∆ = ⋅ ∆ ⋅
( )
θ θ
h
hr
y
k K
1 0
21
(Equation 331)
∆ = −
( )
⋅ ∆ ⋅
( )
θ θ
h
hr
y
k K
2 0
21
1
(Equation 332)
The final hot-spot temperature is calculated as the sum of top oil temperature and
the rise of hot-spot temperature over the top oil temperature.
The hot-spot temperature at the nth time step is calculated as shown in
Equation
333
.
HOTSPOT TEMP
o n h n
_
( ) ( )
= + ∆
θ θ
(Equation 333)
The calculated hot-spot temperature HOTSPOT_TEMP and rated hot-spot to top oil
gradient, HS_TOIL_GRA are available in the Monitored data view.
7.3.5.4 Level detector 1
This module compares the calculated hot-spot temperature, HOTSPOT_TEMP value
with the
Alarm level
and
Warning level
settings.
If HOTSPOT_TEMP is greater than the
Warning level
, the module activates the
WARNING output after a settable
Warning delay time
.
If HOTSPOT_TEMP is greater than the
Alarm level
, the module activates the ALARM
output after a settable
Alarm delay time
.
Assuming existing conditions, as long as the alarm/warning conditions are
not reached, the module calculates the available load reserve in percentage to
reach the alarm condition LD_RSV_ALM_PCT and to reach the warning condition,
LD_RSV_WRN_PCT. These outputs can be obtained from the Monitored data view.
If the warning condition is reached, the LD_RSV_WRN_PCT output is forced to zero
and if the alarm condition is reached, LD_RSV_ALM_PCT is forced to zero.
The load reserve outputs are only indicative and are calculated based
on rated current, assuming the same ambient temperature and cooling
modes. If, for any reason, the load reserve calculation is not feasible, the
load reserve outputs are shown as zero.
The binary input BLOCK can be used to block the function. The activation of the
BLOCK input deactivates WARNING and ALARM outputs and resets the internal timers.
7.3.5.5 Ageing and loss of life calculation
This module calculates the rate at which transformer insulation ageing is
accelerating compared with the ageing rate at rated hot-spot temperature and
equivalent ageing over a time period.
If transformer insulation paper is not upgraded, that is, if setting
Insul paper type
is
set to "Normal", the setting
Ageing rate method
selects between the IEC and IEEE
1MRS759142 F
Condition monitoring functions
REX640
Technical Manual
1389
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