EQUATION356 V1 EN (Equation 46)
where:
Re designates the real component of current and voltage,
Im designates the imaginary component of current and voltage and
f
0
designates the rated system frequency
The algorithm calculates Rm measured resistance from the equation for the real value
of the voltage and substitute it in the equation for the imaginary part. The equation for
the Xm 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 47)
× - ×
= 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 48)
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.
6.5.2.5 Directional lines
The evaluation of the directionality takes place in the Directional impedance element
for mho characteristic ZDMRDIR (21D) function. Equation
49 is used to classify that
the fault is in forward direction for line-to-ground fault.
Section 6 1MRK505222-UUS C
Impedance protection
268
Technical reference manual
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