CHAPTER 4: SETPOINTS
MONITORING
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
4–291
Table 4-36: RTD Temperature vs. Resistance
NOTE
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
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
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
Summary of Contents for 845
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Page 526: ...6 22 845 TRANSFORMER PROTECTION SYSTEM INSTRUCTION MANUAL FLEXELEMENTS CHAPTER 6 METERING ...