compensation at 50% of line length and 33% compensation located on 33% and 66%
of line length. The remote end compensation has the same effect.
• The voltage inversion occurs in cases when the capacitor reactance between the IED
point and fault appears bigger than the corresponding line reactance, Figure
89, 80%
compensation at local end. A voltage inversion occurs in IED point and the distance
IED will see wrong direction towards the fault, if no special measures have been
introduced in its design.
The situation differs when metal oxide varistors (MOV) are used for capacitor
overvoltage protection. MOVs conduct current, for the difference of spark gaps, only
when the instantaneous voltage drop over the capacitor becomes higher than the
protective voltage level in each half-cycle separately, see figure 90.
Extensive studies at Bonneville Power Administration in USA ( ref. Goldsworthy, D,L “A
Linearized Model for MOV-Protected series capacitors” Paper 86SM357–8 IEEE/PES
summer meeting in Mexico City July 1986) have resulted in construction of a non-linear
equivalent circuit with series connected capacitor and resistor. Their value depends on
complete line (fault) current and protection factor k
p
. The later is defined by equation
62.
ANSI13000293 V1 EN (Equation 366)
Where
V
MOV
is the maximum instantaneous voltage expected between the capacitor immediately before the MOV
has conducted or during operation of the MOV, divaded by √2
V
NC
is the rated voltage in RMS of the series capacitor
en06000615.vsd
R
j
X
1
I
£
R
j
X
2
I
=
R
j
X
10
I
=
Kp
×
In Kp
×
In
Kp
×
In
IEC06000615 V1 EN
Figure 209: Equivalent impedance of MOV protected capacitor in dependence of
protection factor K
P
Section 8 1MRK 506 369-UUS -
Impedance protection
410 Line distance protection REL670 2.2 ANSI
Application manual
To Next Page
Loading...
