Here IN is a phasor of the residual current in IED point. This results in the same reach
along the line for all types of faults.
The apparent impedance is considered as an impedance loop with resistance R and
reactance X.
The formula given in equation
42 is only valid for no loaded radial feeder applications.
When load is considered in the case of single line-to-ground fault, conventional
distance protection might overreach at exporting end and underreach at importing end.
IED has an adaptive load compensation which increases the security in such applications.
Measuring elements receive current and voltage information from the A/D converter.
The check sums are calculated and compared, and the information is distributed into
memory locations. For each of the six supervised fault loops, sampled values of
voltage (V), current (I), and changes in current between samples (DI) are brought from
the input memory and fed to a recursive Fourier filter.
The filter provides two orthogonal values for each input. These values are related to the
loop impedance according to equation 43,
EQUATION1547 V1 EN (Equation 43)
in complex notation, or:
0
Re ( )
Re ( ) Re ( )
X I
V R I
t
D
= × + ×
w D
EQUATION1548 V1 EN
(Equation 44)
0
Im ( )
Im ( ) Im ( )
X I
V R I
t
D
= × + ×
w D
EQUATION1549 V1 EN (Equation 45)
with
1MRK505222-UUS C Section 6
Impedance protection
267
Technical reference manual
To Next Page
Loading...
