often encountered during the motor start-up and with abnormal conditions such as
locked rotor or unbalance, which both produce excess heat due to the skin effect.
The skin effect causes the current to distribute in a smaller surface in the rotor bars,
increasing the resistance, and therefore also the heating effect.
The function also provides locked rotor protection. The locked rotor condition can
be identified from the slip estimate that the function calculates.
4.1.11.4 Analog channel configuration
RPTTR has two analog group inputs which must be properly configured.
Table 485: Analog inputs
Input Description
I3P Three-phase currents
U3P Three-phase voltages
4.1.11.5 Operation principle
The function can be enabled and disabled with the
Operation
setting. The
corresponding parameter values are "on" and "off".
The operation of RPTTR 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 IEC 61850-8-1 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
.
Alarm and
tripping
logic
ALARM
OPERATE
BLK_RESTART
STALL_IND
START_EMERG
BLOCK
AMB_TEMP
U3P
I3P
U_A
U_B
U_C
I_A
I_B
I_C
I
2
Rotor
resistance
calculator
Max
current
selector
InternalFLC
calculator
Thermal
level
calculator
TEMP_RL
Figure 245: RPTTR module diagram
Protection functions
1MRS759142 F
424 REX640
Technical Manual
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