GE 845 Instruction Manual page 356

MONITORING
..\System\Transformer\Thermal Inputs
Setpoints
Winding Currents
Ambient Temperature
January
February
March
April
May
June
July
August
September
October
November
December
Top-Oil Temperature
<< Thermal
Status
NOTE:
4–252
2
P =I *R, where I is the winding rated current, and R is the three phase series
R n(W) n(W)
resistance.
• Refer to Setpoints > System > Transformer > Thermal Inputs menu, and select the
inputs for Ambient temperature and Top-Oil temperature. If no transducer is available
to measure Ambient temperature, select the "Monthly Average" setting, and enter the
approximate average temperature per month in the monthly calendar menu. If Top-
Oil temperature measurement is not available, select the setting "Computed".
Value Unit
CT Bank 1-J1
Monthly Average
-20 ° C
-20 ° C
-20 ° C
7 ° C
15 ° C
25 ° C
30 ° C
30 ° C
20 ° C
17 ° C
14 ° C
9 ° C
Computed
Tap Chan
To change the temperature unit, i.e. Fahrenheit, Celsius go to Setpoints > Device > Front
Panel menu.
The inputs for Ambient Temperature and Top-Oil Temperature from Thermal Inputs menu
include selection of RTDs. The selected RTDs must be programmed, for the temperature to
be measured on the relay and be included in the calculation for hottest-spot winding
temperature.
Winding Hottest
HOTTEST-SPOT TEMPERATURE
The Hottest-Spot Temperature element provides the mechanism for detecting the hottest-
spot winding temperatures inside the transformer. It can be set to alarm or trip in cases
where the hottest-spot temperature (as computed by the relay) is above the PKP threshold
for the specified time, this is considered an overheated transformer.
Path:
Setpoints > Monitoring > Transformer > Hottest-Spot Temperature
..\Transformer\Wndg Hottest Spot
Item Name
Function
Pickup
Pickup Delay
Block
Output Relay X
Events
Targets
Hot Spot
FUNCTION
Range: Disabled, Alarm, Latched Alarm, Configurable
Default: Disabled
..\Setpoints\RTD Temperature\RTD 1
Setpoints
Function
Name
Type
Trip Temperature
Trip Pickup Delay
Trip Dropout Delay
Trip Output Relay X
Alarm Function
Alarm Temperature
Alarm Pickup Delay
Alarm Dropout Delay
Alarm Output Relay X
Sensor Open
Block
Events
Targets
RTD 1
RTD 2
Value
Disabled
140
1
Off
Do Not Operate
Enabled
Self Reset
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS
Value Unit
Disabled
RTD 1
100 W Platinum
155 º C
2 s
0 s
Do Not Operate
Disabled
130 º C
2 s
0 s
Do Not Operate
None
Off
Enabled
Latched
RTD 3 >>
RTD 4
Unit
°C
min