![background image](http://html1.mh-extra.com/html/abb/relion-670-series/relion-670-series_applications-manual_3052129361.webp)
Setting of zone 1
GUID-69E8535D-F3E2-483D-8463-089063712C67 v2
A voltage reversal can cause an artificial internal fault (voltage zero) on faulty line as well as on
the adjacent lines. This artificial fault always have a resistive component, this is however small
and can mostly not be used to prevent tripping of a healthy adjacent line.
An independent tripping zone 1 facing a bus which can be exposed to voltage reversal have to
be set with reduced reach with respect to this false fault. When the fault can move and pass
the bus, the zone 1 in this station must be blocked. Protection further out in the net must be
set with respect to this apparent fault as the protection at the bus.
Different settings of the reach for the zone (ZMFCPDIS) characteristic in forward and reverse
direction makes it possible to optimize the settings in order to maximize dependability and
security for independent zone1.
Due to the sub-harmonic oscillation swinging caused by the series capacitor at fault
conditions the reach of the under-reaching zone 1 must be further reduced. Zone 1 can only be
set with a percentage reach to the artificial fault according to the curve in
99000202.vsd
p
100
80
60
40
20
0
100 %
80
60
40
20
C
%
IEC99000202 V1 EN-US
Figure 235: Reduced reach due to the expected sub-harmonic oscillations at different
degrees of compensation
c
l
X
c degree of compensation
X
æ
ö
=
ç
÷
ç
÷
è
ø
EQUATION1894 V1 EN-US
(Equation 404)
X
c
is the reactance of the series capacitor
p is the maximum allowable reach for an under-reaching zone with respect to the sub-
harmonic swinging related to the resulting fundamental frequency reactance the zone is not
allowed to over-reach.
The degree of compensation C in figure
has to be interpreted as the relation between
series capacitor reactance X
C
and the total positive sequence reactance X1 to the driving
source to the fault. If only the line reactance is used the degree of compensation will be too
high and the zone 1 reach unnecessary reduced. The highest degree of compensation will occur
1MRK 505 343-UEN B
Section 7
Impedance protection
355
Application manual
Summary of Contents for Relion 670 series
Page 1: ...RELION 670 SERIES Line differential protection RED670 Version 2 1 IEC Application manual...
Page 2: ......
Page 40: ...34...
Page 64: ...58...
Page 150: ...144...
Page 406: ...400...
Page 472: ...466...
Page 494: ...488...
Page 512: ...506...
Page 524: ...518...
Page 604: ...598...
Page 686: ...680...
Page 718: ...712...
Page 722: ...716...
Page 758: ...752...
Page 759: ...753...