ABB RET670 Applications Manual page 249

1MRK504116-UUS C
Application manual
The increased reach related to the one used in non compensated system is
recommended for all protections in the vicinity of series capacitors to compensate for
delay in the operation caused by the sub harmonic swinging.
Settings of the resistive reaches are limited according to the minimum load impedance.
Reverse zone
The reverse zone that is normally used in the communication schemes for functions
like fault current reversal logic, weak-in-feed logic or issuing carrier send in blocking
scheme must detect all faults in the reverse direction which is detected in the opposite
IED by the overreaching zone 2. The maximum reach for the protection in the opposite
IED can be achieved with the series capacitor in operation.
The reactive reach can be set according to the following formula:
X1=1.3·X1 -0.5(X1
2Rem L
Settings of the resistive reaches are according to the minimum load impedance:
Optional higher distance protection zones
When some additional distance protection zones (zone 4, for example) are used they
must be set according to the influence of the series capacitor.
Setting of zones for parallel line application
Parallel line in service – Setting of zone1
With reference to section
reach can be set to 85% of protected line.
Parallel line in service – setting of zone2
Overreaching zones (in general, zones 2 and 3) must overreach the protected circuit in
all cases. The greatest reduction of a reach occurs in cases when both parallel circuits
are in service with a single phase-to-ground fault located at the end of a protected line.
The equivalent zero-sequence impedance circuit for this case is equal to the one in
figure 65 in section "Parallel line in
The components of the zero-sequence impedance for the overreaching zones must be
equal to at least:
R = R + R
0E 0 m0
EQUATION553 V1 EN
X = X + X
0E 0 m0
EQUATION554 V1 EN
-X )
C
"Parallel line application with mutual
service".
Section 3
IED application
coupling", the zone
(Equation 153)
(Equation 154)
243