GE 745 - 7.4.5 Ambient Temperature Input; 7.4.5.1 Basic Calibration of RTD Input

CHAPTER 7: COMMISSIONING METERING
745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL 7–13
Now, applying 1 × CT into Winding 1 Phase A and the same current into Phase A Winding 2,
but 180° out-of- phase to properly represent CT connections, the total differential current
in the Phase A element will be (0.57 – 0.84) × CT = –0.26 × CT. The injection of currents into
Phase A of Windings 1 and 2 in this manner introduces a differential current of (–0.57 × CT
+ 0.42 × CT) = –0.15 × CT into Phase B and (0.0 × CT + 0.42 × CT) = 0.42 × CT into Phase C.
7.4.5 Ambient Temperature Input
7.4.5.1 Basic Calibration of RTD Input
 Enable ambient temperature sensing with the
S2 SYSTEM SETUP 
AMBIENT TEMP  AMBIENT TEMPERATURE SENSING setpoint.
 Connect a thermocouple to the relay terminals B10, B11, and B12 and
read through the A2 METERING
 AMBIENT TEMP  AMBIENT
TEMPERATURE actual value.
 Compare the displayed value of temperature against known temperature
at the location of the sensor.
Use a thermometer or other means of obtaining actual temperature.
An alternative approach is to perform a more detailed calibration per the procedure
outlined below.
7.4.5.2 Detailed Calibration of RTD Input
1. Alter the following setpoints. Set S2 SYSTEM SETUP
 AMBIENT TEMP  AMBIENT
TEMPERATURE SENSING to Enabled and set
S2 SYSTEM SETUP  AMBIENT TEMP 
AMBIENT RTD TYPE
to the desired type.
The measured values should be ±2°C or ±4°F.
2. Alter the resistance applied to the RTD input (note the 3-input connection must be
used for the measurements to be valid) as per the typical table below to simulate RTDs
and verify accuracy of the measured values.
3. View the measured values in A2 METERING
 AMBIENT TEMP  AMBIENT
TEMPERATURE.
Refer to RTD tables included in this manual for calibration of resistance versus
temperature.
Table 7–1: Measured RTD temperature
RTD type
100
Ω Platinum
resistance
Expected RTD reading Measured RTD temperature
____°C ____°F (select one)
°C °F
100 Ω Platinum 80.31 –50 –58
100.00 0 32
119.39 50 122
138.50 100 212
157.32 150 302
175.84 200 392
194.08 250 482