GE L60 Instruction Manual page 491

CHAPTER 5: SETTINGS
current reversal conditions. Upon receiving the
passed and aligned with the
GND DIR O/C FWD
After that the ground directional overcurrent path is virtually disabled for a period of time specified as
.
DELAY
Set the
TRANS BLOCK PICKUP DELAY
operate, but not longer than the fastest possible operation time of the protection system that can create current reversal
conditions within the reach of the selected ground directional overcurrent function. For this setting, also take into account
the . The
POTT RX PICKUP DELAY
original signal is delayed by the
RX
the original signal, and eventually, locked-out for
POTT TX
— This setting defines a transient blocking mechanism embedded in the POTT scheme for
TRANS BLOCK RESET DELAY
coping with the exposure of a ground directional overcurrent function (if used) to current reversal conditions (see also the
). Set this delay long enough to cope with transient conditions including not only current
TRANS BLOCK PICKUP DELAY
reversals but also spurious negative and zero-sequence currents occurring during breaker operations. The breaker failure
time of the surrounding protection systems within the reach of the ground directional function used by the POTT scheme
can be considered to make sure that the ground directional function is not jeopardized during delayed breaker operations.
— This setting defines the guaranteed and exact duration of the echo pulse. The duration does not depend
ECHO DURATION
on the duration and shape of the received
transmit/receive loop.
— This setting defines the lockout period for the echo logic after sending the echo pulse.
ECHO LOCKOUT
— This setting defines the pickup setting for validation of the line end open conditions as
LINE END OPEN PICKUP DELAY
detected by the Line Pickup logic through the
is a requirement for the POTT scheme to return a received echo signal (if the echo feature is enabled). Also for this setting,
take into account the principle of operation and settings of the line pickup element.
— The output FlexLogic operand
POTT SEAL-IN DELAY
time delay is applied to this operand for coping with noisy communication channels. This setting specifies a minimum
guaranteed duration of the
POTT OP
— This setting selects the FlexLogic operand (if any) of a protection element used in addition to zone 2 for
GND DIR O/C FWD
identifying faults on the protected line, and thus, for keying the communication channel and initiating operation of the
scheme. Good directional integrity is the key requirement for an over-reaching forward-looking protection element used as
. Even though any FlexLogic operand can be used as
GND DIR O/C FWD
responses of various protection elements, or to apply extra conditions through FlexLogic equations, this extra signal is
primarily meant to be the output operand from either the negative-sequence directional overcurrent or neutral directional
overcurrent elements. Both of these elements have separate forward and reverse output operands. The forward indication
should be used (
NEG SEQ DIR OC1 FWD
element operation during transients, adding at least 0.5 cycles of pickup delay to the forward directional element is
recommended.
— This setting enables the user to select the FlexLogic operand that represents the receive signal (RX) for the
POTT RX
scheme. Typically an input contact interfacing with a signaling system is used. Other choices include remote inputs and
FlexLogic equations. The POTT transmit signal (TX) should be appropriately interfaced with the signaling system by
assigning the output FlexLogic operand
The output operand from the scheme
in particular, in order to make the scheme fully operational. Typically, the output operand should be programmed to initiate
a trip, breaker fail, and autoreclose, and drive a user-programmable LED as per user application.
L60 LINE PHASE COMPARISON SYSTEM – INSTRUCTION MANUAL
signal, the transient blocking mechanism allows the
POTT RX
indication only for a period of time defined as
long enough to give the selected ground directional overcurrent function time to
signal is shaped for aligning with the ground directional indication as follows: the
POTT RX
, then terminated at
POTT RX PICKUP DELAY
TRANS BLOCK RESET DELAY
signal. This setting enables the relay to avoid a permanent lock-up of the
POTT RX
LINE PICKUP LEO PKP
(POTT OP) is produced according to the POTT scheme logic. A seal-in
pulse.
or
NEUTRAL DIR OC1 FWD
(POTT TX) to an output contact. The remote output mechanism is another choice.
(POTT OP) must be configured to interface with other relay functions, output contacts
TRANS BLOCK PICKUP DELAY
.
FlexLogic operand. The validated line end open condition
allowing the user to combine
GND DIR O/C FWD
). For greater security and to overcome spurious directional
CONTROL ELEMENTS
signal to be
RX
.
TRANS BLOCK PICKUP DELAY
TRANS BLOCK RESET
after the pickup of
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