ABB RER670 Applications Manual page 117

1MRK 506 375-UEN A
Railway application RER670 2.2 IEC
Application manual
tI0: Delay time for the residual overcurrent start. Residual overcurrent start is
delayed by settable time delay tI0. The default setting is 0.2s.
If magnitude of the phase L1 current is more than KI times magnitude of phase L2
current together with delayed residual overcurrent start signal and ModePhSelKI is
set to Off, the L1E loop will be released for distance measuring. This is valid for
phase L2 as well.
Phase selection based on residual overcurrent start is done only if the stub mode is
not selected. This means that the setting ModeStubline is set to Off and there are no
outputs from the underimpedance starting loops.
I01: This setting is used to detect the high short circuit current during the blocking
time tI01 when starting element impedance loop has picked up. A default setting of
300% IB is used.
tI01: This is used as the blocking time of distance measuring for the transient earth
fault. A default setting of 0.1s is used.
The underimpedance start and residual overcurrent start operates in the event of an
earth fault. Once the earth fault is detected, it is blocked for a set time delay tI01 to
avoid tripping in any of the transient earth fault conditions. However, if the
measured current in a phase exceeds the set value I01 and the respective
underimpedance loop has also picked up, the distance measuring loop of that loop
is released immediately. This is done in order to clear the high current faults
instantaneously. Phase-to-phase fault loop is released if there is output from the
under impedance starting and there is no residual overcurrent start output.
I0MinPhSel: This is the minimum current that should be present to detect a phase-
to-phase fault. The recommended setting is 4.0% IB.
ModeI0StRel: This is used to release the L1E & L2E / L1L2 distance measuring
loops using the residual overcurrent start. The default setting is L1E & L2E.
If magnitudes of both phase currents (IL1 and IL2) are almost equal or less than the
set value I0MinPhSel, it indicates that a phase-to-phase fault has occurred in the
system. At this condition, the measuring loops are enabled based on the setting
mode ModeI0StRel and the respective loops will be released for distance
measuring.
Phase preference
The time steps from t0L2 to t6L2 listed below can be selected by
settings OpModet0L2 to OpModet6L2 for stub line and each
distance zone 1 to zone 6 respectively.
For faults on phase L2, after distance and direction decision is fulfilled, an alarm
will appear and the additional timers t1L2 to t6L2 will start. If the starting element
is reset before the expiry of (and therefore before trip) the zone timers tPEZx plus
Section 7
Impedance protection
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