-ETHOD OF OPERATION
3$
6
# ' #
#ONNECTION FOR DECREASED EARTH
CURRENT SENSITIVITY , , ,
)N EARTHED SYSTEMS WITH PARTICULARLY LOW ZERO SE
QUENCE IMPEDANCE EARTH FAULT CURRENTS CAN BE LARG
ER THAN THOSE UNDER TWO PHASE FAULT CONDITIONS 7ITH
CONSIDERATION OF THE THERMAL LOADING ON THE MEASUR
ING CIRCUITS THE CONNECTIONS SHOWN IN &IGURE CAN
BE USED 7ITH THIS CONNECTION THE VALUES GIVEN IN
4ABLE CAN BE RECALCULATED FOR THE SEVEN POSSIBLE
FAULT CONDITIONS IN SOLIDLY EARTHED NETWORKS
#OMPARISON WITH 4ABLE SHOWS THAT UNDER EARTH
FAULT CONDITIONS THE WEIGHTING FACTOR 7 IS LESS THAN
WITH THE STANDARD CONNECTION 4HUS THE THERMAL
LOADING IS REDUCED TO IE
-4
, , ,
3$
)
,
)
,
)
,
I
-
&IGURE
#ONNECTION , , , WITH DE
CREASED EARTH CURRENT SENSITIVITY
I
,
I
,
I
,
|
I
,
|
I
,
I
-
I
-
I
,
I
,
I
,
o
|
\
I
\
I
,
&IGURE
!DDITION OF CURRENTS IN THE SUMMATION TRANSFORMER WITH CT CONNECTION , , ,
o
, , , SYM
&AULT TYPE
7
7
o
, ,
, ,
, ,
, %
, %
, %
X )
.
X )
.
X )
.
X )
X )
.
.
X )
.
X )
.
)
FOR I
-
M!
4ABLE
4YPES OF FAULT AND WEIGHTING FACTOR WITH CT CONNECTION , , ,
Summary of Contents for 7SD502
Page 148: ... PPENDIX 3 6 PPENDIX ENERAL DIAGRAMS ONNECTION DIAGRAMS 4ABLES ...
Page 176: ... 3 6 ...
