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setting of
IPh< and UPh<. The choice of UlLevel gives a faster and more sensitive operation of
the function, which is important for reducing the stress that might occur when energizing
onto a fault. However, the voltage recovery can be slow in some systems when energizing the
line. Therefore, if the timer
tDuration is set too short, ZCVPSOF can interpret this as a fault
and release a trip.
When
Mode is set to Impedance, the operate criterion is based on the
BC
input (breaker
closing), which can be the start of the overreaching zone from the impedance zone
measurement or a
tOperate-delayed
START_DLYD
input. A nondirectional output signal should
be used from an overreaching zone. The selection of the
Impedance mode gives increased
security.
When
Mode is set to UlLvl&Imp, the condition for tripping is an ORed between UlLevel and
Impedance.
tDuration: The setting of the timer for the release of UlLevel is, by default, 0.02 seconds, which
has proven to be suitable in most cases from field experience. If a shorter time delay is to be
set, it is necessary to consider the voltage recovery time during line energization.
tOperate: The time delay for the
START_DLYD
input to activate
TRIP
when
Mode is set to
Impedance or UlLvl&Imp is, by default, set to 0.03 seconds.
7.19
Phase preference logic PPLPHIZ
SEMOD151920-1 v2
7.19.1
Identification
SEMOD151937-2 v2
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Phase preference logic
PPLPHIZ
-
-
7.19.2
Application
SEMOD167856-4 v5
Phase preference logic function PPLPHIZ is an auxiliary function to Distance protection zone,
quadrilateral characteristic ZMQPDIS and Phase selection with load encroachment,
quadrilateral characteristic function FDPSPDIS. The purpose is to create the logic in resonance
or high resistive earthed systems (normally sub-transmission) to achieve the correct phase
selective tripping during two simultaneous single-phase earth-faults in different phases on
different line sections.
Due to the resonance/high resistive earthing principle, the earth faults in the system gives
very low fault currents, typically below 25 A. At the same time, the occurring system voltages
on the healthy phases will increase to line voltage level as the neutral displacement is equal to
the phase voltage level at a fully developed earth fault. This increase of the healthy phase
voltage, together with slow tripping, gives a considerable increase of the risk of a second fault
in a healthy phase and the second fault can occur at any location. When it occurs on another
feeder, the fault is commonly called cross-country fault.
Different practices for tripping is used by different utilities. The main use of this logic is in
systems where single phase-to-earth faults are not automatically cleared, only alarm is given
and the fault is left on until a suitable time to send people to track down and repair the fault.
When cross-country faults occur, the practice is to trip only one of the faulty lines. In other
cases, a sensitive, directional earth-fault protection is provided to trip, but due to the low fault
currents long tripping times are utilized.
Section 7
1MRK 505 343-UEN B
Impedance protection
396
Application manual
Summary of Contents for Relion 670 series
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