-ETHOD OF OPERATION3*
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-EASURING
ELEMENT
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CURRENT VOLTAGE
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CURRENT VOLTAGE CURRENT VOLTAGE CURRENT VOLTAGE
4ABLE -EASURED VALUES FOR DIRECTIONAL DETERMINATION
4HE THEORETICAL DIRECTIONAL LINE IS SHOWN IN &IGURE
IN THE COMPLEX 2
8 DIAGRAM SOLID LINE A )N
PRACTICE THE POSITION OF THE DIRECTIONAL CHARACTERISTIC
IS DEPENDENT UPON THE SOURCE IMPEDANCE AS WELL AS
THE LOAD CURRENT CARRIED BY THE LINE IMMEDIATELY BE
FORE FAULT INCEPTION
3INCE THE UNFAULTED VOLTAGE IS INFLUENCED BY THE
MAGNITUDE OF THE FAULT VOLTAGE FOR TWO
PHASE FAULTS
REFER ALSO TO &IGURE B THE ACTUAL DIRECTIONAL
CHARACTERISTIC MAY DIFFER FROM THE THEORETICAL CHARAC
TERISTIC 7HEN FOR EXAMPLE A TWO
PHASE FAULT
,
, HAS OCCURRED THE DIRECTIONAL CHARACTERISTIC OF
THE MEASURING ELEMENT , APPEARS TO BE DISPLACED
IN MATHEMATICALLY POSITIVE SENSE BROKEN LINE B IN
&IGURE WHEREAS THE THE DIRECTIONAL CHARACTERIS
TIC OF THE MEASURING ELEMENT , APPEARS TO BE DIS
PLACED IN MATHEMATICALLY NEGATIVE SENSE BROKEN
LINE C IN &IGURE )N PRACTICE THIS IS IRRELEVANT BE
CAUSE THE FAULT IMPEDANCE VECTOR CAN BE LOCATED
ONLY IN THE FIRST OR THIRD QUADRANT OF THE COMPLEX
PLANE
DIRECTIONAL
CHARACTERISTIC
J8
: FORWARDS
CAPACITIVE
INDUCTIVE
REVERSE
2
A
B
C
&AULT IMPEDANCE VECTOR
&IGURE $IRECTIONAL CHARACTERISTICS
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