See the preprocessing function blocks in this document for the possible
signal sources.
Improper analog channel configuration causes a validation error if the analog
channels are not completely configured or they do not match with certain settings.
For troubleshooting, check the contents of this chapter and also the preprocessing
blocks in this document. The configuration can be written to the protection relay
once the mismatch is corrected.
4.1.10.5 Operation principle
The function can be enabled and disabled with the
Operation
setting. The
corresponding parameter values are "On" and "Off".
The operation of MPTTR can be described using a module diagram. All the modules
in the diagram are explained in the next sections.
The function uses ambient temperature which can be measured locally or remotely.
Local measurement is done by the protection relay. Remote measurement uses
analog GOOSE to connect AMB_TEMP input.
If the quality of remotely measured temperature is invalid or
communication channel fails the function uses ambient temperature set
in
Env temperature Set
.
Internal
FLC
calculator
Thermal
level
calculator
Alarm and
tripping
logic
ALARM
OPERATE
BLK_RESTART
START_EMERG
BLOCK
AMB_TEMP
I3P
I_B
Max
current
selector
I_A
TEMP_RL
I_C
I
2
Figure 238: Functional module diagram
Max current selector
Max current selector selects the highest measured TRMS phase current and reports
it to Thermal level calculator.
Internal FLC calculator
Full load current ( FLC) of the motor is defined by the manufacturer at an ambient
temperature of 40°C. Special considerations are required with an application where
the ambient temperature of a motor exceeds or remains below 40°C. A motor
operating at a higher temperature, even if at or below rated load, can subject the
motor windings to excessive temperature similar to that resulting from overload
operation at normal ambient temperature. The motor rating has to be appropriately
reduced for operation in such high ambient temperatures. Similarly, when the
ambient temperature is considerably lower than the nominal 40°C, the motor can
be slightly overloaded. For calculating thermal level it is better that the FLC values
1MRS759142 F
Protection functions
REX640
Technical Manual
411
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