Corona & Infrared Camera Comparision PPT

advertisement
Ox Creek Energy Associates Inc
SDVeteranOB
Dan Ninedorf
Corona Technology Course Instructor & Co-Developer
Level II Infrared Technician
Electrical Power Engineering Tech
over 45 years of high voltage experience
over 20 years of IR-UV-Visible camera experience
- answers your question's series -
The first question typically is What Will Corona See That Infrared Will Not ?
--- Arrow keys to advance slide. -Copyright 2013 Ox Creek Energy Associates Inc
Corona Camera vs Infrared Camera
Under Construction  The following slides will show
where this is going as fast as
possible.
 Your questions are welcome,
 email: [email protected]

Corona Camera vs Infrared Camera





Daylight corona camera

Senses light photons in the
range 260-300nm, subject to
reflections on water droplets in
the air.

Corona (ultraviolet photon
detector image) overlaid onto
color visible image, in “real
time”.
The corona detector is slaved
to the Visible camera typically
thru at least part of the visible
cameras “zoom” range.
Corona cameras ”default field
of view” is typically at 100mm,
and “zoom” from there.




Infrared Camera
Electrical - Typically long-wave 8-12
micron (8,000-12,000nm)
Senses heat radiated from objects,
subject to reflections from sun, shiny
surfaces or holes.
Infrared image & may have visible image
camera.
Infrared cameras do not “zoom”, they
focus at a “field of view (FOV)”, then can
be adjusted to focus at a different
“distance” with same FOV.
Infrared cameras “default field of view” is
typically 35 to 50 mm lens, change lens
to “focus at a smaller or larger “field of
view”. Lens can cost thousands of
dollars..
Corona Camera vs Infrared Camera

Lets consider these statements.

A graph can show the light emission spectrum.

No single sensor can see all of the spectrum.




The Corona Camera sensor is much more sensitive then current
Infrared Camera sensors. With a daylight corona camera I have
seen the indication of corona across a mountain valley one mile
away.
Everything has a temperature and for our purposes can be seen
with an infrared camera.
Long-wave infrared is the choice for outdoor, low-emissivity
hardware that electrical inspectors look at, due to less solar
reflection which causes erroneous temperature readings.
Companies may select an emissivity standard to use for all
infrared scans, typically between 0.85 and 0.95 depending upon
the materials they look at and personal choice.
Corona Camera vs Infrared Camera





Lets consider these statements.
Some light sources emit across many wavelengths at different intensities at
different times (the sun).
Chemical sources block light in only discrete wavelengths, that are called
absorption bands, this can be used to locate gas leaks and identify specific
chemicals, such as SF6 gas leaks. A normal infrared camera is not filtered and
cannot isolate wavelengths to see these gases because other wavelengths “overpower” the missing signal in the absorption band.
Day-light corona cameras development was enabled because the ozone layer
surrounding the earth absorbs the sun light in the 260-300nm wavelengths making
these wavelengths on earth pitch black around the clock, except for mostly manmade light sources, such as fire, florescent lights, corona, arcing, arc welding,
which all change the state of the nitrogen in the air or emit photons visible in the
260-300 nm band.
Daylight corona cameras were developed to enable scanning of remote electric
transmission lines from helicopters, and because a helicopter can scan power
lines over crop fields or urban areas without disruption, getting stuck in mud, and
much quicker, a rough number can be 90 towers a day on flat land by helicopter
versus maybe10 from a vehicle. Scanning from a helo does not replace the need
to follow-up from the ground, to do in-plant surveys, R&D, distribution voltage, and
more.
Corona Camera vs Infrared Camera






Seeing corona is the first step, which requires a quality lowlight or day-light corona camera dependent upon application.
Understanding the probable causes of corona in that situation
(materials, shape, voltage, …) is the next step. The answer to
the question OK You found corona, what does it mean.
From experience deciding if that corona is detrimental and
what repair priority or monitoring is needed.
Corona can produce excessive noise resulting in complaints.
Arcing can produce radio/tv interference (RFI) for a mile around
that neither infrared or ultrasound can locate. But a daylight
corona camera can see from nearly a mile away.
Micro-Arcing (inside connectors) can occur that causes RFI
and corona that infrared cannot image.
Corona Camera vs Infrared Camera
So a corona camera images the ultraviolet light So an infrared camera images the
emitted during the change in state of nitrogen
in the air due to electrical field intensity or
during the initial burning of vegetation.
temperature of objects.
Electric current flow changes the
temperature of electrical equipment
and electronic devices.
The electric field intensity around energized
equipment can exceed the breakdown strength
When the temperature of electric
of air, when this happens corona starts.
equipment exceeds 20 to 50F above
The exact voltage to cause corona is dependent
ambient temperature (based upon
upon the shape of the object, the object's
standards) or when compared to the
proximity to other secondary objects, there
temperature of other phases in the
shape, applied voltage and polarity, the
circuit, preferred load is 40%
altitude, wind speed, ambient temperature,
conductor capacity or higher at less
humidity -primarily when condensing, when it
then 10mph wind.
can act like stepping stones in creating a flashSo it can be said that an infrared camera
over path, the same occurs when a
displays the temperature of object(s)
contaminated object is drying unevenly.
due to current flow in those object(s.)
So it can be said that a corona camera displays
when the relative voltage (electric field
intensity) on an object exceeds the relative
breakdown strength of air.
Corona Camera vs Infrared Camera


The MultiCAM developed by CSIR (now built
by UViRCO Technologies (Pty) Ltd) is the first
-and only- camera to combine the ability to
simultaneously image corona and infrared and
visible.
This is done by precisely overlaying two
images -one corona image overlaid onto one
infrared image -of the exact same Field of
View (FOV)- or with the push of one button
corona onto a visible image. This is done in
real time with a NTSC video output for
recording and image storage.
Corona Camera vs Infrared Camera






So at any time the MultiCAM has 3
image's or 3 video streams available for
viewing.
Using one push button the operator
selects corona overlaid onto infrared or by
pushing the button corona overlaid onto
visible.
Corona overlaid onto visible is common to
all daylight corona cameras.
Scanning with corona overlaid onto
infrared should find all problems.
Corona color, selecting a color not in the
infrared palette or not blending into the
clouds is better for contrast, easier to spot
problems.
Scan with corona gain at maximum until
an object of interest is located. Then
adjust the gain for the best image to tell
the story.
Corona Camera vs Infrared Camera

Corona (red blob's)
overlaid onto infrared
image

Corona overlaid onto
visible image
Corona Camera vs Infrared Camera

Corona at maximum
gain on infrared

Corona at maximum
gain on visible
Corona Camera vs Infrared Camera
In 2000,
The CoroCAM IV+
introduced daylight
corona cameras.
In late 1985,
The CoroCAM 504 became the world's most
sensitive corona camera, with it's patented
exclusive menu-selected low-light & daylight corona observing capability.
Corona Camera vs Infrared Camera

Corona on generator
winding bus bar.


Corona on post
insulator cement.
Corona creates porosity in cement,
moisture wicks inside, insulator
explodes when energized.
Corona Camera vs Infrared Camera

Corona on defective
NCI insulator & tree

Corona on defective
NCI insulator.
Corona Camera vs Infrared Camera

Infrared camera
see's isolated “hot
spots” in burnt areas.

Corona camera see's
direction of fire – new
burn.
Corona Camera vs Infrared Camera


Corona on a sprinkler
line hangar.

Corona on a cotter
pin.
Corona (nitric acid) particulate was falling on enclosures
and other insulators below, flash-over hazard.
Corona Camera vs Infrared Camera

Corona on / between conductors can
be caused by a conductor too small
for altitude and/or voltage, new or
scuffed conductor, or conductor
spacing.


Corona in the center of all insulator
strings is bad, and NCI corona is
usually over an arcing spot.
NCI corona will kill an insulator with
an expected life-span of 80 years,
maybe in 10 years.
Corona Camera vs Infrared Camera


This shows three corona problems:
frayed wire stub below pistol -grip
connector





Over-length bolts on saddle.
NCI insulator to hardware interface,
this will destroy the insulator, typically
within 10 years.
This shows corona on an:
undersize conductor,
conductor diameter too small for the
applied voltage,

conductor dragged over stones,

new conductor with “die grease”.
Corona Camera vs Infrared Camera
During training a corona
technician must learn what
can interfere with getting a
reliable image, reading of
corona.
The Corona Technology Course
provides this information in
video.
The ESKOM “Corona” manual
provides a text.
During infrared training,
4 days Level 1,
4 days Level 2
the technician learns
theory, what interferes
with imaging and to get
a best thermal image
from the camera in use.
Specific camera training
and refresher courses
Corona Camera training is also
are often required
a necessity to understand
annually by the
camera operation and corona.
certifying agent.
Corona Camera vs Infrared Camera
In the field The corona count is somewhat immaterial, but not to be ignored.
A high corona count can indicate arcing,
A corona blob constantly in one spot can indicate reflection or arcing.
A corona blob suspended over the top of one spot is likely internal arcing,
this can occur on NCI, substation PT's,..Not able to image with infrared.
The location of the corona is what matters,
If the corona is on an insulator material vs on hardware.
Is the corona causing a contamination build-up on an insulator, flashover
potential.
On metal that doesn't get washed by rain, corona produces nitric acid.
This is written to cover corona in substations, transmission lines,
switchgear, HV motors or generators.
Ox Creek Energy Associates Inc
SDVeteranOB
Dan Ninedorf
3120 S Business Dr, Sheboygan, WI 53081 USA
Tel/Cell: 800-531-6232 Email: [email protected]
www.specialcamera.com
www.corona-technology-course.com
- answers your question's series -
The first question typically is What Will Corona See That Infrared Will Not ?
Copyright 2013 Ox Creek Energy Associates Inc
Download
Related flashcards

Encodings

15 cards

Sensors

21 cards

Computer hardware

24 cards

Display technology

31 cards

Apple Inc. hardware

40 cards

Create Flashcards