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Principles
of OPeration
v
User
Control
iil'";lt;i*;nts
and switches
on the
trip
unit's,face and
the
progiur;ing
via the
c-ommunications
ports
allow
the
user
control of the
trip
,n't
gy
these
means
the user selects
the
irr"ii"ur
valuei
and sofiware routines' stored
in
the memory
"n"ritr,
it-,urrre
to be
used
by the
microprocesso-rs
in
perform-
i."
ir-l.ii functions.
The
selection and programming
process
i
;.tI;r;"".1g"'"0
i"
L"
straignt
forward and
user
f
riendlv
to
inl*J"gt";
thi
tt","
lnt"in,l
op"eration
of the
trip
unit
is
totally
transparent to
the
user'
Current Sensors
6rii".i"*ioita
for
fault protection and metering
are
derived
from special purpose
"*["tt
sensors mounted
in
the circuit
breaker. These current sensors
are
toroidal current transform-
"i.-n.
prl.i"e
Oeuices
if'ey
provide
high reliability with mini-
,rr'.i6.ri
"iror.
The rated primarv
"'ll:!l^:f
the
sensors
establish the maxrmum
"ontin'o"
cLrrent rating
of
the
circuit
breaker, The rated
.""6nOuty
current for the sensors is
0
5
2mnores at rated
o'imutv
C'it"nt
Atl
the sensors used
with
Silil
fnoil, tio ,iiLt
,,.,j""tapsulated
in
polvme'ic
material
i";;"i"Jt
ir',"
*inoingt-and
prevent motion
during
a
short
circuit
fault condition.
ThecurrentSenSorSprovideoperatingpoweraSwellas
"r""ni
level
data
lietetoie
wnen
tre
circurt
orgallr;1
;;ili"g
load
currents, Static
Trip
lll
trip urits
requrre
no
external connections
oi
"ontror
power to
perform
iheir
basic
overcurrent
protective
f
unctions'
Protective
Fault OPeration
il;t.ril;;i.;i;u
otiLt
o"t"tiption
of
the
process
forovercurrent
fault
orotection.
lhe
pio"".r
[or Ine
extended
protective
relaying
functions
is
very similar'
The
current
signals from
the
sensors are
converted to
digital
";[u*s-ov
i-resistor
network and analog to digital
conver-
i;.
fn/bti
in
the
trip
'"li
irt"
disital voltases are
stored
in
temporary memory and are used by
the^microprocessors
in
detecting and
procesling-o'etc"ient
conditions
and
in
metering,
The
orotectron
microprocessor reads the temporarily
stored
;i;:,5i;;il;"t u.i"""'p't"t
ir'";'
values
w'tn the set
or
;;Yr;;
"oiiJtpo^o'ns
to
the setting selected
bv the
use''
When
an
overcurrent
condition
is
detected'
the
micropro-
iu..o|.[.oti*ul."
begins to process the appropriate
protec-
l"tlr""tL".
During t6e
Iroc'essing
of
the protection
function'
the
microprocessor continues
to
monitor
the
incoming
cur-
rent
level
data lt tn"
ou"L*t"nt
condition
continues
until
thetrrocessingtscompletedandtheappropriatedelaytime
;;."";.;
I
itppi"s
command
is.tssued by
the
mtcropro-
;;;#" T;"
tripping"
command from
the..microproces-
sor causes an output signaf
io
be sent to
a
coil
in
the
tripping
actuator,
TripPing Actuator
When the
circuit
breaKer
is
closed'
the
tripping
actuator
is
held
* ;
"h";g;;
position
by a
permanent
magnet
The
output
;ig;rl
ilil-in6
trip uniiLnelgizes a coil
inside the acluator
causinq the
nagnetrc
ti'^
to
siitt
to
a
new
path
This releases
;h"*;i;;"; ;.;rgv
of
a
spting,
also
located
inside the actuator'
,.O"tte.
til
"i6rit
Ot"Ir''"'"Wh"n
the
circuit
breaker mecha-
nism opens,
tn" a"t'Jioi
is
automatically
reiurned
to
the
charged-and
rrero
posiliJn oy
a reset
mechanism A
second
coil inside
tfre
tripping'att'utdt
is
used
to
augment the holding
power
of
the permanenimagn-et
during
high short
circuit
con-
ditions
so
that
.truy
'ugn"tic
fietds witl nol cause unintended
;i";.;;t
;;mugn"ti'ition
while
the
trip
unit
is
in
short time
delay (US Patent issued)
Current Sensors
Tripping Actuator (bottom view)
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