06
NWC1 Series Self-healing Low Voltage Shunt Capacitors
Table
7
Analysis
and
Troubleshooting
of
Faults
No
.
Faults
Cause
analysis
Troubleshooting
method
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
=
Uc
/
UN
×
IN
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
case
cracks
,
etc
.
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
end
.
See
3
.
3
.
2
for
harmonic
suppression
measures
.
5
Sometimes
there
is
buzzing
sound
in
the
cabinet
during
operation
.
There
is
harmonic
current
passing
through
the
capacitor
.
User
must
take
harmonic
suppression
measures
if
the
harmonic
current
is
too
big
(
same
as
4
)
6
There
is
significant
current
increase
when
adding
a
capacitor
into
a
group
.
Either
abnormal
power
frequency
resonance
(
underloading
),
or
harmonic
current
amplification
or
there
is
resonance
.
Same
as
4
7
Slight
deformation
occurs
to
the
capacitor
case
after
the
capacitor
has
been
used
for
a
period
of
time
,
and
no
current
can
be
detected
.
Long
-
term
overtemperature
or
overcurrent
operation
of
the
capacitor
which
cause
self
-
healing
breakdown
of
internal
components
that
generates
gases
and
increases
internal
pressure
.
When
the
overpressure
protector
breaks
,
slight
deformation
can
occur
to
the
capacitor
case
.
Use
heat
dissipation
measures
to
lower
the
ambient
operating
temperature
of
the
capacitor
.
Select
products
with
higher
rated
voltage
.
Harmonic
suppression
measures
are
the
same
as
described
in
4
.
9
Warranty
Period
,
Environmental
Protection
and
Law
&
Regulations
9
.
1
Warranty
period
The
warranty
period
of
the
product
is
30
months
from
production
(
delivery
)
date
if
the
product
is
kept
under
normal
storage
conditions
and
the
package
or
the
product
itself
is
in
good
condition
.
If
the
warranty
period
has
expired
,
please
inspect
the
product
and
make
sure
it
meets
all
the
requirements
before
installing
and
using
the
product
.
The
following
circumstances
are
not
within
the
scope
of
warranty
(
excluding
repair
or
replacement
):
