blocks in this document. The configuration can be written to the protection relay
once the mismatch is corrected.
4.10.5
Operation principle
The function can be enabled and disabled with the
Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of STTPMSU can be described with a module diagram. All the
modules in the diagram are explained in the next sections.
CB_CLOSED
Startup
supervisor
Thermal
stress
calculator
OPR_IIT
OPR_STALL
MOT_START
Stall
protection
STALL_IND
BLOCK
ST_EMERG_ENA
BLK_LK_ST
LOCK_START
I_A
I_B
I_C
Cumulative
startup
protection
I3P
Figure 614: Functional module diagram
Startup supervisor
This module detects the starting of the motor. The starting and stalling motor
conditions are detected in four different modes of operation. This is done through
the
Operation mode setting.
When the
Operation mode setting is operated in the "IIt" mode, the function
calculates the value of the thermal stress of the motor during the start-up
condition. In this mode, the start-up condition is detected by monitoring the TRMS
currents.
The
Operation mode setting in the "IIt, CB" mode enables the function to calculate
the value of the thermal stress when a start-up is monitored in addition to the
CB_CLOSED
input.
In the "IIt & stall" mode, the function calculates the thermal stress of the motor
during the start-up condition. The start-up condition is detected by monitoring the
TRMS currents.
In the "IIt & stall, CB" mode, the function calculates the thermal stress of the motor
during the start-up condition but the start-up condition is detected by monitoring
the TRMS current as well as the circuit breaker status.
In both the "IIt & stall" and "IIt & stall, CB" mode, the function also checks for motor
stalling by monitoring the speed switch.
1MRS759142 F
Protection functions
REX640
Technical Manual
1095