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Electrical
systems
are
among
the
most
valuable
assets
in
your
plant
and
can
have
the
biggest
impact
on
your
bottom
line.
Their
production
and
management
cost
is
high,
and
failures
almost
always
lead
to
catastrophic
losses.
Electrical
systems
are
being
operated
at
higher
levels,
even
while
systems
are
aging—which
affects
both
the
life
and
the
reliability
of
the
assets.
Today’s
asset
managers
are
facing
the
increased
challenge
of
maximizing
their
aging
electrical
infrastructure
with
fewer
qualified
technical
in-house
resources,
stricter
regulatory
requirements
for
worker
safety,
and
shrinking
maintenance
budgets.
Advances
in
technology,
including
the
use
of
Partial
Discharge
Testing,
are
giving
asset
managers
new
approaches
to
achieve
improved
reliability
and
performance
of
critical
electrical
assets.
What
is
Partial
Discharge
(PD)?
Partial
discharges
are
small
electrical
sparks
that
occur
within
the
insulation
of
medium
and
high
voltage
electrical
assets.
Each
discrete
partial
discharge
is
the
result
of
an
electrical
breakdown
of
an
air
pocket
within
the
insulation.
These
discharges
erode
insulation
and
eventually
result
in
insulation
failure.
According
to
the
National
Fire
Protection
Association
(NFPA
70B),
the
leading
cause
of
electrical
failures
is
insulation
breakdown.
The
National
Electrical
Code
(NEC)
states
that
these
partial
discharges
are
the
first
indication
of
insulation
deterioration.
Research
from
the
IEEE
Gold
Book,
Table
36,
indicates
that
cables,
switchgear,
and
transformers
suffer
the
greatest
losses
from
insulation
failure.
For
more
than
50
years,
companies
have
performed
Partial
Discharge
Testing
on
electrical
assets
as
part
of
ongoing
predictive
maintenance
programs.
Data
obtained
through
Partial
Discharge
Testing
and
Monitoring
can
provide
critical
information
on
the
quality
of
insulation
and
its
impact
on
overall
equipment
health.
Because
partial
discharge
activity
is
often
present
well
in
advance
of
insulation
failure,
asset
managers
can
monitor
it
over
time
and
make
informed
strategic
decisions
regarding
the
repair
or
replacement
of
the
equipment.
These
predictive
diagnostics
help
companies
to
prioritize
capital
and
MRO
investments
before
an
unexpected
outage
occurs.
Partial
discharge
testing
results
can
help
predict
future
performance
and
reliability
of
critical
assets,
including:
l
Cables,
splices,
and
terminations
l
Power
transformers
and
bushings
l
Switchgear
l
Motors
and
generators
Failures
are
not
limited
to
service
aged
equipment.
Acceptance
testing
on
newly-installed equipment
builds
in
reliability
right
from
startup.
Acceptance
Testing
can:
l
Verify
original
manufacturers
test
data
and
identify
damaged
insulation
that
occurred
from
l
improper
installation,
poor
design,
and/or
poor
workmanship
during
or
after
installation.
l
Identify
premature
failures
and
capture
baseline
data
to
trend
asset
health
over
the
asset’s
l
life
cycle
to
ensure
maximum
return
on
investment.
Integrated
Partial
Discharge
Solutions
HVM’s
integrated
Partial
Discharge
Testing
and
Monitoring
solutions
include
both
online
and
offline
testing
as
well
as
periodic
and
continuous
monitoring
of
your
electrical
assets.
Depending
on
your
specific
operating
requirements
and
application,
HVM
can
customize
a
program
to
best
fit
your
needs.
Choose
from
the
following
solutions:
l
Online
Partial
Discharge
Testing
l
Handheld
Survey
l
Periodic
Partial
Discharge
Testing
l
Continuous
Online
Monitoring
l
Ultrasonics
l
Offline
Partial
Discharge
Testing
l
Tan-Delta
l
Very
Low
Frequency
Testing
(VLF)
Online
Partial
Discharge
Testing
Online
testing
is
performed
while
the
equipment
is
energized
at
normal
operating
voltages.
The
testing
is
conducted
during
real
operating
conditions,
under
typical
temperature,
voltage
stresses,
and
vibration
levels.
It
is a
nondestructive
test
and
does
not
use
over
voltages
that
could
adversely
affect
the
equipment.
Online
Partial
Discharge
Testing
is
relatively
inexpensive
compared
to
offline
testing
that
requires
interruption
of
service
and
production.
For
critical
facilities
that
operate
24x7,
this
is
the
best
solution
for
identifying
insulation
condition.
HVM
conducts
online
periodic
testing
using
a PD
Surveyor
and
a
Portable
PD
test
unit
with
noninvasive
sensors.
The
PD
Surveyor
is
the
first
multi-purpose
handheld
device
able
to
conduct
the
initial
pre-screen
to
identify
the
critical
equipment
for
testing.
Typically
only
5 to
10%
of
medium
and
high
voltage
assets
will
have
significant
levels
of
PD
activity.
This
prescreening
will
provide
the
required
data
to
develop
an
overall
test
plan
to
ensure
focus
on
the
right
assets,
minimizing
unnecessary
spending.
The
pre-screen
also
provides
a
safety
check
prior
to
opening
panels
or
performing
work.
Once
the
assets
are
prioritized,
HVM’s
test
engineers
conduct
the
periodic
PD
measurements
using
non-invasive,
calibrated
PD
sensors
including
High
Frequency
Current
Transformer
(HFCT)
sensors,
Transient
Earth
Voltage
(TEV)
sensors,
or
Airborne
Acoustic
sensors.
These
sensors
are
inductively,
capacitively,
or
acoustically
coupled
to
the
equipment
to
provide
online
PD
testing
while
the
equipment
remains
energized.
Each
point
of
attachment
is
tested
for
just
a
few
minutes,
enabling
a
large
number
of
assets
to
be
tested
quickly
and
easily.
The
technology
can
also
provide
conventional
offline
partial
discharge
measurements
in
accordance
with
International
Electrotechnical
Commission
(IEC)
requirements.
HVM’s
advanced
test
application
captures
the
partial
discharge
signals
synchronously
across
the
60Hz
power
cycle,
allowing
the
test
engineer
to
observe
phase-related
patterns
of
discharge—online
and
in
real-time.
HVM’s
analysis
application
provides
an
automatic
PD
“criticality”
level
based
on
magnitude
and
number
of
PD
pulses
per
power
cycle.
The
PD
reader
uses
easy-to-understand,
knowledge-based
methods
to
provide
PD
pulse
discrimination
regarding
source
of
partial
discharge
(cable,
switchgear,
etc.)
while
automatically
presorting
electrical
“noise”
pulses.
The
application
also
includes
an
automatic RF
noise
reduction
function.
Permanently
Mounted
Sensors
For
“hard
to
access
areas”
or
areas
that
pose
a
safety
concern,
you
can
use
permanently
mounted
sensors
for
periodic
online
PD
detection.
These
HFCT
sensors
are
installed
by
HVM
engineers
and
remain
on
the
equipment
for
online
access
and
diagnostic
information.
Often,
these
sensors
must
be
installed
during
an
outage
or
plant
downtime.
Once
installed,
no
further
outage
or
disruptions
are
required
for
online
testing.
Periodic
Partial
Discharge
Testing
Sometimes,
you
may
need
to
conduct
continuous
monitoring
over
a
short
period.
A
portable
PD
Monitor
can
be
used
to
perform
continuous
monitoring
from
one
hour
up
to
three
months.
Through
continuous
monitoring,
HVM
will
trend
your
assets
over
a
longer
period
of
time
to
provide
a
more
accurate
assessment
and
recommendation.
This
solution
is
less
expensive
than
installing
a
permanently-mounted
PD
monitoring
system.
Continuous
Online
Monitoring
For
your
most
critical
assets
that
have
demonstrated
high
levels
of
partial
discharge,
including
those
that
are
nearing
the
end
of
their
life,
continuous
online
PD
monitoring
may
be
the
answer.
Measure
and
analyze
data
on
your
electrical
assets
and
provide
remote
access
via
LAN
or
modem
to
deliver
continuous
and
accurate
data
on
the
condition
and
capability
of
the
equipment.
Continuous
monitoring
will
also
provide
timely
alerts
to
maintenance
and
will
identify
impending
failures
before
an
unplanned
shutdown
occurs.
Ultrasonics
When
problems
occur
in
medium
and
high
voltage
electric
equipment,
such
as
partial
discharge
and
corona,
it
will
produce
sound
waves
that
can
be
detected
by
Ultrasonic
testing.
Performed
without
disrupting
plant
or
facility
operations,
Ultrasonic
testing
is a
non-destructive,
noninvasive
predictive
maintenance
tool.
Because
it
maintains
insulation
integrity,
it
is
commonly
employed
in
applications
such
as
cable
terminations,
switchgear,
busbars,
and
transformers.
Ultrasonic
measurement
is
most
powerful
on a
comparative
basis
and
can
significantly
increase
the
reliability
of
partial
discharge
detection
when
used
with
other
HVM
partial
discharge
testing
technologies.
Offline
Partial
Discharge
Testing
Offline
Partial
Discharge
Testing
offers
a
significant
advantage
over
other
technologies
because
of
its
ability
to
measure
the
cable
system’s
response
to a
specific
stress
level
and
predict
its
future
performance
without
causing
a
fault.
Offline
testing
is
also
known
for
its
ability
to
pinpoint
the
exact
defect
location
on
field-aged
equipment,
enabling
the
asset
manager
to
accurately
plan
for
maintenance
and
repair.
The
challenge
with
offline
testing
is
that
the
equipment
must
be
taken
offline
and
out
of
service.
Offline
testing
is
also
commonly
used
in
acceptance
testing
on
newly-installed
cables.
When
deenergization
is
preferred,
HVM
can
conduct
offline
testing
as
part
of
your
predictive
maintenance
program.
Tan-Delta
Testing
Dissipation
Factor
(Tan-Delta)
is
one
of
the
most
powerful
offline
nondestructive
diagnostic
tools
used
to
monitor
the
condition
of
extruded
cable
insulation.
Capacitance
and
Tan-Delta
values
from
new
insulation
are
used
as
benchmark
readings.
By
comparing
periodic
readings
of
the
capacitance
and
Tan-Delta
of
your
insulating
material
with
the
benchmark
readings,
you
can
measure
the
deterioration
of
the
insulation,
predict
the
life
expectancy,
and
plan
maintenance
and
repairs
before
an
unexpected
outage
occurs.
A
significant
advantage
of
Tan-Delta
testing
is
the
ability
to
detect
water
trees—a
major
source
of
insulation
failures
in
aged,
extruded
cables.
Tan-Delta
testing
can
be
performed
during
the
manufacturing
process.
The
testing
frequency
depends
on
the
rate
of
change
of
the
insulation
quality,
history
of
past
failures,
environmental
conditions,
etc.
High
levels
of
environmental
moisture,
elevated
temperature,
and
chemicals
or
pollution
may
require
more
frequent
testing.
HVM’s
test
engineers
can
help
you
evaluate
your
requirements
and
establish
a
program
that
best
meets
your
needs.
Very
Low
Frequency
Testing
(VLF)
VLF
AC
Hipot
testing
was
developed
in
the
early
1980s
as a
substitute
for
DC
Hipot
testing.
DC
Hipot
testing
is
no
longer
an
acceptable
test
method
for
field
aged
extruded
cables
because
of
its
destructive
nature
and
inability
to
determine
insulation
quality.
Although
VLF
testing
is
primarily
used
to
perform
hipot
or
withstand
testing
in
cables,
it
is
also
suitable
for
testing
transformers,
switchgear,
rotating
machines,
and
other
electrical
assets,
and
is
frequently
used
as a
voltage
source
for
offline
testing.
A
VLF
hipot
test
is a
go/no-go
test
and
is
not
a
diagnostic
test,
but
is
one
of
the
best
ways
to
check
the
AC
integrity
of
an
electrical
asset
to
determine
a
pass
or
fail
result.
Similar
to
offline
partial
discharge
testing,
the
challenge
of
this
test
is
that
the
equipment
must
be
taken
out
of
service.
Maximize
Uptime
Partial
discharge
testing
plays
a
critical
role
in
determining
the
health
of
your
electrical
assets
and
ensuring
maximum
uptime.
It
also
provides
asset
managers
with
the
critical
information
to
target
maintenance
resources
to
the
areas
that
require
the
most
attention.
Depending
on
your
specific
operating
requirements
and
application,
HVM
can
help
you
develop
and
implement
the
right
combination
of
technology,
online
or
offline,
to
meet
your
maintenance
requirements.
Improve
operational
efficiency
and
worker
safety
by
working
with
the
experts
at
HVM.
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