06
Analysis
and
Troubleshooting
of
Faults
Table
7
Analysis
and
Troubleshooting
of
Faults
NWC5/NWC6 Series Self-healing Low Voltage Shunt Capacitors
of
the
capacitor
and
can
cause
damage
to
other
components
and
conductors
in
the
cabinet
due
to
overload
.
7
.
2
Maintenance
during
operation
Tighten
the
terminal
screws
of
the
capacitor
on
a
regular
basis
(
once
half
a
year
)
to
prevent
poor
contact
.
Remove
dust
and
greasy
dirt
also
.
User
should
pay
close
attention
to
the
cabinet
and
replace
any
damaged
capacitor
in
time
if
any
under
-
compensation
of
power
factor
occurs
due
to
significant
capacitance
drop
(
50
%
current
decrease
),
otherwise
it
may
lead
to
penalty
.
If
all
the
capacitors
are
operating
and
in
good
condition
but
the
power
factor
still
cannot
meet
requirement
,
user
must
add
capacity
in
time
to
ensure
the
automatic
cycle
operation
of
the
capacitors
.
7
.
3
Service
cycle
User
should
determine
the
service
cycle
based
on
the
application
conditions
,
the
recommended
service
cycle
for
cabinet
is
once
half
a
year
.
7
.
4
Maintenance
for
long
-
term
idle
If
the
capacitor
has
been
idled
for
one
year
or
longer
,
please
check
if
its
capacitance
value
is
within
the
allowable
deviation
range
(-
5
%~+
8
%);
conduct
pole
-
to
-
case
voltage
withstand
test
again
(
apply
AC
3kV
for
5
seconds
);
or
use
megameter
to
test
if
the
insulation
resistance
between
the
three
phase
terminals
and
the
case
is
larger
than
100M
Ω
before
using
the
product
.
7
.
5
Storage
conditions
,
storage
period
and
precautions
The
smart
capacitor
should
be
stored
in
a
dry
and
well
-
ventilated
room
and
protected
from
rain
,
moist
,
chemicals
and
dust
.
The
maximum
storage
period
of
the
product
is
36
months
.
Do
not
put
the
smart
capacitor
or
its
package
directly
on
the
floor
.
1
The
measured
current
of
a
newly
connected
capacitor
is
much
smaller
than
the
rated
current
on
its
nameplate
(
same
for
multiple
capacitors
).
If
a
capacitor
with
higher
rated
voltage
is
connected
to
380V
grid
,
the
actual
output
current
will
be
much
smaller
,
which
is
normal
.
There
is
nothing
wrong
with
the
capacitor
,
it
is
just
derated
.
User
should
determine
the
status
of
a
capacitor
based
on
its
measured
capacitance
value
(μ
F
).
The
actual
operating
current
IC
=
U
c
/
U
N
×
I
N
2
The
current
of
the
capacitor
is
closed
to
rated
current
when
it
is
first
put
into
operation
,
but
the
current
drops
after
a
period
of
time
.
The
current
drops
as
the
capacitance
value
of
the
capacitance
decreases
.
There
are
several
reasons
for
capacitance
decrease
such
as
improper
use
,
large
harmonic
or
quality
defect
.
Find
out
the
reason
and
solve
the
problem
.
User
must
replace
the
capacitor
if
the
capacitance
value
drops
below
50
%.
3
The
terminal
screws
of
the
capacitor
generate
heat
or
even
turn
into
black
during
operation
.
The
wire
nuts
are
loose
or
not
tightened
properly
during
installation
.
If
the
nuts
are
tightened
properly
,
the
reason
might
be
long
-
term
overcurrent
due
to
harmonic
current
amplification
in
the
grid
.
Tighten
the
nuts
,
replace
nuts
,
flat
gaskets
,
elastic
washer
if
necessary
.
4
The
fuse
in
branch
circuit
blows
frequently
(
or
miniature
circuit
breaker
trips
frequently
);
the
CJ19
contactor
fuses;
the
current
-
limiting
resistance
burns
frequently;
the
surface
of
XD1
current
-
limiting
reactor
These
symptoms
are
typical
when
the
grid
harmonic
is
too
big
or
there
is
intermittent
resonance
in
the
grid
.
Conduct
grid
harmonic
test
or
check
if
there
are
harmonic
sources
such
as
frequent
converter
,
rectifier
,
intermediate
frequency
furnace
or
electric
-
arc
furnace
installed
at
load
No
.
Faults
Cause
analysis
Troubleshooting
method
