ABB REU 610 Technical Reference Manual page 25

1MRS755769
Voltage Relay
Technical Reference Manual
The low- set undervoltage stage U< is based on conventional voltage
measurement. The low- set stage can also be used for alarm purposes.
The high- set undervoltage stage U<< can be set to be based on either:
Conventional voltage measurement ( U<< mode selected) or
*
Calculated positive phase- sequence voltage ( U
*
The selection between these modes is made either by using H M I or parameter
S7 , the default setting being conventional measurement. S tage U
U > ( N PS ) cannot be used at the same time.
2
The undervoltage stages can be set to be blocked when one of the measured
voltages fall below 0.15 × U
time. This feature can be used to avoid unnecessary starts and trips during, for
ex ample, an auto- reclose sequence. In addition, the tripping of stage U< can
be set to be blocked by the stage U<< start. The selection is made in S GF 4 .
S tage U<< can be set out of operation in S GF 3 / 2. This state is indicated by
dashes on the L CD and by 9 9 9 when the set start value is read via serial
communication.
It is possible to block the tripping of an undervoltage stage by
applying a digital input signal to the relay.
Un d er v oltage p r otec ti on
m eas u r em en t
Both the low- set and the high- set undervoltage stage can independently be set
to start and trip when one of the three voltages or all the voltages fall below
the set start value. By default, the low- set undervoltage stage operates when
one of the three voltages fall below the set start value and the high- set
undervoltage stage operates when all the voltages fall below the set start
value. The selection is made in S GF 4 / 7 and S GF 4 / 8 .
W hen the phase- to- phase voltage values fall below the set start value of the
low- set stage, U<, the stage generates a start signal after a ~ 8 0 ms' start time.
W hen the set operate time at definite- time characteristic or the calculated
operate time at ID M T characteristic elapses, the stage generates a trip signal.
S tage U< has a settable resetting time ( both at definite- time and ID M T
characteristics) , t <, for reset coordination with ex isting electromechanical
r
relays or for reducing fault clearance times of recurring, transient faults. If
stage U< has started and the phase- to- phase voltages ex ceed the set start
value of the stage, the start of the stage remains active for the set resetting
time. If the phase- to- phase voltages fall below the set start value again while
the timer is running, the timer is cleared and the start of the stage remains
active.
< mode selected) .
1
. The blocked stage is reset after the set resetting
n
b as ed on c on v en ti on al v oltage
REU 610
< ( PPS ) and
1
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