ABB Relion 670 series, Руководство по применению, Страница: 238 / 760

When Directional impedance element for mho characteristic (ZDMRDIR) is used
together with Fullscheme distance protection, mho characteristic (ZMHPDIS)
the following settings for parameter
DirEvalType in ZDMRDIR is vital:
• alternative
Comparator is strongly recommended
• alternative
Imp/Comp should generally not be used
• alternative Impedance should not be used. This alternative is intended for
use together with Distance protection zone, quadrilateral characteristic
(ZMQPDIS)
7.4.3.2 Setting of zone 1
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The zone 1 distance elements must be set to underreach a protected circuit to ensure external
fault security.
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
“Setting of zones for parallel line application” and select the case(s) / options that are valid in
the 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.
7.4.3.3 Setting of zone 2
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Zone 2 distance elements must be set according to the following criteria:
• Zone 2 should overreach all terminals of the protected circuit by an acceptable margin
(typically 20% of highest impedance seen) for all fault conditions and for all intended
modes of system operation
• As far as possible, zone 2 reach should be less than zone 1 coverage of all adjacent lines to
minimize the required zone 2 time delay setting.
It is necessary to consider the underreaching effects of zero sequence mutual coupling on
earth-fault impedance measurement when setting the reach of zone 2 distance protection to
meet the primary reach criterion for parallel circuits.
7.4.3.4 Setting of zone 3
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Zone 3 distance elements must be set according to the following criteria where possible:
• Zone 3 should overreach the remote terminal of the longest adjacent line by an acceptable
margin (typically 20% of highest impedance seen) for all fault conditions and in feed
conditions associated with all intended modes of system operation
• Zone 3 reach should be less than the zone 2 protection coverage of the shortest adjacent
transmission circuit, and it should not see through power transformers into distribution
systems in order to minimize the required zone 3 time delay setting.
7.4.3.5 Setting of overreaching zone
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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
Section 7 1MRK 505 343-UEN B
Impedance protection
232
Application manual