Siemens SIPROTEC 7SJ531 - Page 62

-ETHOD OF OPERATION3*
6
#
' #

2ESET THRESHOLD 
R|5|53#
0ICK
UP THRESHOLD
4HRESHOLD FOR
START
UP CRITERION
5
N
5
RMS
T
T
)
RMS
T
)
N
5 RESET
5 3#
5
3# )
T
T
4RIP
COMMAND
#,/3%
COMMAND
0ICK
UP
5
$ROP OFF
5
4 5
4RIP
4 3#
2ECLOSURE
LOCKED
0ICK UP
&IGURE  4YPICAL FAULT SEQUENCE WITH VOLTAGE TRANSFORMERS INSTALLED AT THE BUS BAR SIDE
4HE GENERAL CURRENT CRITERION ## MENTIONED UNDER
 APPLIES EQUALLY TO BOTH UNDERVOLTAGE STAGES
7ITH AN ACTIVATED CURRENT CRITERION THE PROTECTION
PICKS UP ONLY WHEN TOGETHER WITH THE UNDERVOLTAGE
CONDITION ALSO THE RELEASE CONDITION OF THE CURRENT
CRITERION ## IS FULFILLED 4HIS ALSO MEANS THAT FOR UN
DERVOLTAGE WITHOUT RELEASE FROM THE CURRENT CRITERION
THE PROTECTION PICK
UP RESETS
)N ORDER TO AVOID MALOPERATION IN CASE OF A SECOND
ARY VOLTAGE FAILURE EG BY OPERATION OF THE VOLTAGE
TRANSFORMER MINIATURE CIRCUIT BREAKER THE PROTEC
TION CAN BE BLOCKED VIA A BINARY INPUT FOR BOTH UNDER
VOLTAGE STAGES TOGETHER OR SEPARATELY FOR 5 AND
5 VIA TWO BINARY INPUTS 7HEN BLOCKING BE
COMES EFFECTIVE DURING A PICK
UP CONDITION THE
PICK
UP RESETS AS WELL AS THE STARTED DELAY TIMES
ARE RESET TOO
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