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MaGnuM PRoDuct GuiDe
CA013002EN—April 2017 www.eaton.com
63
Applications and other miscellaneous engineering data
Applications for Magnum circuit breakers
•
Zone selective
interlocking
Zone interlocking is a
communication scheme
used with circuit breakers
and protective relays
to improve the level of
protection in a power
distribution system .
This is achieved through
transmission of a restraint
signal between the
downstream and upstream
devices in the system .
The word “zone” is used
to refer to the part of an
installation between two
circuit breakers in series .
The zones are classified by
their location downstream
of the main circuit protective
device, which is generally
defined as zone 1 .
Zone selective interlocking
(or zone interlocking) is
available with the Digitrip
family of trip units on the
Short Delay and Ground
Fault protection functions .
The Zone Selective
Interlocking function on the
Digitrip family of breakers
has combined the logic
interlocking of short delay
and ground fault . It provides
the fastest possible tripping
for faults within the zone of
protection of the breaker,
and yet also allows selective
positive coordination among
all breakers in the system
(mains, ties, feeders, and
downstream breakers) to
limit a power outage to only
the affected parts of the
system . For IEC Digitrip trip
units, the zone selective
interlocking feature between
breakers is defeated .
When zone interlocking is
employed, a fault within
the zone of protection of
the breaker will cause the
Digitrip trip unit to:
•
Trip the affected breaker
immediately and, at the
same time . . .
•
. . .Send a signal to
upstream Digitrip
units to restrain them
from reducing their
programmed trip times .
The restraining signal
causes the upstream
breakers to follow their set
coordination times, so that
the service is only minimally
disrupted while the fault is
cleared in the shortest time
possible .
•
Low voltage high
resistance ground fault
sensing
Where continuity of service
is a high priority, high-
resistance grounding can
add the safety of a grounded
system while minimizing the
risk of service interruptions
due to grounds . The concept
is a simple one: provide
a path for ground current
via a resistance that limits
the current magnitude,
and monitor to determine
when an abnormal condition
exists . This provides for
maximum continuity of
service, because no tripping
occurs for the resistance
limited ground fault .
The ground current path
is provided at the point
where the service begins,
by placing resistance in the
connection from system
neutral to ground .
•
Phasing on double-wide
application
Magnum circuit breakers
manufactured in the
double-wide frame have
two available phasing
configurations which must
be confirmed when the
breaker is ordered .
The phasing convention is
determined facing the front
of the breaker from left to
right . For 4-pole applications,
the neutral is located on the
left and is rated 100% of the
breaker continuous current
rating .
The following phasing
configurations are available:
•
3-Pole AABBCC
•
4-Pole NNAABBCC
•
3-Pole ABCABC
•
4-Pole NNABCABC
•
4-Pole NABCNABC
The type of phasing
selected depends on how
the circuit breaker will be
applied in the enclosure and
the type of Eaton power
distribution enclosure that it
will be applied in .
AABBCC or NNAABBCC
phasing
AABBCC phasing is the
convention commonly used
in Eaton switchboards
using Magnum breakers,
including IEC switchboards .
The AABBCC convention
is recommended for most
OEMs manufacturing their
own power distribution
enclosures . It is ideal for
applications where the
breaker is mounted single
high (one breaker in a
structure) .
ABCABC or NABCNABC
phasing
ABCABC phasing is the
convention commonly used
in Eaton Magnum UL1558
switchgear . Double-wide
breakers with this type of
phasing are designed to
accommodate 2 sets of
vertical risers in the same
structure . This provides for
significant space savings
because two or more
standard frame feeder
breakers can be mounted
above or below the
double-wide breaker in
the same structure .
The ABCABC convention
is more difficult for OEMs
who manufacture their
own power distribution
enclosures to apply .
Switchgear bus design and
testing as well as placement
and balance of the feeder
breaker loads are very
important to assure that
phase currents divide evenly
through the double-wide
breaker . ABCABC phasing is
available, but not common in
IEC switchgear applications .
Contact Eaton for more
information .
Magnum double-wide
frame breaker with
AABBCC phasing
(front and rear views)
