Sel SEL-787 - Table 4.19 RTD Resistance Versus Temperature

4.47
Date Code 20150130 Instruction Manual SEL-787 Relay
Protection and Logic Functions
RTD-Based Protection
RTD Location
The relay allows you to independently define the location of each monitored
RTD by using the RTD location settings.
Define the RTD location settings through use of the following suggestions:
➤ If an RTD is not connected to an input or has failed in place and
will not be replaced, set the RTD location for that input equal to
OFF.
➤ For the input connected to an RTD measuring ambient air
temperature, set the RTD location equal to AMB. Only one
ambient temperature RTD is allowed.
➤ For inputs connected to monitor temperatures of apparatus,
such as transformer oil and winding temperature, set the RTD
location equal to OTH. Use the RTD identifier setting to assign
an appropriate name to the RTD, for example set
RTD1NAM := XFRMR1 OIL.
If an RTD location setting is equal to OFF, the relay does not request that an
RTD type setting be entered for that input.
RTD Type
The four available RTD types are:
➤ 100-ohm platinum (PT100)
➤ 100-ohm nickel (NI100)
➤ 120-ohm nickel (NI120)
➤ 10-ohm copper (CU10)
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
Table 4.18.
The relay issues a temperature warning if any of the healthy RTDs indicates a
temperature greater than the relay RTD warning temperature setting. The relay
issues a temperature trip if one of the healthy RTDs indicates 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.
Table 4.19 lists the RTD resistance versus temperature for the four supported
RTD types.
Table 4.19 RTD Resistance Versus Temperature (Sheet 1 of 2)
Temp
(°F)
Tem p
(°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
NOTE: To improve security, RTD
ALARM and TRIP are delayed by
approximately 6 seconds.