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Zone lnterlocking
Zone
lnterlocking
7on"
int"tfo"kingicapability is
provided as standard on
trip
units with short time or
ground
fault
protection,
but
additional
""*p""""t.
and
wirin!
are required
to
connect
trip
units
tog"ih"t
into
a
functioning zone-interlocked
system'
Zone
selective
interlocking of series
connected circuit
break-
eI
proviOes tor
a
closer cdordination
of
short
time and
ground
fauli protection
in a
power distribution network
When
a
zone
inieirircr
type fault current is detected, the
trip
units send
a
;i";k;g
slgnal notifying the upstream
ci,rcuit
breakers
that
the
irr[
i."o"i.g
cteareo"at
a
lower
level lf a
circuit
breaker
experiencing"the
fault
receives
a blocking signal'
it
executes
if.l,I6rft
prot"ection
function based
on
the programmed
short
iinlu
oi
ground fault time delay
band
lf
it
does
not
receive
a
nfoLf.,nd
signal,
it
executes
the fault
protection
function
based
dn
th"e
minimum
delay
band
This
coordinated proce-
Ori" p."iO"s
for
a
high
level of
fault
protection
to the
bus
structure
between the zones.
If,
for
some reason,
the fault current
is
not cleared by
the
i,iooino
of
the
lowest level
circuit
breaker experiencing
the
iulii
ili"
r',igl',er
ievet
circuit
breakers' trip units continue their
pr;-b;;At#-,.ed
tripping functions
at their set
time
delavs'
Static
Trip
lll trip
units may be connected together
to
form
a
Ion"
int,jifo"k
network.
They may also
be
connected into
a
,on"
ini"rfo"k
network
witl-L
Siemens'
molded case
and/or
,rrlut"O
case circuit breakers'
trip units
The
connection
of
btr;i;irip-il'l
trlp units
into a
zone interlock network
is
with
a
fVrfiipf"x'"rnranslator
or
with Zone Interlock Expander(s) and
Zone tntertock Couplers
(see
Accessories
section)
The
1
5-pin
sub "D"
connector
on
ih"
front
of
the
trip
unit
is
used
in
"onn""t,Ctf',e
trip
unit into the
network'
The
zone interlock
"ln/
Ort; .*t""n
on
thb front
of
the
trip
unit
provides
local
configu-
Ltion
control.
Setthezone interlockswitch
tothe'Out"
position
*f,en
not
used
in
azone interlock
network
to avoid
selective
coordination
Problems.
Main
)--
Feeders
Example
oI
Zone lnterlocking Connectlon between Static
Trip
ll
I
devices
20

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