CHAPTER 5: SETTINGS
GROUPED ELEMENTS
L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
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The line pickup feature uses a combination of undercurrent and undervoltage to identify a line that has been de-energized
(line end open). Alternately assign a FlexLogic operand to the
TERMINAL OPEN
setting that specifies the terminal status.
Three instantaneous overcurrent elements are used to identify a previously de-energized line that has been closed onto a
fault. Faults other than close-in faults can be identified satisfactorily with the distance elements.
Co-ordination features are included to ensure satisfactory operation when high-speed automatic reclosure (AR) is
employed. The
AR CO-ORD DELAY
setting allows the overcurrent setting to be below the expected load current seen after
reclose. Co-ordination is achieved by all of the
LINE PICKP UV
elements resetting and blocking the trip path before the
AR
CO-ORD DELAY
times out. The
AR CO-ORD BYPASS
setting is normally enabled. It is disabled if high speed autoreclosure is
implemented.
The line pickup protection incorporates zone 1 extension capability. When the line is being re-energized from the local
terminal, pickup of an overreaching zone 2 or excessive phase current within eight power cycles after the autorecloser
issues a close command results in the
LINE PICKUP RCL TRIP
FlexLogic operand. For security, the overcurrent trip is
supervised by an undervoltage condition, which in turn is controlled by the
VT FUSE FAIL OP
operand with a 10 ms
coordination timer. If a trip from distance is not required, then it can be disabled with the
LINE PICKUP DISTANCE TRIP
setting.
Configure the
LINE PICKUP RCL TRIP
operand to perform a trip action if the intent is zone 1 extension.
The zone 1 extension philosophy used here normally operates from an under-reaching zone, and it uses an overreaching
distance zone when reclosing the line with the other line end open. The
AR ACCELERATE
setting is provided to achieve zone
1 extension functionality if external autoreclosure is employed. Another zone 1 extension approach is to apply
permanently an overreaching zone, and reduce the reach when reclosing. This philosophy can be programmed via the
autoreclose scheme.
LINE PICKUP FUNCTION
— This setting enables and disables the line pickup feature.
LINE PICKUP SIGNAL SOURCE
— Selects the signal source for line pickup protection.
PHASE IOC LINE PICKUP
— Specifies the level of line current required to declare a line pickup operation when the line is re-
energized.
LINE END OPEN PICKUP DELAY
— Specifies the time during which the line is de-energized before the line pickup logic is
armed.
LINE END OPEN RESET DELAY
— Specifies the time during which the line pickup logic remains armed once the line has been
re-energized.
AR CO-ORD BYPASS
— The coordination timer allows the overcurrent detector to be set below the expected load current
seen after reclose. When this setting is enabled (the default value), the coordination timer is bypassed. Disable this setting
(removing the bypass and inserting the timer) if high speed autoreclosure is employed.
AR CO-ORD PICKUP DELAY
— If the setting of the overcurrent detector is less than the load current, then it picks up during a
normal re-energization of the line. This setting delays the assertion of the
LINE PICKUP OP
operand, allowing the recovery of
the line voltage to block the scheme.
AR CO-ORD RESET DELAY
— This setting extends the assertion of the line pickup output when autoreclose coordination is not
bypassed.
TERMINAL OPEN
— This setting allows the line pickup element to be armed from a status signal (such as breaker position)
rather than from current and voltage. The FlexLogic operand assigned to this setting indicates that the terminal is opened.
It can be derived by combining the status of several devices in a FlexLogic equation.
AR ACCELERATE
— This setting provides zone 1 extension functionality if external autoreclosure is employed.
LINE PICKUP BLOCK
— Assertion of the FlexLogic operand assigned to this setting blocks operation of the line pickup
element.
LINE PICKUP EVENTS
— This setting enables and disables the logging of line pickup events in the sequence of events
recorder.
