5.19
Date Code 20060320 Instruction Manual SEL-311C Relay
Trip and Target Logic
Directional Comparison Unblocking Logic
Directional Comparison Unblocking Logic
Enable the directional comparison unblocking (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 settings and logic exclusive to DCUB. 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)
The DCUB logic in Figure 5.10 takes in the loss-of-guard and permissive trip
outputs from the communications receivers (see Figure 5.12 and Figure 5.13)
and makes permissive (PTRX1/PTRX2) and unblocking block (UBB1/UBB2)
logic output decisions.
Use Existing
SEL-321 DCUB
Application Guide for
the SEL-311C
Use the existing SEL-321 DCUB application guide (AG96-19) to help set up
the SEL-311C in a DCUB scheme (see Communications-Assisted Trip
Logic-General Overview on page 5.10 for more setting comparison
information on the SEL-321/SEL-311C relays).
External Inputs
See Optoisolated Inputs on page 7.3 for more information on optoisolated
inputs.
PT1, PT2—Received Permissive Trip Signal(s)
In two-terminal line DCUB applications (setting ECOMM = DCUB1), a
permissive trip signal is received from one remote terminal. One optoisolated
input on the SEL-311C (e.g., input IN104) is driven by a communications
equipment receiver output (see Figure 5.12). Make SEL
OGIC control equation
setting PT1:
PT1 = IN104 (two-terminal line application)
In three-terminal line DCUB applications (setting ECOMM = DCUB2),
permissive trip signals are received from two remote terminals. Two
optoisolated inputs on the SEL-311C (e.g., inputs IN104 and IN106) are driven
by communications equipment receiver outputs (see Figure 5.13). Make
SEL
OGIC control equation settings PT1 and PT2 as follows:
PT1 = IN104 (three-terminal line application)
PT2 = IN106
SELOGIC control equation settings PT1 and PT2 are routed into the DCUB
logic in Figure 5.10 for “unblocking block” and “permissive trip receive”
logic decisions.
As explained in Permissive Overreaching Transfer Trip Logic on page 5.13,
the SEL
OGIC control equation settings PT1 and PT2 in Figure 5.5 are routed
in various combinations to control Relay Word bit PT, depending on enable
setting ECOMM = DCUB1 or DCUB2. Relay Word bit PT is then an input
into the POTT logic in Figure 5.6 (for echo keying).
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