8.7.1 Identification
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Thermal overload protection, two time
constants
TRPTTR
SYMBOL-A V1 EN
49
8.7.2 Functionality
If a power transformer reaches very high temperatures the equipment might be
damaged. The insulation within the transformer will experience forced ageing. As a
consequence of this the risk of internal phase-to-phase or phase-to-earth faults will
increase.
The thermal overload protection estimates the internal heat content of the transformer
(temperature) continuously. This estimation is made by using a thermal model of the
transformer with two time constants, which is based on current measurement.
Two warning levels are available. This enables actions in the power system to be done
before dangerous temperatures are reached. If the temperature continues to increase to
the trip value, the protection initiates a trip of the protected transformer.
The estimated time to trip before operation is presented.
8.7.3 Function block
IEC06000272_2_en.vsd
TRPTTR
I3P*
BLOCK
COOLING
ENMULT
RESET
TRIP
START
ALARM1
ALARM2
LOCKOUT
WARNING
IEC06000272 V2 EN
Figure 182: TRPTTR function block
1MRK502052-UEN B Section 8
Current protection
401
Technical manual
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