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5.7 CONTROL ELEMENTS
•
LINE END OPEN PICKUP DELAY: This setting defines the pickup value for validation of the line end open conditions
as detected by the Line Pickup logic through the
condition is a requirement for the POTT scheme to return a received echo signal (if the echo feature is enabled). This
value should take into account the principle of operation and settings of the Line Pickup element.
•
POTT SEAL-IN DELAY: The output FlexLogic operand (
seal-in time delay is applied to this operand for coping with noisy communication channels. The
defines a minimum guaranteed duration of the
scheme, the trip operands
•
GND DIR O/C FWD: This setting defines the FlexLogic operand (if any) of a protection element that is used in addition
to the Zone 2 for 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 protec-
tion element used as
ing the user to combine 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. Both of these elements have separate forward (
output operands. The forward indication should be used (
security and to overcome spurious directional element operation during transients, adding at least 0.5 cycles of pickup
delay to the forward directional element is recommended.
•
POTT NO OF COMM BITS: This setting specifies the number of bits of the communications channel available for the
scheme. The transmit codes and trip tables of the POTT scheme are the same as those for the permissive under-
reaching transfer trip scheme. Please refer to the description of the PUTT scheme for more information.
•
POTT RX1 through POTT RX4: These settings allow the user to select the FlexLogic operands that represent the
receive signals for the scheme. Typically input contacts interfacing with a signaling system are used. In single-bit appli-
cations,
5
POTT RX1
,
POTT RX1
POTT RX2
5-304
,
,
and
POTT TRIP A
B
C
. Even though any FlexLogic operand could be used as
GND DIR O/C FWD
must be used. In two-bit applications,
,
, and
must be used.
POTT RX3
POTT RX4
L90 Line Current Differential System
FlexLogic operand. The validated line end open
LINE PICKUP LEO PKP
) is produced according to the POTT scheme logic. A
POTT OP
pulse. As this operand activates the trip table of the POTT
POTT OP
are sealed-in for the same period of time.
3P
NEG SEQ DIR OC1 FWD
and
POTT RX1
POTT RX2
5 SETTINGS
POTT SEAL-IN DELAY
GND DIR O/C FWD
) and reverse (
FWD
or
). For greater
NEUTRAL DIR OC1 FWD
must be used. In four-bit applications,
GE Multilin
allow-
)
REV
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