5.13
Date Code 20060320 Instruction Manual SEL-311C Relay
Trip and Target Logic
Permissive Overreaching Transfer Trip Logic
Permissive Overreaching Transfer Trip Logic
Enable the permissive overreaching transfer trip (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 communications 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-311C
Use the existing SEL-321 POTT application guide (AG95-29) to help set up
the SEL-311C in a POTT 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—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-311C (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-311C (e.g.,
inputs 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)
SEL
OGIC control equation setting PT1 in Figure 5.5 is routed to control Relay
Word bit PT if enable setting ECOMM = POTT. Relay Word bit PT is then an
input into the POTT logic in Figure 5.6 (for echo keying).
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