Siemens SIPROTEC 7SJ531 - Page 78

-ETHOD OF OPERATION3*
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 %ARTH FAULT LOCATION
"Y MEANS OF THE DIRECTIONAL INDICATION OF THE NET
WORK THE EARTH
FAULTED LINE CAN OFTEN BE LOCATED )N
RADIAL NETWORKS LOCATION OF THE FAULTED LINE IS RELATIVE
LY SIMPLE 3INCE ALL CIRCUITS ON A BUSBAR &IGURE 
CARRY A CAPACITIVE PARTIAL CURRENT THE MEASURING
POINT ON THE FAULTED LINE IN AN ISOLATED NETWORK SEES
ALMOST THE ENTIRE PROSPECTIVE EARTH FAULT CURRENT OF
THE NETWORK IN COMPENSATED NETWORKS THE WATTMET
RIC RESIDUAL CURRENT FROM THE 0ETERSEN COIL FLOWS
THROUGH THE MEASURING POINT &OR THE FAULTED LINE OR
CABLE A DEFINITE
FORWARDS DECISION WILL RESULT
WHILST IN THE REMAINING CIRCUITS A
REVERSE INDICATION
WILL BE GIVEN UNLESS THE EARTH CURRENT IS SO SMALL THAT
NO MEASUREMENT CAN BE TAKEN )N ANY CASE THE
FAULTED CABLE CAN BE CLEARLY DETERMINED
)N MESHED OR RING NETWORKS THE MEASURING POINTS AT
THE ENDS OF THE FAULTED CABLE EQUALLY SEE A MAXIMUM
OF EARTH FAULT CAPACITIVE OR OHMIC CURRENT /NLY IN
THIS CABLE WILL THE DIRECTION
FORWARDS BE INDICATED
ON BOTH LINE ENDS &IGURE  %VEN THE REMAINING
DIRECTIONAL INDICATIONS IN THE NETWORK CAN AID LOCA
TION OF THE EARTH FAULT "UT UNDER CERTAIN CIRCUM
STANCES ONE OR MORE INDICATIONS MAY NOT BE GIVEN
DUE TO INSUFFICIENT EARTH CURRENT &URTHER ADVICE CAN
BE FOUND IN THE LEAFLET
%ARTH FAULT DETECTION IN ISO
LATED NEUTRAL OR ARC
SUPPRESSION COIL EARTHED HIGH
VOLTAGE SYSTEMS

&IGURE  &AULTED LINE LOCATION IN RADIAL NET
WORK
&IGURE  ,OCATION OF EARTH FAULT BASED ON THE DIRECTIONAL INDICATORS IN A MESHED NETWORK
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