EQUATION356 V1 EN (Equation 19)
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 20)
× - ×
= 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 21)
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.
6.2.2.5 Directionality for series compensation
In the basic distance protection function, the control of the memory for polarizing
voltage is performed by an under voltage control. In case of series compensated line, a
voltage reversal can occur with a relatively high voltage also when the memory must
be locked. Thus, a simple undervoltage type of voltage memory control can not be used
in case of voltage reversal. In the option for series compensated network the polarizing
quantity and memory are controlled by an impedance measurement criterion.
Section 6 1MRK505222-UUS C
Impedance protection
204
Technical reference manual
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