GE 845 Instruction Manual page 419

CHAPTER 4: SETPOINTS
NOTE:
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
Table 4-36: RTD Temperature vs. Resistance
TEMPERATURE
°C °F
–40 –40
–30 –22
–20 –4
–10 14
0 32
10 50
20 68
30 86
40 104
50 122
60 140
70 158
80 176
90 194
100 212
110 230
120 248
130 266
140 284
150 302
160 320
170 338
180 356
190 374
200 392
210 410
220 428
230 446
240 464
250 482
RTD type copper (Cu) is only available when order code option 'S' is chosen for Slot B or C.
RTD Protection
The 845 relay can monitor up to 13 RTDs, each of which can be configured to have a trip
temperature and an alarm temperature. The RTD Temperature protection menu will be
seen on the relay upon availability of RTD input/inputs. The minimum RTD Temperature
requirement for the user is to set the setpoint "Type". The default value for "Type", for each
RTD is "100 Ω Platinum". The protection RTD Trip, and RTD Alarm from the menu are
optional. They respond to directly measured RTD temperature. The Alarm temperature is
set slightly above the normal measured temperature for the transformer top-oil, bottom-
oil, or LTC oil. The Trip temperature is normally set at the maximum permissible oil
temperatures defined as dangerous for the transformer and the transformer insulation.
This element also monitors the RTD broken connection and blocks the RTD trip and alarm
functions if the RTD connection is detected as Open or Shorted and generates RTD Open
and RTD Shorted FlexLogic operands. An RTD is detected as Open when the RTD
RESISTANCE (IN OHMS)
100 Ω PT 120 Ω NI
(IEC 60751)
84.27 92.76
88.22 99.41
92.16 106.15
96.09 113.00
100.00 120.00
103.90 127.17
107.79 134.52
111.67 142.06
115.54 149.79
119.40 157.74
123.24 165.90
127.08 174.25
130.90 182.84
134.71 191.64
138.51 200.64
142.29 209.85
146.07 219.29
149.83 228.96
153.58 238.85
157.33 248.95
161.05 259.30
164.77 269.91
168.48 280.77
172.17 291.96
175.86 303.46
179.53 315.31
183.19 327.54
186.84 340.14
190.47 353.14
194.10 366.53
MONITORING
100 Ω NI 10 Ω CU
77.30 7.49
82.84 7.88
88.45 8.26
94.17 8.65
100.00 9.04
105.97 9.42
112.10 9.81
118.38 10.19
124.82 10.58
131.45 10.97
138.25 11.35
145.20 11.74
152.37 12.12
159.70 12.51
167.20 12.90
174.87 13.28
182.75 13.67
190.80 14.06
199.04 14.44
207.45 14.83
216.08 15.22
224.92 15.61
233.97 16.00
243.30 16.39
252.88 16.78
262.76 17.17
272.94 17.56
283.45 17.95
294.28 18.34
305.44 18.73
4–291