GE L90 Instruction Manual page 552

CONTROL ELEMENTS
Set this delay long enough to cope with transient conditions including not only current reversals but also spurious negative
and zero-sequence currents occurring during breaker operations (in the case when neutral directional overcurrent or
negative-sequence directional overcurrent functions are used). Consider the breaker failure time of the surrounding
protection systems within the reach of the ground directional function used by the hybrid POTT scheme, 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 is not dependent
ECHO DURATION
on the duration and shape of received RX signals. This setting enables the relay to avoid a permanent lock-up of the
transmit/receive loop.
— This setting defines the lockout period for the echo logic after sending the echo pulse. This enables the
ECHO LOCKOUT
relay to avoid oscillations of the echo pulses during an autoreclosure dead-time after clearing an internal fault.
HYB POTT SEAL-IN DELAY
logic. The
HYB POTT SEAL-IN DELAY
the trip table of the hybrid POTT scheme, the trip operands
time.
— This setting defines the FlexLogic operand (if any) of a protection element that is used in addition to
GND DIR O/C FWD
zone 2 for identifying faults on the protected line, and thus, for keying the communication channel and initiating operation
of the scheme (both through the transient blocking logic). Good directional integrity is the key requirement for an over-
reaching forward-looking protection element used as
Even though any FlexLogic operand could be used as
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 or neutral directional overcurrent elements. Both these
elements have separate forward (FWD) and reverse (REV) output operands. The forward indication should be used (
or
DIR OC1 FWD NEUTRAL DIR OC1 FWD
5
Coordinate the selected protection element (or elements in combination) with the selection of
forward external faults seen by an element used as
used as
GND DIR O/C REV
spurious directional element operation during transients, adding at least 0.5 cycles of pickup delay to the forward
directional element is recommended.
— This setting defines the FlexLogic operand (if any) of a protection element used in addition to zone 4 for
GND DIR O/C REV
identifying reverse faults, and thus, for stopping the transmit signal and initiating the transient blocking timer. Good
directional integrity is the key requirement for a reverse-looking protection element used as
Even though any FlexLogic operand can be used as
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 or neutral directional overcurrent element. Both these
elements have separate forward (FWD) and reverse (REV) output operands. Use the reverse indication (
or
NEUTRAL DIR OC1 REV
Coordinate the selected protection element (or elements in combination) with the selection of
forward external faults seen by an element used as
used as
GND DIR O/C REV
spurious directional element operation during transients, adding a pickup delay greater than the pilot channel delay to the
reverse directional element is recommended.
HYB POTT NO OF COMM BITS
scheme. The transmit codes and trip table of the hybrid POTT scheme are the same as those for the permissive under-
reaching transfer trip scheme. See the description of the PUTT scheme for information.
through
HYB POTT RX1
receive signals for the scheme. Typically, input contacts interfacing with a signaling system are used. In single-bit
applications,
HYB POTT RX1
applications,
HYB POTT RX1
5-366
— The output FlexLogic operand
defines a minimum guaranteed duration of the
).
at the other end picks up and provides a blocking signal. For greater security and to overcome
).
at the other end picks up and provides a blocking signal. For greater security and to overcome
— This setting specifies the number of bits of the communications channel available for the
— These settings allow the user to select the FlexLogic operands that represent the
HYB POTT RX4
must be used. In two-bit applications,
, ,
HYB POTT RX2 HYB POTT RX3
(HYB POTT OP) is produced according to the hybrid POTT scheme
A, B, C, and
HYB POTT TRIP
.
GND DIR O/C FWD
enabling the user to combine responses of various
GND DIR O/C FWD
at one end of the line, the reverse-looking element
GND DIR O/C FWD
enabling the user to combine responses of various
GND DIR O/C REV
at one end of the line, the reverse-looking element
GND DIR O/C FWD
and
HYB POTT RX1
, and must be used.
HYB POTT RX4
L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS
pulse. As this operand runs
HYB POTT OP
are sealed-in for the same period of
3P
. For all the
GND DIR O/C REV
.
GND DIR O/C REV
NEG SEQ DIR OC1 REV
. For all the
GND DIR O/C FWD
must be used. In four-bit
HYB POTT RX2
NEG SEQ