Weakfeed System Application; Reclose Block On Breaker Failure Squelch; Programmable Contact Outputs - ABB REL 301 Instruction Leaflet

I.L. 40-386.4
permission is received from the weak terminal. The pilot trip relay(s) at the weak terminal
cannot operate since there is insufficient fault energy, and does not perform the normal key-
ing function. With one weakfeed condition, when the weak end receives a permissive (or
unblocking) signal, the output from the receiver operates the echo key logic via AND 65A,
providing both pilot relay (from OR 40) and reverse logic (from REVERSE BLOCK LOGIC)
have not operated and if system disturbance is detected (∆V or∆I). Output of AND 65A will
key the weak terminal transmitter to the permissive (or unblocking) frequency via OR 18,
AND 35. On weak end reverse external fault, the strong source terminal(s) send the per-
missive (or unblocking) frequency signal to the weak end, and the strong source terminal(s)
pilot trip relay(s) wait to receive the echo trip permission from the weak end. However, at
the weak end, the echo key logic AND 65A will not operate, because of the REVERSE
BLOCK LOGIC operation. Both the strong/weak terminals will not trip on this external fault.
2) Weak end trip on internal fault (Figure 2-30)
The output of AND 65A (echo keying) together with no output from OR 40 (pilot trip relays),
no output from the REVERSE BLOCK LOGIC and with output from OR 44 (low voltage con-
dition) will satisfy AND 66. Weakfeed trip (a high speed trip) will occur after 50 ms via OR
2 (Figure 2-5). The time delay is for coordination because the voltage trip units are non-di-
rectional.
2.5.6.1

Weakfeed System Application

For weakfeed applications, an inherent part of the logic requires reverse fault detection; Zone-3
Ø/Zone-3 G and RDOG, which are a part of the REVERSE BLOCK LOGIC, supply this require-
ment.
2.5.7

Reclose Block on Breaker Failure Squelch

For a pilot system, the BFI signal can be used to stop (for a blocking system) or start (for per-
missive schemes) the carrier channel and allow the remote terminal to trip should the local
breaker fail to trip. The problem is how to inhibit the remote terminal from reclosing.
REL301/302 solves this problem by the with the RemBF RB squelch logic in the reclosing initi-
ation logic. The logic, as shown in Figure 2-18, includes AND 61A and a 132/0 millisecond tim-
er.
If the "RemBF RB" is set to "Yes" the logic will initiate reclose block (RB) 132 ms after the fault
is detected by ∆V or ∆I, assuming the pilot is enabled and the TRSL signal is received on any
pilot trip operation.
2. 6

PROGRAMMABLE CONTACT OUTPUTS

Most of the functions described in this section can be directed (single or combined) to the pro-
grammable contact outputs. Refer to Section 4.10 for further details.
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