2.5 Distance Protection
159
7SD5 Manual
C53000-G1176-C169-1
the parameters ZR(Z1) (address 1702) specifying the impedance of the upper zenith
of the MHO characteristic from the origin (reach), as well as the relevant delay time
settings.
For the first zone the delay times for single-phase and multiple-phase faults can be set
separately: T1-1phase (address 1605) and T1-multi-phase (address 1606). The
first zone is typically set to operate without additional time delay.
For the remaining zones the following correspondingly applies:
ZR(Z2) (address 1712);
ZR(Z3) (address 1722);
ZR(Z4) (address 1732);
ZR(Z5) (address 1742);
For the second zone it is also possible to set separate delay times for single- and multi-
phase faults. In general the delay times are set the same. If stability problems are ex-
pected during multiple-phase faults a shorter delay time can be considered for T2-
multi-phase (address 1616) while a higher setting for single phase faults may be
tolerated T2-1phase (address 1615).
The zone timers for the remaining zones are set with the parameters T3 DELAY (ad-
dress 1625), T4 DELAY (address 1635) and T5 DELAY (address 1645).
If the device is provided with the capability to trip single-pole, single-pole tripping is
then possible in the zones Z1 and Z2. While single-pole tripping usually applies to
single-phase faults in Z1 (if the remaining conditions for single-pole tripping are satis-
fied), this may also be selected for the second zone with address 1617 Trip 1pole
Z2. Single pole tripping in zone 2 is only possible if this address is set to Yes. The pre-
setting is No.
Note
For instantaneous tripping (undelayed) in the forward direction, the first zone Z1
should always be used, as only the Z1 and Z1B are guaranteed to trip with the shortest
operating time of the device. The further zones should be used sequentially for
grading in the forward direction.
If instantaneous tripping (undelayed) is required in the reverse direction, the zone Z3
should be used for this purpose, as only this zone ensures instantaneous pickup with
the shortest device operating time for faults in the reverse direction. This setting is also
recommended in teleprotection BLOCKING schemes.
With binary input indications 3619 „>BLOCK Z4 Ph-E“ and 3620 „>BLOCK Z5 Ph-
E“ zones Z4 and Z5 for phase-earth loops may be blocked. To block these zones per-
manently for phase-earth loops, said binary inputs must be set to the logic value of 1
via CFC.
Blocking of Zone Z1 If the main protection functions - differential protection and distance protection -
operate in parallel, the distance protection of Zone Z1 may pick up before the differen-
tial protection (e.g. in the case of close-up faults). If this is desired, the distance pro-
tection works as a „booster“ stage for fast tripping. If the fast tripping acts on one end
of the line only, accelerated tripping of zone Z1 is not desired (see also Section
2.5.1.4).
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