Schweitzer Engineering Laboratories SEL-351 - Date Code 20001006 Trip and Target Logic; Directional Comparison Unblocking (DCUB) Logic

Date Code 20001006 Trip and Target Logic 5-19
SEL-351 Instruction Manual
Figure 5.8: SEL-351 Relay Connections to Communications Equipment for a Two-Terminal
Line POTT Scheme (Model 0351xT Example)
Figure 5.9: SEL-351 Relay Connections to Communications Equipment for a
Three-Terminal Line POTT Scheme (Model 0351xT Example)
DIRECTIONAL COMPARISON UNBLOCKING (DCUB) LOGIC
Enable the DCUB logic by setting ECOMM = DCUB1 or ECOMM = DCUB2. The DCUB logic
in Figure 5.10 is an extension of the POTT logic in Figure 5.6. Thus, the relay requires all the
POTT settings and logic, plus exclusive DCUB settings and logic. The difference between setting
choices DCUB1 and DCUB2 is:
DCUB1 directional comparison unblocking scheme for two-terminal line (communications
from one remote terminal)
DCUB2 directional comparison unblocking scheme for three-terminal line
(communications from two remote terminals)
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