Siemens SIPROTEC 7SJ531 - Page 74

-ETHOD OF OPERATION3*
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5PH MIN
ANNUNCIATION
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4RIP
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 MEAS
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 CALCUL
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&UNCTION NUMBER
%& $ETECTION
%& $ETEC ,
%& $ETEC ,
5% 4RIP
5% &AULT
%& $ETEC ,
BLOCK TRIP STAGE
EARTH FAULT DETECTION
ALARM ONLY
BLOCK EARTH FAULT
DETECTION
EARTH FAULT DETECTION
OFF
EARTH FAULT DETECTION
ON
5% BLOCK
%& ANNUNC
%& $ETBLOC
%& $ET OFF
5E
RELEASE
ACC
&IG 
&IGURE  ,OGIC DIAGRAM OF THE VOLTAGE STAGES OF EARTH FAULT PROTECTION
 (IGHLY SENSITIVE EARTH CURRENT
STAGES


4HE MAGNITUDE OF THE EARTH CURRENT IS DECISIVE FOR
PICK
UP OF THE HIGHLY SENSITIVE EARTH CURRENT STAGES
4HEY ARE USED IN CASES WHERE THE MAGNITUDE OF THE
EARTH CURRENT IS THE MAIN CRITERION OF THE EARTH FAULT
THEREFORE PREFERABLY IN SOLIDLY EARTHED OR LOW
IMPE
DANCE EARTHED SYSTEMS OR FOR ELECTRICAL MACHINES IN
BUS
BAR CONNECTION WITH ISOLATED SYSTEMS WHERE
THE HIGH CAPACITIVE CURRENT OF THE SYSTEM CAN BE EX
PECTED IN CASE OF MACHINE EARTH FAULT BUT ONLY AN IN
SIGNIFICANT EARTH CURRENT IN CASE OF A SYSTEM EARTH
FAULT BECAUSE OF THE LOW MACHINE CAPACITANCE
)N ORDER TO DETECT EARTH CURRENTS A TWO
STAGE CUR
RENT TIME CHARACTERISTIC CAN BE SET %ACH STAGE CAN
OPERATE DIRECTIONAL OR NON
DIRECTIONAL

 ONLY FOR MODEL 3*J JJJJ JJJJ
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