-ETHOD OF OPERATION3*
6
#
' #
/VERCURRENT TIME PROTECTION
4HE OVERCURRENT TIME PROTECTION CAN BE USED AS DEFI
NITE TIME OR INVERSE TIME OVERCURRENT PROTECTION
4HREE STANDARDIZED INVERSE TIME CHARACTERISTICS AC
CORDING TO )%#
OR EIGHT CHARACTERISTICS AC
CORDING TO !.3%)%%% AS WELL AS A FURTHER USER SPE
CIFIED CHARACTERISTIC ARE AVAILABLE FOR INVERSE TIME
MODE !N ADDITIONAL
LONG EARTH FAULT CHARACTERISTIC
IS AVAILABLE FOR EARTH CURRENT PROCESSING 4HE TRIP
TIME CHARACTERISTICS AND THE APPLIED FORMULAE ARE
GIVEN IN THE 4ECHNICAL DATA REFER TO &IGURES TO
3ECTIONS AND
4HE SELECTED OVERCURRENT TIME CHARACTERISTICS IS SU
PERIMPOSED BY A HIGH
SET INSTANTANEOUS OR DEFINITE
TIME DELAYED STAGE
4HE CHARACTERISTICS CAN BE INDIVIDUALLY SET FOR PHASE
CURRENTS AND FOR EARTH CURRENTS !LL STAGES ARE INDE
PENDENT FROM EACH OTHER AND CAN BE SET INDIVIDUALLY
5NDER CONDITIONS OF MANUAL CLOSING ONTO FAULT THE
OVERCURRENT TIME PROTECTION CAN ALSO PROVIDE A RAPID
TRIP ! CHOICE CAN BE MADE WHETHER THE ) STAGES
OR THE ))P STAGES ARE DECISIVE FOR AN UNDELAYED
TRIP IE THE ASSOCIATED TIME DELAY IS BY
PASSED FOR
THIS CONDITION
&ORMATION OF THE MEASURED
QUANTITIES
4HE MEASURED CURRENTS ARE FED TO THE RELAY VIA THE IN
PUT TRANSDUCERS FOR EACH PHASE 4HE INPUTS ARE GAL
VANICALLY ISOLATED AGAINST THE ELECTRONIC CIRCUITS AS
WELL AS AGAINST EACH OTHER 4HUS THE STAR POINT OF THE
THREE PHASE CURRENTS CAN BE FORMED OUTSIDE OF THE
RELAY OR FURTHER PROTECTION OR SUPERVISION DEVICES
CAN BE INCLUDED IN THE CURRENT TRANSFORMER CIRCUITS
&OR THE EARTH CURRENT INPUT EITHER THE RESIDUAL CUR
RENT OF THE PHASE CURRENT TRANSFORMERS MAY BE USED
OR A SEPARATE SUMMATION CURRENT TRANSFORMER MAY
BE CONNECTED
4HE SECONDARY SIDES OF THE RELAY INPUT TRANSFORMERS
ARE TERMINATED BY SHUNT RESISTORS WHICH TRANSFORM
THE CURRENTS TO PROPORTIONAL VOLTAGES THESE VOLTAGES
ARE CONVERTED TO NUMERICAL VALUES BY ANALOG
TO
DIGITAL CONVERTERS
$EFINITE TIME OVERCURRENT
PROTECTION
%ACH PHASE CURRENT IS COMPARED WITH THE LIMIT VALUE
WHICH IS SET IN COMMON FOR THE THREE PHASES 0ICK
UP IS INDICATED FOR EACH PHASE 4HE PHASE DEDICATED
TIMER IS STARTED !FTER THE TIME HAS ELAPSED TRIP SIGNAL
IS GIVEN 4HE PROTECTION CONTAINS TWO STAGES 4HE )
STAGE IS DELAYED WITH 4
) THE HIGH SET STAGE )
IS DELAYED WITH 4
)
4HE RESIDUAL EARTH CURRENT IS PROCESSED SEPARATELY
AND COMPARED WITH SEPARATE OVERCURRENT STAGES )
%
AND )
%
0ICK UP IS INDICATED !FTER THE ASSO
CIATED TIME 4
) OR 4 ) HAS ELAPSED TRIP COM
MAND IS GIVEN
4HE PICK
UP VALUES OF EACH STAGE ) PHASES )
%
EARTH ) PHASES AND )
%
EARTH AS WELL AS
THE ASSOCIATED TIME DELAYS CAN BE SET INDIVIDUALLY
4HE LOGIC DIAGRAM OF THE HIGH
CURRENT STAGE IS
SHOWN IN &IGURE THE LOGIC DIAGRAM OF THE DEFINITE
TIME OVERCURRENT PROTECTION STAGE IS SHOWN IN &IGURE
)NVERSE TIME OVERCURRENT PROTEC
TION
%ACH PHASE CURRENT IS COMPARED WITH THE LIMIT VALUE
WHICH IS SET IN COMMON FOR THE THREE PHASES 0ICK
UP IS INDICATED FOR EACH PHASE &OLLOWING PICK UP OF
THE INVERSE TIME STAGE )
P
THE TRIP TIME DELAY IS CALCU
LATED FROM THE SET INVERSE TIME CHARACTERISTIC AND THE
MAGNITUDE OF THE FAULT CURRENT !FTER THE TIME HAS
ELAPSED TRIP SIGNAL IS GIVEN &OR THE RESIDUAL EARTH
CURRENT A DIFFERENT CHARACTERISTIC CAN BE SELECTED
7HEN THE HIGH
SET OVERCURRENT STAGE ) PHASES
OR )
%
EARTH HAS PICKED UP THE ASSOCIATED TIMER
IS STARTED WHICH IS INDEPENDENT OF THE SET INVERSE
TIME CHARACTERISTIC FOR )
P
OR )
%P
!FTER THE ASSOCIATED
TIME 4
) OR 4 )% HAS ELAPSED TRIP COMMAND
IS GIVEN &IGURE IS VALID
4HE PICK
UP VALUES OF EACH STAGE )
P
PHASES )
%P
EARTH ) PHASES AND )
%
EARTH AS WELL AS
THE ASSOCIATED TIME FACTORS CAN BE SET INDIVIDUALLY
4HE LOGIC DIAGRAM OF THE INVERSE TIME OVERCURRENT
PROTECTION IS SHOWN IN &IGURE
&OR INVERSE TIME OVERCURRENT PROTECTION STAGES ONE
CAN SELECT WHETHER THE FUNDAMENTAL WAVE OF THE CUR
RENTS OR THE TRUE RMS VALUES ARE PROCESSED )F THE
FUNDAMENTAL WAVE IS SELECTED DC COMPONENTS AND
THE HARMONIC CONTENT IN THE CURRENTS ARE SUPPRESSED
AS THEY ARE FOR THE DEFINITE TIME OVERCURRENT PROTEC
TION STAGES
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