Date Code 20010731
Close Logic
4-1
SEL-352-1, -2 Instruction Manual
SECTION 4: CLOSE LOGIC
B
REAKER
C
ONTROL
O
VERVIEW
Manual and automated breaker control through the SEL-352 Relay has many advantages:
consolidated wiring, sequential event records, no auxiliary relay required, and flexible logic,
which all reduce total installation and operation costs.
All SEL-352 Relay output contacts and optoisolated inputs are programmable, except for the
ALARM output contact. Set the SEL-352 Relay inputs and outputs to control the connected
equipment appropriately.
C
ONTROLLED
C
LOSING
Application Description
Two controlled closing schemes are provided for reducing system transients. Each scheme
supports automatic and manual closing.
Use Scheme 1 for staggered closing of independent breakers to reduce transients when you do
not have PTs on both sides of your breaker or do not know your breaker operation time. Set the
staggered close times to a time greater than the transient time but less than the time the system
can tolerate a single-pole condition.
Use Scheme 2 for synchronized and point-on-wave closing when PTs are available on both sides
of your breaker. Synchronized closing is used when both sides of a breaker are live. The logic
determines when the two sides are in phase and closes the breaker at that time to minimize
transients. Point-on-wave closing is used when one side of the breaker is live and the other is
dead. The logic accommodates negative, zero, and positive trapped charge due to capacitor
banks, etc., to minimize the voltage across the breaker at closing.
Operating Characteristic
Scheme 1 (Staggered Close)
Scheme 1 of the controlled closing logic is intended for breakers that have separate close coil
circuits for each pole. When closing all breaker poles at the same time, differences in where
poles close on the voltage waveform can cause transients that can cause system damage or
degradation. This scheme can limit the amount and severity of transients by staggering the close
operation of each individual pole.
Set the pickup time for each phase timer, selecting the delay for each individual phase.
Figure 4.1 illustrates this logic for A-phase. B-phase logic and C-phase logic are similar.
Содержание SEL-352-1
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