratio of
.
(Equation 323)
(Equation 324)
(Equation 325)
1387