Pilot Schemes - GE L60 Instructions Manual

CONTROL ELEMENTS

5.7.10 Pilot schemes

5.7.10.1 Permissive overreaching transfer trip (POTT)
SETTINGS  CONTROL ELEMENTS  PILOT SCHEMES  POTT SCHEME
 POTT SCHEME

5
This scheme is intended for two-terminal line applications only. It uses an over-reaching zone 2 distance element to
essentially compare the direction to a fault at both the ends of the line. Ground directional overcurrent functions available
in the relay can be used in conjunction with the zone 2 distance element to key the scheme and initiate its operation. This
provides increased coverage for high resistance faults.
For proper scheme operation, enable and configure the zone 2 phase and ground distance elements per the rules of
distance relaying. Enable and configure the line pickup element to detect line-end-open/weak-infeed conditions. If used by
this scheme, enable and configure the selected ground directional overcurrent functions accordingly.
POTT PERMISSIVE ECHO
permissive signal is echoed back upon receiving a reliable
condition is identified by the line pickup logic. The permissive echo is programmed as a one-shot logic. The echo is sent
only once and then the echo logic locks out for a settable period of time (
pulse does not depend on the duration or shape of the received
POTT RX PICKUP DELAY
longest spurious
TX
time of the scheme.
TRANS BLOCK PICKUP DELAY
coping with the exposure of a ground directional overcurrent function (if used) to current reversal conditions. The transient
blocking mechanism applies to the ground overcurrent path only as the reach settings for the zone 2 distance functions is
not expected to be long for two-terminal applications, and the security of the distance functions is not endangered by the
5-344
POTT SCHEME

FUNCTION: Disabled
POTT PERMISSIVE

ECHO: Disabled
POTT RX PICKUP

DELAY: 0.000 s
TRANS BLOCK PICKUP

DELAY: 0.020 s
TRANS BLOCK RESET

DELAY: 0.090 s
ECHO DURATION:

0.100 s
ECHO LOCKOUT:

0.250 s
LINE END OPEN PICKUP

DELAY: 0.050 s
POTT SEAL-IN

DELAY: 0.400 s
GND DIR O/C FWD:

Off
POTT RX:

Off
POTT SCHEME TARGET:

Self-reset
POTT SCHEME EVENT:

Disabled
— When "Enabled," this setting results in a permissive echo signal being sent to the remote end. The
— This setting enables the relay to cope with spurious receive signals. Set the delay longer than the
signal that can occur simultaneously with the zone 2 pickup. The selected delay increases the response
— This setting defines a transient blocking mechanism embedded in the POTT scheme for
Range: Disabled, Enabled
Range: Disabled, Enabled
Range: 0.000 to 65.535 s in steps of 0.001
Range: 0.000 to 65.535 s in steps of 0.001
Range: 0.000 to 65.535 s in steps of 0.001
Range: 0.000 to 65.535 s in steps of 0.001
Range: 0.000 to 65.535 s in steps of 0.001
Range: 0.000 to 65.535 s in steps of 0.001
Range: 0.000 to 65.535 s in steps of 0.001
Range: FlexLogic operand
Range: FlexLogic operand
Range: Self-reset, Latched, Disabled
Range: Disabled, Enabled
signal from the remote end while the line-end-open
POTT RX
ECHO LOCKOUT
signal but is settable as
POTT RX
L60 LINE PHASE COMPARISON SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS
setting). The duration of the echo
.
ECHO DURATION