Onload Tap Changer - GE 845 Instruction Manual

CHAPTER 4: SETPOINTS
NOTE:

Onload Tap Changer

845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
TOP-OIL TEMPERATURE
Range: Computed, RTD 1, RTD 2....RTD x
Default: Computed
Select RTD input for direct measurement of top-oil temperature. If such input is not
available, select the setting "Computed".
Refer to SETPOINTS/RTD Temperature, on how to select RTD, to be used for measuring
ambient and top-oil temperatures.
This section contains the settings to configure the tap position input. The 845 relay offers
tap position detection by Binary Coded Decimal (BCD) inputs. Based on the detected tap,
the 845 relay dynamically corrects for CT ratio mismatch resulting from the changes of the
voltage ratio of the transformer. Thus, the percent differential function of the device can be
set for greater sensitivity. See Section: Transformer Setup > Magnitude Compensation >
item 2. LTC compensation set to "Enabled", for more details on the tap position input.
Tap detection using BCD input
The Binary Coded Decimal (BCD) is another way of detecting tap position by using the
combination of six bits each driven by contact input. The user wires and selects the
contact input per bit number. Each combination of six bits corresponds to a certain tap
position. Refer to the following table: All BCD combinations supported by the relay:
Path:
Setpoints > Monitoring > Transformer > Tap Changer
..\Transformer\Tap Changer
Item Name
Tap Position Detection
TC Winding Currents
Tap Detection Input
Min Tap
Neutral Tap
Max Tap
Min Tap Voltage
Voltage Increment per Tap
BCD Bit 1 Input
BCD Bit 2 Input
BCD Bit 3 Input
BCD Bit 4 Input
BCD Bit 5 Input
BCD Bit 6 Input
Inverse Tap Position
Events
Targets
Tap Chnr
TAP POSITION DETECTION
Range: Disabled, Enabled
Default: Disabled
TC WINDING CURRENTS
Range: None, J1, K1, K2
Default: None
Enter the CT bank associated with the winding with tap changer. Enter 'None' if the
transformer is not equipped with a tap changer. Enter 'None' if automatic magnitude
compensation based on tap position used for the differential protection is not needed.
The setting "None" can be selected in cases where either the transformer is not
equipped with Tap Changer, or it is equipped with Tap Changer, but it is not desired to
Value Unit
Disabled
None
BCD
16
0
16
61.00 kV
0.50 kV
Off
Off
Off
Off
Off
Off
Disabled
Enabled
Self Reset
SYSTEM
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