-ETHOD OF OPERATION
3$
6
# ' #
#URRENT TRANSFORMER CONNECTIONS AND FAULT CURRENT SENSITIVITY
4HE CURRENTS FROM THE PROTECTED LINE ARE MIXED IN THE
SUMMATION TRANSFORMER -4 OF THE 3$ RELAY TO A
SINGLEPHASE ALTERNATING CURRENT OF M! AT RATED
SYMMETRICAL CURRENT 4HE ASYMMETRICAL RATIO OF THE
MIXED CURRENT OF ENSURES THAT WITH ANY KIND OF
FAULT A DEFINED MIXED CURRENT IS PRODUCED WHICH IS
RELEVANT FOR ALL PROTECTION FUNCTIONS 4HE ASYMMETRY
ENTAILS
ON THE OTHER HAND
THAT THE SENSITIVITY OF
THE PROTECTION FUNCTIONS IS DIFFERENT AND DEPENDS ON
THE KIND OF FAULT "UT THIS IS OF LESS IMPORTANCE IN THE
FIELD OF APPLICATION OF THIS RELAY SINCE THE PHASEFAULT
CURRENTS NORMALLY EXCEED CLEARLY THE RATED CURRENT
$IFFERENT OPTIONS ARE AVAILABLE FOR THE CONNECTION OF
THE CURRENT TRANSFORMERS "UT THE SAME CT CONNEC
TION METHOD SHOULD BE USED THROUGHOUT A NETWORK
AND MUST BE USED AT OPPOSITE LINE ENDS OF A DIFFEREN
TIAL PROTECTION SCHEME
3TANDARD CONNECTION , , %
4HE SCHEME SHOWN IN &IGURE IS THE MOST COM
MON 4HE INPUT WINDINGS OF THE SUMMATION TRANS
FORMER ARE CONNECTED TO THE CT CURRENTS )
,
)
,
AND
)
%
RESIDUAL CURRENT 4HIS CONNECTION IS SUITABLE FOR
ALL KINDS OF SYSTEMS REGARDLESS OF THE TREATMENT OF
THE SYSTEM NEUTRAL )T IS CHARACTERIZED BY A HIGH SEN
SITIVITY FOR EARTH FAULTS
-4
, , ,
3$
)
,
)
,
)
%
I
-
&IGURE
3TANDARD CT CONNECTION , , %
&OR A SYMMETRICAL THREEPHASE FAULT WHERE THE EARTH
RETURN COMPONENT )
%
THE SINGLEPHASE MIXED
CURRENT IS AS ILLUSTRATED IN &IGURE
o
TIMES THE
WINDING UNIT VALUE 4HAT IS THE SUMMATION FLUX AM
PERE TURNS IS THE SAME AS IT WOULD BE FOR SINGLE
PHASE CURRENT
o
TIMES THE VALUE FLOWING THROUGH
THE WINDING WITH THE LEAST NUMBER OF TURNS RATIO
&OR THREEPHASE SYMMETRICAL FAULT CURRENT EQUAL TO
RATED CURRENT )
.
THE SECONDARY SINGLEPHASE CURRENT
IS I
-
M! !LL RELAY CHARACTERISTIC OPERATING VAL
UES ARE BASED ON THIS TYPE OF FAULT AND THESE CUR
RENTS
I
,
I
,
I
,
|
I
,
I
,
I
-
I
-
I
,
I
,
o
|
\
I
\
&IGURE
3UMMATION OF CURRENTS IN THE SUMMATION TRANSFORMER WITH STANDARD CT CONNECTION
, , %
Summary of Contents for 7SD502
Page 148: ... PPENDIX 3 6 PPENDIX ENERAL DIAGRAMS ONNECTION DIAGRAMS 4ABLES ...
Page 176: ... 3 6 ...