5.10
SEL-311C Relay Instruction Manual Date Code 20060320
Trip and Target Logic
Communications-Assisted Trip Logic-General Overview
Communications-Assisted
Trip Logic-General Overview
The SEL-311C includes communications-assisted tripping schemes that
provide unit-protection for transmission lines with the help of
communications. No external coordination devices are required.
Figure 5.4 Communications-Assisted Tripping Scheme
Refer to Figure 5.4 and the top half of Figure 5.1.
The six available tripping schemes are:
➤ Direct Transfer Trip (DTT)
➤ Direct Underreaching Transfer Trip (DUTT)
➤ Permissive Overreaching Transfer Trip (POTT)
➤ Permissive Underreaching Transfer Trip (PUTT)
➤ Directional Comparison Unblocking (DCUB)
➤ Directional Comparison Blocking (DCB)
Enable Setting
ECOMM
The POTT, PUTT, DCUB, and DCB tripping schemes are enabled with enable
setting ECOMM. Setting choices are:
ECOMM = N (no communications-assisted trip scheme enabled)
ECOMM = POTT (POTT or PUTT scheme)
ECOMM = DCUB1 (DCUB scheme for two-terminal line [communications
from one remote terminal])
ECOMM = DCUB2 (DCUB scheme for three-terminal line [communications
from two remote terminals])
ECOMM = DCB (DCB scheme)
These tripping schemes can all work in two-terminal or three-terminal line
applications. The DCUB scheme requires separate settings choices for these
applications (ECOMM = DCUB1 or DCUB2) because of unique DCUB logic
considerations.
Zone 3 (1)
Zone 1 (1)
Zone 2 (1)
Zone 1 (2)
Zone 3 (2)
Zone 2 (2)
SEL-311CSEL-311C
Bus 1
Bus 2
Comm.
Equip
Comm.
Equip
TX TX
RX
RX
Transmission Line
52
1
52
2
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