-ETHOD OF OPERATION
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&IGURE 4HREE SYSTEM PROTECTION ONE DIFFER
ENTIAL PROTECTION RELAY FOR EACH OF THE
PHASES
! FURTHER POSSIBLE ARRANGEMENT IS GIVEN BY COMBIN
ING THE &IGURE CONNECTION WITH A SECOND DIFFEREN
TIAL RELAY WHICH IS CONNECTED ONLY IN THE STAR POINT OF
THE THREE CTS &IGURE !LTHOUGH THIS ARRANGE
MENT REQUIRES TWO DIFFERENTIAL RELAYS IT HAS THE ADVAN
TAGE THAT THE SECOND RELAY IS LIMITED TO THE DETECTION
OF EARTH FAULTS AND WHEN NECESSARY CAN BE MADE TO
BE VERY SENSITIVE IN THE ILLUSTRATED EXAMPLE
o
4HIS SYSTEM IS USED ONLY IN EARTHED NETWORKS
)T IS OF COURSE ALSO POSSIBLE TO USE FOUR DIFFERENTIAL
PROTECTION SCHEMES FOR ONE LINE ONE FOR EACH OF THE
PHASES AND A FURTHER FOR THE RESIDUAL CURRENT PATH
IE TO COMBINE &IGURE AND
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&IGURE 3EPARATE EARTH FAULT RELAY
Содержание 7SD502
Страница 148: ... PPENDIX 3 6 PPENDIX ENERAL DIAGRAMS ONNECTION DIAGRAMS 4ABLES ...
Страница 176: ... 3 6 ...