Zero-sequence compensation of double-circuit lines
The magnitude and phase-angle of the zero-sequence compensation factor for a double-
circuit line are set using parameters
k0m and k0mAng. This compensation only applies to
Zones 1 and 2, the overreaching zone and the reverse zone.
Directional unit
Each distance zone has its own directional measuring unit. The voltage used for measurement
depends on the amplitude of the fault voltage in relation to the parameter
UminFault. The
fault voltage is used, providing it is higher than the setting of
UminFault and a voltage derived
from the healthy voltage and the memory voltage is used when it falls below. The
recommended settings are 0.1 UN for conventional VTs.
Should correct determination of direction not be possible (reference voltage too low or
memory voltage decayed), the setting of the parameter
MemDirMode determines whether the
protection blocks or trips:
•
Block — Protection blocks all zones (definitive zone only if directional)
•
Trip — Protection trips
•
Cond. trip — Protection blocks unless the instantaneous and preceding zones are in
opposite directions, in which case the protection trips.
Overreaching zone (OR)
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The settings including the designation 4/OR (X (4/OR) delay (4/OR)) can be used either for a
fourth measuring zone or a completely independent overreaching zone (but not for both at the
same time) by appropriately setting the parameter
Delay (4/OR).
In applications requiring a fourth zone, the measuring unit of the second zone is used for
overreaching. An overreaching zone is necessary for the switch-onto-fault and zone extension
logics and for overreaching transfer tripping schemes.
Reverse zone (BACK)
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A reverse measuring zone is used in a blocking scheme and also the logic for detecting a
reversal of fault energy direction. It is set using the parameters
X (BACK), R (BACK), RR (BACK)
and
RRE (BACK) which have setting ranges from 0 to 300 Ω/ph.
Note that:
•
for underimpedance starting (UZ):
With the exception of the load discrimination defined by the parameters
RLoad and
AngleLoad, the reverse zone operates independently of the starters.
•
for overcurrent starting (OC):
The reverse zone is only in operation when an overcurrent starter (
IStart) has picked up.
•
The binary input (Ext Blk UZ) blocks operation regardless of the starter mode for the
reverse zone.
•
Signal output: Meas Bward
•
Measurement of the reverse zone only takes place while the first zone is active, that is, the
Meas Bward signal resets at the latest at the end the second time step.
Time steps (Delay)
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The operating time of every activated distance zone (parameter
X <> 0) is determined by the
parameter
Delay, which has a setting range of 0 to 10 s in steps of 0.01. The parameter Delay
(4/OR) is also associated with a logic, which determines whether it applies to Zone 4 or to the
overreaching zone, that is, if Delay (4/OR) < Delay (2), it applies to the overreaching zone,
otherwise to Zone 4.
The set times must satisfy the following relationships:
Section 5
1MRK 505 406-UEN B
Bay protection functions
46
Bay protection functions REB500
Technical manual
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