Impact Of Series Compensation On Protective Ied Of Adjacent Lines - ABB RELION 670 Series Applications Manual

Section 7
Impedance protection
U
=
k
p
U
EQUATION1910 V1 EN-US
Where
U
MOV
U
NC
I
×
Kp In
IEC06000615 V1 EN-US
Figure 89: Equivalent impedance of MOV protected capacitor in dependence of
Figure 89
figure 87).
• Series capacitor prevails the scheme as long as the line current remains lower or equal to
its protective current level (I £ k
the complete reactance of a series capacitor.
• 50% of capacitor reactance appears in series with resistance, which corresponds to
approximately 36% of capacitor reactance when the line current equals two times the
protective current level (I £ 2· k
distance protection IED reach in resistive direction, for phase to earth fault measurement
as well as for phase to phase measurement.
• Series capacitor becomes nearly completely bridged by MOV when the line current
becomes higher than 10-times the protective current level (I £ 10· k
7.1.2.10

Impact of series compensation on protective IED of adjacent lines

Voltage inversion is not characteristic for the buses and IED points closest to the series
compensated line only. It can spread also deeper into the network and this way influences the
selection of protection devices (mostly distance IEDs) on remote ends of lines adjacent to the
series compensated circuit, and sometimes even deeper in the network.
172
MOV
NC
is the maximum instantaneous voltage expected between the capacitor immediately before the MOV
has conducted or during operation of the MOV, divaded by √2
is the rated voltage in RMS of the series capacitor
I
=
£ 2
1
×
Kp In
R R
protection factor K
presents three typical cases for series capacitor located at line end (case LOC=0% in
I
=
10
×
Kp In
R
en06000615.vsd
P
· I ). Line apparent impedance is in this case reduced for
p NC
· I ). This information has high importance for setting of
p NC
1MRK 504 152-UEN B
(Equation 74)
· I ).
p NC
SEMOD168320-318 v2
Application manual