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1MRS751802-MUM
Protection Relay
Technical Reference Manual, Standard Configurations
REX 521
3U<<
Three-phase undervoltage protection, high-set stage
3I2f>
Three-phase transformer inrush and motor start-up current detector
Iub>
Phase discontinuity protection
3Ith>
Three-phase thermal protection for cables
3Ithdev
Three-phase thermal overload protection for devices
O->I
Auto-reclose function (5 shots)
Uo>
Residual overvoltage protection, low-set stage
Uo>>
Residual overvoltage protection, high-set stage
Uo>>>
Residual overvoltage protection, instantaneous stage
U1<U1U2>
Phase sequence voltage protection
f1
Underfrequency or overfrequency protection, stage 1
f2
Underfrequency or overfrequency protection, stage 2
FUSEF
Fuse failure protection
SYNC1
Synchro-check / voltage-check function
Table 2.-3 Control functions available in the different standard configurations
of REX 521
Function
Description
I<->O CB1
Circuit breaker control with indication
I<->O IND1
Object indication
I<->O IND2
Object indication
I<->O IND3
Object indication
I<->O POS
Logic control position selector
ALARM1-8
Alarm LED 1-8
Table 2.-4 Measurement functions available in the different standard
configurations of REX 521
Function Description
3I
Three-phase current measurement
Io
Neutral current measurement
Uo
Residual voltage measurement
DREC
Transient disturbance recorder
3U
Three-phase voltage measurement
3U_B
Three-phase voltage measurement
f
System frequency measurement
PQE
Three-phase power and energy measurement
MEAI1
Analog measuring function
Table 2.-2 Protection functions available in the different standard
configurations of REX 521
Function
Description
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