Setting Of Zone 1; Setting Of Overreaching Zone - ABB RELION 650 Series Applications Manual

1MRK 505 363-UEN A
• Errors introduced by current and voltage instrument transformers, particularly under
transient conditions.
• Inaccuracies in the line zero-sequence impedance data, and their effect on the calculated
value of the earth-return compensation factor.
• The effect of infeed between the IED and the fault location, including the influence of
different Z
• The phase impedance of non transposed lines is not identical for all fault loops. The
difference between the impedances for different phase-to-earth loops can be as large as
5-10% of the total line impedance.
• The effect of a load transfer between the IEDs of the protected fault resistance is
considerable, the effect must be recognized.
• Zero-sequence mutual coupling from parallel lines.
7.1.3.2

Setting of zone 1

The different errors mentioned earlier usually require a limitation of the underreaching zone
(normally zone 1) to 75 - 90% of the protected line.
In case of parallel lines, consider the influence of the mutual coupling according to section
"Parallel line application with mutual coupling"
particular application. By proper setting it is possible to compensate for the cases when the
parallel line is in operation, out of service and not earthed and out of service and earthed in
both ends. The setting of earth-fault reach should be selected to be <95% also when parallel
line is out of service and earthed at both ends (worst case).
7.1.3.3

Setting of overreaching zone

The first overreaching zone (normally zone 2) must detect faults on the whole protected line.
Considering the different errors that might influence the measurement in the same way as for
zone 1, it is necessary to increase the reach of the overreaching zone to at least 120% of the
protected line. The zone 2 reach can be even higher if the fault infeed from adjacent lines at
remote end is considerable higher than the fault current at the IED location.
The setting shall generally not exceed 80% of the following impedances:
• The impedance corresponding to the protected line, plus the first zone reach of the
shortest adjacent line.
• The impedance corresponding to the protected line, plus the impedance of the maximum
number of transformers operating in parallel on the bus at the remote end of the
protected line.
Larger overreach than the mentioned 80% can often be acceptable due to fault current infeed
from other lines. This requires however analysis by means of fault calculations.
If any of the above gives a zone 2 reach less than 120%, the time delay of zone 2 must be
increased by approximately 200ms to avoid unwanted operation in cases when the
telecommunication for the short adjacent line at remote end is down during faults. The zone 2
must not be reduced below 120% of the protected line section. The whole line must be covered
under all conditions.
The requirement that the zone 2 shall not reach more than 80% of the shortest adjacent line at
remote end is highlighted in the example below.
If a fault occurs at point F see figure 64, the IED at point A senses the impedance:
Application manual
/Z ratios of the various sources.
0 1
and select the case(s) that are valid in the
Section 7
Impedance protection
GUID-ABD9A3B1-E420-471E-A798-4A56371E715E v1
GUID-8D7D4C9D-468B-465F-85D9-3D64500474DB v2
115