ABB RELION REX640 Technical Manual page 1284

Section 7
Condition monitoring functions
1278
y
k K
θ θ
∆ = ⋅ ∆ ⋅
hr
h 21
1 0
( )
GUID-318FDA0E-9FB1-409A-B959-1CB9535A71D9 V1 EN
k K
1
θ θ
( )
∆ = − ⋅ ∆ ⋅
hr
h 21
2 0
( )
GUID-16670ACA-9A7B-4430-800B-EBB6DA0BB255 V1 EN
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 the
298.
HOTSPOT TEMP _
θ
=
o n
GUID-EFB5AB72-B20E-4F60-B6D7-7B525137EEB1 V1 EN
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.
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.
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.
y
θ
+ ∆
( ) h n ( )
1MRS759142 C
(Equation 296)
(Equation 297)
Equation
(Equation 298)
REX640
Technical Manual