CHAPTER 4: SETPOINTS MONITORING
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL 4–291
Table 4-36: RTD Temperature vs. Resistance
NOTE:
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 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
TEMPERATURE RESISTANCE (IN OHMS)
°C °F 100 Ω PT
(IEC 60751)
120 Ω NI 100 Ω NI 10 Ω CU
–40 –40 84.27 92.76 77.30 7.49
–30 –22 88.22 99.41 82.84 7.88
–20 –4 92.16 106.15 88.45 8.26
–10 14 96.09 113.00 94.17 8.65
0 32 100.00 120.00 100.00 9.04
10 50 103.90 127.17 105.97 9.42
20 68 107.79 134.52 112.10 9.81
30 86 111.67 142.06 118.38 10.19
40 104 115.54 149.79 124.82 10.58
50 122 119.40 157.74 131.45 10.97
60 140 123.24 165.90 138.25 11.35
70 158 127.08 174.25 145.20 11.74
80 176 130.90 182.84 152.37 12.12
90 194 134.71 191.64 159.70 12.51
100 212 138.51 200.64 167.20 12.90
110 230 142.29 209.85 174.87 13.28
120 248 146.07 219.29 182.75 13.67
130 266 149.83 228.96 190.80 14.06
140 284 153.58 238.85 199.04 14.44
150 302 157.33 248.95 207.45 14.83
160 320 161.05 259.30 216.08 15.22
170 338 164.77 269.91 224.92 15.61
180 356 168.48 280.77 233.97 16.00
190 374 172.17 291.96 243.30 16.39
200 392 175.86 303.46 252.88 16.78
210 410 179.53 315.31 262.76 17.17
220 428 183.19 327.54 272.94 17.56
230 446 186.84 340.14 283.45 17.95
240 464 190.47 353.14 294.28 18.34
250 482 194.10 366.53 305.44 18.73
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