5–40 745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
S2 SYSTEM SETUP CHAPTER 5: SETPOINTS
• AMBIENT RTD TYPE: The 745 provides an RTD input for monitoring the ambient
temperature. The three RTD types which may be used are 100 Ω platinum, and 100/
120 Ω nickel, the characteristics of which are as follows:
• AVERAGE AMBIENT TEMPERATURE (BY MONTH): This message is displayed only when
the
AMBIENT RTD TYPE is set for “By Monthly Average”. Ambient temperature is used in
the calculation of Insulation Aging and must be enabled for the function to operate.
Table 5–3: RTD resistance vs. temperature
Temperature 100 Ω Platinum 120 Ω Nickel 100 Ω Nickel
–50°C 80.31 Ω 86.17 Ω 71.81 Ω
–40°C 84.27 Ω 92.76 Ω 79.13 Ω
–30°C 88.22 Ω 99.41 Ω 84.15 Ω
–20°C 92.16 Ω 106.15 Ω 89.23 Ω
–10°C 96.09 Ω 113.00 Ω 94.58 Ω
0°C 100.00 Ω 120.00 Ω 100.00 Ω
10°C 103.90 Ω 127.17 Ω 105.60 Ω
20°C 107.79 Ω 134.52 Ω 111.20 Ω
30°C 111.67 Ω 142.06 Ω 117.10 Ω
40°C 115.54 Ω 149.79 Ω 123.01 Ω
50°C 119.39 Ω 157.74 Ω 129.11 Ω
60°C 123.24 Ω 165.90 Ω 135.34 Ω
70°C 127.07 Ω 174.25 Ω 141.72 Ω
80°C 130.89 Ω 182.84 Ω 148.25 Ω
90°C 134.70 Ω 191.64 Ω 154.90 Ω
100°C 138.50 Ω 200.64 Ω
161.78 Ω
110°C 142.29 Ω 209.85 Ω 168.79 Ω
120°C 146.06 Ω 219.29 Ω 175.98 Ω
130°C 149.82 Ω 228.96 Ω 183.35 Ω
140°C 153.58 Ω 238.85 Ω 190.90 Ω
150°C 157.32 Ω 248.95 Ω 198.66 Ω
160°C 161.04 Ω 259.30 Ω 206.62 Ω
170°C 164.76 Ω 269.91 Ω 214.81 Ω
180°C 168.47 Ω 280.77 Ω 223.22 Ω
190°C 172.46 Ω 291.96 Ω 243.30 Ω
200°C 175.84 Ω 303.46 Ω 252.88 Ω
210°C 179.51 Ω 315.31 Ω 262.76 Ω
220°C 183.17 Ω 327.54 Ω 272.94 Ω
230°C 186.82 Ω 340.14 Ω 283.94 Ω
240°C 190.45 Ω 353.14 Ω 294.28 Ω
250°C 194.08 Ω 366.53 Ω 305.44 Ω
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