Rockwell Automation Publication 825-UM004D-EN-P - November 2012 85
Configuring Protection & Logic Functions Chapter 6
If an RTD Location setting is equal to Off, the relay does not request that an
RTD Type setting be entered for that input.
The four available RTD types are:
• 100-ohm platinum (PT100)
• 100-ohm nickel (NI100)
• 120-ohm nickel (NI120)
• 10-ohm copper (CU10)
Th
e 825-P provides temperature warnings and trips using the RTD temperature
mea
surements and the warning and trip temperature settings in Table 27.
The relay issues a winding temperature warning if any of the healthy winding
RTDs (RTD Location setting equals WDG) indicate a temperature greater than
the corresponding RTD Warning Temperature setting. The relay issues a winding
temperature trip if one or two of the healthy winding RTDs indicate a
temperature greater than their RTD Trip Temperature settings. Two winding
RTDs must indicate excessive temperature when the Winding Trip Voting setting
equals Y. Only one excessive temperature indication is required if Winding Trip
Voting is not enabled. Bearing Trip Voting works similarly.
The warning and trip temperature settings for Bearing, Ambient, and Other
RTD types function similarly except that trip voting is not available for Ambient
and Other RTDs.
To disable a temperature warning or trip function, 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.
When you have connected an ambient temperature sensing RTD and set trip
temperatures for one or more winding RTDs, the relay gives you the option
to enable RTD Trip Temperature biasing by setting TMP RTD BIASING
equal to Y. The thermal model can also be biased by setting OL RTD BIASING
equal to Y (see Table 11) When you enable either of the biasing, the relay
does the following:
• C
alculates RTD % Thermal Capacity and adds the value to the Thermal
Met
er values.
• Automatically reduces the winding RTD Trip Temperatures if ambient
te
mperature rises above 40°C and TMP RTD BIASING is set equal to Y.
• A
utomatically reduces the Thermal Model element trip threshold if
ambien
t temperature rises above 40°C and OL RTD BIASING is set equal
to Y.
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