Siemens Static Trip III - Page 36

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Testing
One
other major
difficulty
with
primary
current testing
is related
to the
duty cycle
limitation
of
the circuit
breaker
and current
sensor.
A
properly
operating
tripping
system will
be self-
protecting
from
thermal
damage
up to
the circuit
breaker
short
time
and interruption
rating,
providing
that
the duty
cycle
applicable
for each
rating is
not
exceeded.
The standard
duty
cycle
for
the short
time rating
as demonstrated
per
ANSI
C37
50
is
0.5
Seconds
On, 15
Seconds
Off followed
by another
On
period
of 0.5
Second.
The
On
intervals
are too
short to read
the
ammeter
on the
current source,
For
the instantaneous
interruption
rating
each
of the
On intervals
are reduced
to
approximately
50
Milliseconds.
Because
of this, calibration
of
the
trip device
high range
settings
cannot
be accurately
done
with
primary
current.
The
calibration
can
be verified
safely
at the lower
settings
and
"operation
only"
verified
at the higher
set
points.
CAUTION:
lf
the
duty
cycle limits
are
exceeded
during
testing,
the
circuit
breaker
or current
sensor
as
well
as the
trip device
may
be damaged.
Between
tests, the
unit
must
r'emain
OFF long
enough
to allow
the
current sensor
to
cool. ln
addition,
if
there is
a
fault
in
the system,
the breaker
may not
operate within
its rated
time,
and the
system will
not
be self
protecting.
Therefore
to
properly
protect
the tripping
system from
potential
damage
and
still assure
proper
operation,
the
following procedure
is recommended.
lf the
breaker
has
a
ground
fault
sensing
trip
device
connect
a
jumper
between
terminals 4
and
5 of the trip
device,
1
Apply
to one
pole
of the
circuit
breaker
an input
current of
one half
the
current
sensor rating
and measure
the trip
device
power
supply voltage,
This
voltage
can be mea-
sured
with
the negative
lead
of the voltmeter
on Pin I
or
2
of the
15
pin
connector.
The
positive
lead
is
terminal block
number
7,
the red lead
of
the actuator.
lf this voltage
exceeds
I I Volts
with half
rated
current
supplied, it
can be
assured
that the wave
shape
distortion
can
be disregarded
except
for its
possible
effect
on the
ammeter indication,
Test
all
three
poles
of
the breaker
in a
similar manner,
this
establishes
that
the device
power
supply
circuits are work-
ing
2.
Set the long
time current
setting
to the .5
position.
Slowly
increase
the current
from zero
while
watching
the long
time
pickup
LED.
Pickup
should
occur
at one-half
the current
sensor rating
with
a
tolerance
of minus zeto
lo
plus
20
percent,
not
including
any ammeter
error. Pickup
is
the
lowest
current
at which
the LED
remains
illuminated,
Repeat
for
all
three
poles
of
the circuit
breaker.
This
proves
the
input
circuits
are
all working,
When
the
pickup
indication
is
present,
the long
tlme
circuittiming
element
is released
and
the device
will
time out
on LONG
TIME.
Repeat
calibration
check
on the other
long
time current
settings
as desired.
3. Set long
time current
setting
on
.5,
long time
delay on 3.5,
short time
pickup
and
jnstantaneous
on 12
Set the inpul
current equal
to the
current sensor rating.
Remove
and
reapply
the
power,
allow the
device to time
out and trip the
breaker.
The time
delay should meet
the
published
curves
for
the device
being tested.
Repeat for
all
long
time
bands.
Note
that the
Static Trip lll long
time circuits
respond to
the
RMS value
of the input
current,
and depending
on the type
of ammeter
being
used the times may
all appear
to be
longer
than
expected. lf
the test set has
an RMS responding
ammeter
the
time values
should check
properly.
4.
Set
instantaneous
at 2, short
time
pickup
at
12,
long time
delay
on
its
maximum
of 30. The
breaker
should trip
instantaneous
at twice the
current sensor rated
current with
a tolerance
of minus
zero
lo
plus
20
percent.
Repeat
for all
three
poles
of the breaker.
5
Set short
time
pickup
at 2, instantaneous
at 12, long
time
delay
on its maximum,
and
short time
delay on minimum
of
08.
Set long
time current
setting .5.
Slowly
increase
the
current. The
breaker
should trip
at the current
sensor rated
current with
a tolerance
of mlnus zero
to
plus
20
percent,
The
time delay
circuit
can allow the
current to increase
after
tripping
has
been initiated,
so the rate
at
which
the current
is
increased
must
be limited
to
prevent
"overshoot."
6 With the
same settings
as in
step 5, adjust
the supply
current
to
3 times the
current sensor rating,
Apply
the
current
and observe
the tripping
time, Test
allf
ive
shorttime
delay
bands. Note if
the device
contains Zone lnterlocking,
a Zl
input
signal must
be supplied
or the Zone lnterlock
switch
moved
to the
"out"
position
in order
to test other than
the minimum
time
delay band.
7. lncrease
both instantaneous
and short
time
pickup
to
12,
set the long
time delay
on 3.5, long
time current setting
on
.5 Adjust
the supply
to twice
current sensor rating.
Apply
this current
and
observe tripping
time. Test
at the same
current for
all
long
time
delay bands. Verify
that they meet
the
published
values.
Other values
of current
can be tested
if
overheating
is
prevented.
8. The
operation
of the
Short Time l,t ramp,
and time
delay
bands can
also be checked as desired.
9. lf the
device has
ground
fault
tripping, remove
the
jumper
from
terminals
4 and
5. Set
Ground
Fault
pickup
on 60,
increase
the supply
current from zero,
verify that
the
ground
circuit trips
the breaker
aI60% with
a tolerance of
plus
or minus
10%
of the
Ground Sensor rating.
Lower
settings
can be tested.
Depending
on the amount
of
waveshape
distortion there
may not be
enough
power
to
trip
the breaker
at the lowest
available
ground
fault
pickup
value
with no
other
phase
currents.
l0.To
demonstrate
operation at normal
control
settings, reset
all controls
to the
desired values,
set current
to a high
enough
value
to definitely
cause tripping,
apply
current,
and verify
that
tripping
does occur
as expected.
34