
Date Code 20020215
Trip and Target Logic
5-13
SEL-351R Instruction Manual
The SEL-321 Relay handles trip unlatching with setting TULO. The SEL-351R handles trip
unlatching with SEL
OGIC
control equation setting ULTR.
The SEL-321 Relay has single-pole trip logic. The SEL-351R does not have single-pole trip
logic.
P
ERMISSIVE
O
VERREACHING
T
RANSFER
T
RIP
(POTT) L
OGIC
Enable the POTT logic by setting ECOMM = POTT. The POTT logic in Figure 5.6 is also
enabled for directional comparison unblocking schemes (ECOMM = DCUB1 or
ECOMM = DCUB2). The POTT logic performs the following tasks:
•
Keys communication equipment to send permissive trip when any element included in the
SEL
OGIC
control equation communications-assisted trip equation TRCOMM asserts and
the current reversal logic is not asserted.
•
Prevents keying and tripping by the POTT logic following a current reversal.
•
Echoes the received permissive signal to the remote terminal.
•
Prevents channel lockup during echo and test.
•
Provides a secure means of tripping for weak- and/or zero-infeed line terminals.
Use Existing SEL-321 Relay POTT Application Guide for the SEL-351R Recloser Control
Use the existing SEL-321 Relay POTT application guide (AG95-29) to help set up the
SEL-351R in a POTT scheme (see preceding subsection
for more setting comparison information on the SEL-321/SEL-351R).
External Inputs
See
Optoisolated Inputs
in
Section 7: Inputs, Outputs, Timers, and Other Control Logic
for
more information on optoisolated inputs.
PT1 — Received Permissive Trip Signal(s)
In two-terminal line POTT applications, a permissive trip signal is received from one remote
terminal. One optoisolated input on the SEL-351R (e.g., input IN104) is driven by a
communications equipment receiver output (see Figure 5.8). Make SEL
OGIC
control equation
setting PT1:
PT1 = IN104
(two-terminal line application)
In three-terminal line POTT applications, permissive trip signals are received from two remote
terminals. Two optoisolated inputs on the SEL-351R (e.g., input IN104 and IN106) are driven
by communications equipment receiver outputs (see Figure 5.9). Make SEL
OGIC
control
equation setting PT1 as follows:
PT1 = IN104 * IN106
(three-terminal line application)
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