
7
Date Code 20200326
SEL Application Guide 2020-04
Table 5
SEL-421-5 POTT Settings
Setting
Setting Description
Settings Value Description
ECOMM
Enable Communication
Scheme
POTT
Enables the POTT logic in the SEL-421-5.
Z3RBD
Zone 3 Reverse Block Time
Delay
5 (default)
Prevents a POTT scheme misoperation during a current
reversal.
EBLKD
Echo Block Time Delay
10 (default)
Prevents the echoing of a received PT for a settable delay
after the dropout of the local permissive elements.
ETDPU
Echo Time Delay Pickup
2 (default)
Sets a minimum time requirement for the received PT
before echo begins.
EDURD
Echo Duration Time Delay
4 (default)
Limits the echo duration to prevent channel lockup.
EWFC
Weak-Infeed Enable
N (default)
Allows echo keying in the event of a weak terminal or an
open breaker.
Table 6
SEL-311C-1 POTT Settings
Setting
Setting Description
Settings Value Description
ECOMM
Enable Communication
Scheme
POTT
Enables the POTT logic in the SEL-311C-1.
Z3RBD
Zone 3 Reverse Block Time
Delay
5 (default)
Prevents a POTT scheme misoperation during a current
reversal.
EBLKD
Echo Block Time Delay
10 (default)
Prevents the echoing of a received PT for a settable delay
after the dropout of the local permissive elements.
ETDPU
Echo Time Delay Pickup
2 (default)
Sets a minimum time requirement for the received PT
before echo begins.
EDURD
Echo Duration Time Delay
4 (default)
Limits the echo duration to prevent channel lockup.
EWFC
Weak-Infeed Enable
N (default)
Allows echo keying in the event of a weak terminal or an
open breaker.
Table 7
SEL-321-1 POTT Settings
Setting
Setting Description
Settings Value Description
EPOTT
Enable Permissive Overreach-
ing Transfer Trip
Y
Enables the POTT logic in the SEL-321-1.
Z3RBD
Zone 3 Reverse Block Time
Delay
5 (default)
Prevents a POTT scheme misoperation during a current
reversal.
EBLKD
Echo Block Time Delay
10 (default)
Prevents the echoing of a received PT for a settable delay
after the dropout of the local permissive elements.
ETDPU
Echo Time Delay Pickup
2 (default)
Sets a minimum time requirement for the received PT
before echo begins.
EDURD
Echo Duration Time Delay
4 (default)
Limits the echo duration to prevent channel lockup.
EWFC
Weak-Infeed Enable
N (default)
Allows echo keying in the event of a weak terminal or an
open breaker (requires EVOLT = Y).