Date Code 20010731
Close Logic
4-15
SEL-352-1, -2 Instruction Manual
first, B-phase second, and C-phase third. If you want a different order, add a 1-cycle offset to the
phase you need to delay.
R
ETRIPPING
Application Description
The SEL-352 Relay default logic provides two retripping schemes. Scheme 1 is an
instantaneous retrip and Scheme 2 is a time-delayed, current-supervised retrip. Use the
SET
command to modify these schemes for your application.
Retripping is a cost-effective, secondary attempt to open a circuit breaker prior to breaker failure
protection resulting in clearing of the entire bus and remote breakers. Many conditions may
cause a breaker to fail to respond to a trip signal. Faulty breaker mechanical components, open
trip coil, shorted trip coil, failed auxiliary contact, low battery dc, and open trip coil circuit are
all possible conditions that may cause a breaker not to open. Some of these conditions will
require that all adjacent breakers be opened, but some of the conditions may only require another
trip signal. Some breakers have multiple trip coils that are energized with a retrip signal. A
retrip signal provides partial redundancy for the trip coil circuitry. A separate tripping dc and
trip coil provide full tripping circuit redundancy.
Retripping also provides security during inadvertent breaker failure initiation. If the trip input is
inadvertently asserted, the retrip logic will attempt to trip the breaker prior to clearing the bus.
Operating Characteristic
Scheme 1 (Instantaneous Retrip)
Relay Word elements RTA, RTB, and RTC simply follow the input assignments TRIPA, TRIPB,
and TRIPC, respectively.
Scheme 2 (Delayed Retrip)
Figure 4.11: Circuit Breaker Retrip Logic (Scheme 2), A-Phase
Содержание SEL-352-1
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