ABB RELION 670 Series Product Manual page 30

Transformer protection RET670 2.1 IEC
The heavy load transfer that is common in many
transmission networks may make fault resistance
coverage difficult to achieve. Therefore, the function has
a built in algorithm for load encroachment, which gives
the possibility to enlarge the resistive setting of both
the phase selection and the measuring zones without
interfering with the load.
The extensive output signals from the phase selection
gives also important information about faulty phase(s)
which can be used for fault analysis.
A current-based phase selection is also included. The
measuring elements continuously measure three phase
currents and the residual current and, compare them
with the set values.
High speed distance protection, quadrilateral and
mho ZMFPDIS
The high speed distance protection (ZMFPDIS) provides
a sub-cycle, down towards a half-cycle operate time. Its
six zone, full scheme protection concept is entirely
suitable in applications with single-phase autoreclosing.
Each measurement zone is designed with the flexibility
to operate in either quadrilateral or mho characteristic
mode. This can even be decided separate for the phase-
to-ground or phase-to-phase loops. The six zones can
operate either independent of each other, or their start
can be linked (per zone) through the phase selector or
the first starting zone. This can provide fast operate
times for evolving faults.
The operation of the phase-selection is primarily based
on a current change criteria (i.e. delta quantities),
however there is also a phase selection criterion
operating in parallel which bases its operation on
voltage and current phasors exclusively. Additionally the
directional element provides a fast and correct
directional decision under difficult operating conditions,
including close-in three-phase faults, simultaneous
faults and faults with only zero-sequence in-feed.During
phase-to-earth faults on heavily loaded power lines
there is an adaptive load compensation algorithm that
prevents overreaching of the distance zones in the load
exporting end, improving the selectivity of the function.
This also reduces underreach in the importing end.
Distance zones quad with high speed distance for
series compensated networks ZMFCPDIS
The high speed distance protection (ZMFCPDIS)
provides a sub-cycle, down towards a half-cycle operate
time. Its six zone, full scheme protection concept is
entirely suitable in applications with single-phase
autoreclosing.
High speed distance protection ZMFCPDIS is
fundamentally the same function as ZMFPDIS but
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provides more flexibility in zone settings to suit more
complex applications, such as series compensated lines.
In operation for series compensated networks, the
parameters of the directional function are altered to
handle voltage reversal.
Each measurement zone is designed with the flexibility
to operate in either quadrilateral or mho characteristic
mode. This can even be decided separate for the phase-
to-ground or phase-to-phase loops. The six zones can
operate either independent of each other, or their start
can be linked (per zone) through the phase selector or
the first starting zone. This can provide fast operate
times for evolving faults.
The operation of the phase-selection is primarily based
on a current change criteria (i.e. delta quantities),
however there is also a phase selection criterion
operating in parallel which bases its operation on
voltage and current phasors exclusively. Additionally the
directional element provides a fast and correct
directional decision under difficult operating conditions,
including close-in three-phase faults, simultaneous
faults and faults with only zero-sequence in-feed.
During phase-to-earth faults on heavily loaded power
lines there is an adaptive load compensation algorithm
that prevents overreaching of the distance zones in the
load exporting end, improving the selectivity of the
function. This also reduces underreach in the importing
end.
Power swing detection ZMRPSB
Power swings may occur after disconnection of heavy
loads or trip of big generation plants.
Power swing detection function ZMRPSB is used to
detect power swings and initiate block of all distance
protection zones. Occurrence of earth-fault currents
during a power swing inhibits the ZMRPSB function, to
allow fault clearance.
Power swing logic PSLPSCH
Power Swing Logic (PSLPSCH) is a complementary
function to Power Swing Detection (ZMRPSB) function.
It provides possibility for selective tripping of faults on
power lines during system oscillations (power swings or
pole slips), when the distance protection function
should normally be blocked. The complete logic consists
of two different parts:
• Communication and tripping part: provides selective
tripping on the basis of special distance protection
zones and a scheme communication logic, which are
not blocked during the system oscillations.
• Blocking part: blocks unwanted operation of
instantaneous distance protection zone 1 for
oscillations, which are initiated by faults and their
1MRK 504 155-BEN F
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SEMOD131350-4 v4
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