The algorithm calculates R
m
measured resistance from the equation for the real value of
the voltage and substitutes it in the equation for the imaginary part. The equation for
the X
m
measured reactance can then be solved. The final result is equal to:
× D - × D
=
D × - D ×
m
Im (V) Re (I) Re (V) lm(I)
R
Re (I) lm(I) lm(I) Re (I)
EQUATION1550 V1 EN (Equation 60)
× - ×
= w
D × - D ×
× D ×
m 0
Re (V) lm(I) lm(V) Re (I)
X
Re (I) lm(I) lm(I) Re (I)
t
EQUATION1551 V1 EN (Equation 61)
The calculated R
m
and X
m
values are updated each sample and compared with the set
zone reach. The adaptive tripping counter counts the number of permissive tripping
results. This effectively removes any influence of errors introduced by the capacitive
voltage transformers or by other factors.
The directional evaluations are performed simultaneously in both forward and reverse
directions, and in all six fault loops. Positive sequence voltage and a phase locked
positive sequence memory voltage are used as a reference. This ensures unlimited
directional sensitivity for faults close to the IED point.
6.9.2.5 Directional impedance element for quadrilateral characteristics
The evaluation of the directionality takes place in Directional impedance quadrilateral
function ZDRDIR (21D). Equation 12 and equation 13 are used to classify that the
fault is in forward direction for phase-to-ground fault and phase-to-phase fault.
1 1
1
0.8 1 0.2 1
arg Re
L L M
L
V V
ArgDir ArgNeg s
I
× + ×
- < <
EQUATION1552 V2 EN (Equation 62)
For the AB element, the equation in forward direction is according to.
1MRK505222-UUS C Section 6
Impedance protection
313
Technical reference manual
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