GE AKR Series User Manual

Power
Circuit
Breakers,
GEI'86134
FALSE
TRIPPING
- BREAKERS
EQUIPPED
WITH
GROUND
FAULI
When
nuisance
tripping
occurs
on
breakers
equipped
with
the
Ground
Fault
trip
element,
a
p"onalte cause
is the existence
of a
false
"ground"
slgnaf .
As
indicated
by the
cabling
diagram
of
Fig.
26, each
phase
sensor
is connected
in series
with a
primary
winding
on
the
Ground
Fault
differential
lransformer.
Under
no-fault
conditions
on
3-wire
Ioad
circuits,
the currents
in these
three
windings
add
to zero
and
no
ground
signal
is developed.
This
current
sum
will
be
zero
only
i-t
all
three
sensors
have
the
same
electricaL
characteristics.
If
one
sensor
di-ffers
from
the others
(i.
e.,
differ-
ent
rating or
wrong
tap setting),
the
dilferential
transformer
can
produce
output
sufficient
to trip
the
breaker.
Similarly,
discontinuity
between
any
sensor
and
the
programmer
unit can cause
a
false
trip
signal.
If
nuisanc
e
tripping
is encountered
on any
breal<er
whose SST
components
have
previously demonstrated
satisfactory
performance
via
the
TAK-TS1
Test
Set,
the sensors
and
their connections
should
be
closely
scrutinized. After
disconnecting
the
breaker
from all
power
sources,
a)
Check
that
all
phase
sensors
are
the same
type
(ampere
range).
b) Ensure
that the
tap settings on all
3-phase
sensors
are
identical.
c)
Verify
that
the
harness
connections
to the
sensors
meet
the
polarity
constraints
indi-
cated by
the
cabling
diagram, i.e., white
wire
to
COMMON,
black
wire
to
TAP.
d)
On Ground
Fault
breakers serving 4-wire
loads, check that
the neutral
sensor is
prop-
erly connected
(see
cabling
diagramFig.
2?).
In
particular,
(1)
Verify
that
the neutral
sensor has
the
same rating
and
tap
setting
as
the
phase
sensors.
(2)
Check
continuity
between
tlle neutral
sensor
ald
its equipment-mounted
se-
condary
disconnect
block.
Also
check
for
continuity
from the breaker-mounted
neutral secondary
discormect block
through to the
female harness connector
(terminals
L and
N).
If
the breal<er's
lower
studs connect
to
the
supply
source, then the neutral
sen-
sor must have
its
LOAD
end connected
to the source.
Ensure
that the
neutral
eonductor
is
carrying only
that
neutral current
asso-
ciated
with the breaker's load current
(neutral
not shared
with other
loads).
e) If
the
precedingstepsfail
toidenti-ty the
prob-
Iem, then the
sensor resistances should be
measured.
Since
the
phase
and
neutral sen-
sors
are electrically
identical,
their
tap-to-
tap resistances
should
closely agree.
REPTACEMENT
OF CURRENT
SENSORS
Referring
to
Fig.
17,
remova!
of
individuat
SST
current sensors is
accomplished as
follows:
a) Disconnect
the
breaker
harness from the tap
terminal
board
(5),
removing cable
ties
as
necessary.
Unfastenthe terminal
board
from
the
breaker
base.
b)
At
the rear
of
the
breaker,
remove
the two
Allen
head
screws
(2)
to
separate the
stud
connector
(3)
from
the contact
pivot
block.
c)
Loosen
the clamping
bolt
(7)
and
remove
the
stud
connector.
Lift
out
the
sensor
and its
tap terminal
board.
NOTE:
To
prouide
more working
clearance
to adjacentaccessories,
i,t
may sometimes
be
necessary to
remoae the sensor stud
(8)
also.
Do
this
by remouing
its
foar
holdi,ng bolts, accessible
from
the rear of
the
breaker
(see
Fig. 20).
(3)
(4)
19

GE AKR Series Specifications

General

Brand	GE
Model	AKR Series
Category	Circuit breakers
Language	English