4.50
SEL-787 Relay
Instruction Manual
Date Code 20081022
Protection and Logic Functions
RTD-Based Protection
RTD Trip/Warning Levels
The SEL-787 provides temperature warnings and trips through use of the RTD
temperature measurements and the warning and trip temperature settings in
The relay issues a temperature warning if any of the healthy RTDs indicate a
temperature greater than the relay RTD warning temperature setting. The relay
issues a temperature trip if one of the healthy RTDs indicate a temperature
greater than the RTD trip temperature setting.
To disable any of the temperature warning or trip functions, set the appropriate
temperature setting to OFF.
Only healthy RTDs can contribute temperatures to the warning and trip
functions. The relay includes specific logic to indicate if RTD leads are
shorted or open.
lists the RTD resistance versus temperature for the four supported
RTD types.
Table 4.17
RTD Resistance versus Temperature
Temp
(°F)
Temp
(°C)
100
Platinum
120
Nickel
100
Nickel
10
Copper
–58
–50.00
80.31
86.17
74.30
7.10
–40
–40.00
84.27
92.76
79.10
7.49
–22
–30.00
88.22
99.41
84.20
7.88
–4
–20.00
92.16
106.15
89.30
8.26
14
–10.00
96.09
113.00
94.60
8.65
32
0.00
100.00
120.00
100.00
9.04
50
10.00
103.90
127.17
105.60
9.42
68
20.00
107.79
134.52
111.20
9.81
86
30.00
111.67
142.06
117.10
10.19
104
40.00
115.54
149.79
123.00
10.58
122
50.00
119.39
157.74
129.10
10.97
140
60.00
123.34
165.90
135.30
11.35
158
70.00
127.07
174.25
141.70
11.74
176
80.00
130.89
182.84
148.30
12.12
194
90.00
134.70
191.64
154.90
12.51
212
100.00
138.50
200.64
161.80
12.90
230
110.00
142.29
209.85
168.80
13.28
248
120.00
146.06
219.29
176.00
13.67
266
130.00
149.82
228.96
183.30
14.06
284
140.00
153.58
238.85
190.90
14.44
302
150.00
157.32
248.95
198.70
14.83
320
160.00
161.04
259.30
206.60
15.22
338
170.00
164.76
269.91
214.80
15.61
356
180.00
168.47
280.77
223.20
16.00
374
190.00
172.46
291.96
231.80
16.39
392
200.00
175.84
303.46
240.70
16.78
410
210.00
179.15
315.31
249.80
17.17
428
220.00
183.17
327.54
259.20
17.56
446
230.00
186.82
340.14
268.90
17.95
464
240.00
190.45
353.14
278.90
18.34
482
250.00
194.08
366.53
289.10
18.73
Summary of Contents for SEL-787
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