The setting values of all parameters that belong to ZMHPDIS must correspond to the
parameters of the protected line and be coordinated to the selectivity plan for the network.
Use different setting groups for the cases when the parallel line is in operation, out of
service and not grounded and out of service and grounded in both ends. In this way it is
possible to optimize the settings for each system condition.
When Directional impedance element for mho characteristic
(ZDMRDIR, 21D) 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)
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" and select the case(s) that are
valid in your application. We recommend to compensating the setting for the cases
when the parallel line is in operation, out of service and not grounded and out of
service and grounded in both ends. The setting of ground-fault reach should be selected
to be <95% also when parallel line is out of service and grounded at both ends (worst
case).
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:
1MRK504116-UUS C Section 3
IED application
275
Application manual
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