3.41
Date Code 20170601 Instruction Manual SEL-387-0, -5, -6 Relay
Differential, Restricted Earth Fault, Thermal, and Overcurrent Elements
Thermal Element (SEL-387-6 Relay)
Cooling Stage MVA Rating (MCSxy)
Range: 0.2–5000 MVA, in 0.1 MVA steps
The MVA rating for all types of transformers (XTYPE = 1 or 3) is taken as the
nameplate MVA (MVA) rating and the line-to-line kilovolt (kV) values.
Cooling Stage 2 (or 3) (CSxyS)
Range: SELOGIC control equation
The thermal element uses the output of SEL
OGIC control equations to
determine which cooling stage is active, so that thermal element calculations
use the correct transformer constants. The settings XTYPE and NCS
determine the number of SEL
OGIC control equations for which the relay will
prompt the user.
The CsxyS SEL
OGIC control equations can be set to any of the Relay Word
bits except rows 0 and 1 of Table 4.9. However, it is critical that they be
configured to accurately indicate which cooling system is active. In the
simplest implementation, this will consist of one or two external contacts from
the monitored power transformer connected to optoisolated inputs on the
SEL-387 with the CsxyS SEL
OGIC control equations set to the corresponding
digital input.
Default Ambient Temperature (DTMP)
Range: –40 to 85°C, in 1°C steps
Select a reasonable value for DTMP, even if your data acquisition system
provides measurement of the ambient temperature (near the power
transformer). In this case the thermal element calculations will use the DTMP
setting, should the ambient temperature input not function on relay power up.
If your data acquisition system cannot measure ambient temperature, then the
thermal element calculations always use the DTMP value. The DTMP setting
units are degrees Celsius.
Table 3.2 Examples of Cooling Stages and MVA Ratings
XTYPE = 3
Cooling Stage MVA Rating
CS1 (oil and air cooled) MCS11 = 100
CS2 (forced air cooled) MCS12 = 140
CS3 (forced oil and air cooled) MCS13 = 170
XTYPE = 1
Cooling System MVA Rating
Transformer 1 Transformer 2 Transformer 3
CS1 (oil and air cooled) MCS11 = 100 MCS21 = 100 MCS31 = 100
CS2 (forced air cooled) MCS12 = 140 MCS22 = 140 MCS32 = 140
CS3 (forced oil and air cooled) MCS13 = 170 MCS23 = 170 MCS33 = 170
NOTE: x designates the transformer
and y designates the cooling stage.
NOTE: x designates the transformer
and y designates the cooling stage.
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