GE D60 Instruction Manual page 395

5 SETTINGS
• 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
open 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 (
A 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 addi-
tion to the Zone 2 for identifying faults on the protected line, and thus, for keying the communication channel and initi-
ating operation of the scheme. Good directional integrity is the key requirement for an over-reaching forward-looking
protection element used as
allowing the user to combine responses of various protection elements, or to apply extra conditions through Flex-
FWD
Logic™ 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 (
reverse ( ) output operands. The forward indication should be used (
REV
). For greater security and to overcome spurious directional element operation during transients, adding at least
FWD
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, must be used. In two-bit applications,
POTT RX1
, ,
POTT RX1 POTT RX2 POTT RX3
GE Multilin
LINE PICKUP LEO PKP
POTT OP
, , and are sealed-in for the same period of time.
POTT TRIP A B C 3P
. Even though any FlexLogic™ operand could be used as
GND DIR O/C FWD
, and must be used.
POTT RX4
D60 Line Distance Protection System
FlexLogic™ operand. The validated line end
) is produced according to the POTT scheme logic.
POTT OP
pulse. As this operand activates the trip table of the POTT
NEG SEQ DIR OC1 FWD
and must be used. In four-bit applications,
POTT RX1 POTT RX2
5.7 CONTROL ELEMENTS
POTT SEAL-IN DELAY
GND DIR O/C
) and
FWD
or
NEUTRAL DIR OC1
5-261
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