Sel SEL-421 - Communications-Assisted Tripping Logic; ECOMM Setting; Required Zone Directional Settings

R.1.87
Date Code 20111215 Reference Manual SEL-421 Relay
Protection Functions
Communications-Assisted Tripping Logic
Communications-Assisted Tripping Logic
Communications-assisted tripping schemes provide unit protection for
transmission lines without any need for external coordination devices. The
relay includes the following five schemes.
➤ POTT—Permissive-Overreaching Transfer Trip
➤ POTT2—Two-Channel Permissive Overreaching Transfer Trip
➤ POTT3—Phase-Segregated Permissive Overreaching
Transfer Trip
➤ DCUB—Directional Comparison Unblocking
➤ DCB—Directional Comparison Blocking
All of these schemes work in both two-terminal and three-terminal line
applications. For the DCUB scheme, you have separate settings choices for
these applications (ECOMM equals DCUB1 or DCUB2) because of unique
DCUB logic considerations.
You must set Zone 3 reverse-looking (DIR3 equals R) for all three schemes.
Figure 1.60 Required Zone Directional Settings
Table 1.63 ECOMM Setting
Setting Description Range
Default
(5 A)
ECOMM Communications-Assisted Tripping N, DCB, POTT,
POTT2, POTT3,
DCUB1, DCUB2
POTT
SEL-421 Relay
BK1
Transmission Line
Bus S
BK2
SEL-421 Relay
Comm.
Equip
Comm.
Equip
TX
RX
TX
RX
Bus R
Zone 3 (R)
Zone 1 (R)
Zone 2 (R)
Zone 3 (S)
Zone 1 (S)
Zone 2 (S)