Thermal Inputs - GE 845 Instruction Manual

SYSTEM
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Thermal Inputs

NOTE:
4–114
CURRENT SUPERVISION
Range: Disabled, Enabled
Default: Disabled
Current supervision can be used to add another element into one or another sensing
mechanism for detecting the Transformer Energized, or Transformer De-Energized
status. When "Enabled" the relay scans all the winding currents and compares the
measurements against the programmed setpoint "Minimum Current" level.
MINIMUM CURRENT
Range: 0.020 to 0.500 x CT in steps of 0.001
Default: 0.050 x CT
Select the minimum current, below which the transformer is considered de-energized.
If no load is connected to a transformer which has been energized, the current
transformers from the closed breaker will detect only the transformer magnetizing current.
In order to have Transformer energized status supervised by current, the level of the
minimum current must be below the transformer magnetizing current.
The 845 relay can be set to monitor the hottest-spot winding temperature, the aging
acceleration factor and the transformer insulation life. In order for the relay to perform the
correct calculations, the user needs to enter transformer data and program RTD inputs for
measuring ambient and top-oil temperatures. The following menu shows the selections for
ambient and top-oil temperatures.
Path:
Setpoints > System > Transformer > Thermal Inputs
..\Transformer\Thermal Inputs
Item Name
Winding Currents
Ambient Temperature
Ambient Temp Avg - Jan
Ambient Temp Avg - Feb
Ambient Temp Avg - Mar
Ambient Temp Avg - Apr
Ambient Temp Avg - May
Ambient Temp Avg - Jun
Ambient Temp Avg - Jul
Ambient Temp Avg - Aug
Ambient Temp Avg - Sep
Ambient Temp Avg - Oct
Ambient Temp Avg - Nov
Ambient Temp Avg - Dec
Top Oil Temperature
Thermal
WINDING CURRENTS
Range: CT Bank1-J1, CT Bank 2 – K1, CT Bank 3 –K2
Default: CT Bank 1-J1
Select the bank representing the currents (loading) of the winding to which the thermal
elements are applied.
AMBIENT TEMPERATURE
Range: Monthly Average, RTD 1, RTD 2....RTD x
Default: Monthly Average
Select RTD input if the ambient temperature is to be measured directly. Select the
"Monthly Average" setting and enter an average temperature for every month of the
year, if direct ambient temperature measurement is not available.
The setpoints for average monthly temperatures will show on the screen only when the
"Monthly Average" setting is selected. In all other cases, these setpoints will be hidden.
Value
CT Bank 1 -J1
Monthly Average
-20
-20
-10
10
20
30
30
30
20
10
10
-10
Computed
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS
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