Infrared thermography

OVERVIEW
 INTRODUCTION
 BASIC INFRARED THEORY
 INFRARED INSPECTION EQUIPMENT
 BLOCK DIAGRAM OF IR IMAGER
 IR THERMOGRAPHY IN ELECTRICAL
INSPECTION
 IR MAINTENANCE TECHNIQUES
 PROS AND CONS
 CONCLUSION
 REFERENCES

INTRODUCTION
 Infrared thermography is a proactive troubleshooting and
predictive maintenance tool.
 It is the process of acquisition and analysis of thermal
information from non-contact thermal imaging devices.
 Thermal or infrared energy = Light which is not visible because
its wavelength is too long to be detected by the human eye: it's
the part of the electromagnetic spectrum we perceive as "heat".
 Thermography = The use of an infrared imaging and
measurement device to "see" and "measure thermal energy
emitted from an object.
 Infrared testing is essentially a non-invasive, non-destructive
inspection process that uses thermography cameras.
 These devices gather temperature signatures that lie far
beyond the range of visible light.

ELECTROMAGNETIC
SPECTRUM
 The electromagnetic spectrum is the distribution of
electromagnetic radiation according to energy. It is
the range of all possible frequencies
of electromagnetic radiation.
 The electromagnetic spectrum extends from below the
low frequencies used for modern radio
communication to gamma radiation at the short-
wavelength (high-frequency) end, thereby covering
wavelengths from thousands of kilometers down to
a fraction of the size of an atom.

THERMAL SCIENCE
 Heat is thermal energy associated with temperature-dependent
motion of particles
 Photography can be described as writing with Light
 Thermography can be described as writing with Heat
 Heat Transfer Modes:
 Conduction
 Convection
 Radiation
 EMISSIVITY
 Emissivity is a term representing a material's ability to emit thermal
radiation
Conduction
Radiation
Convection

PRINCIPLE OF IR
THERMOGRAPHY
 Since infrared radiation is emitted by all objects based on
their temperatures, according to the black body radiation law,
thermography makes it possible to “see” one’s environment
with or without visible illumination.
 The amount of radiation emitted by an object increases with
temperature; therefore thermography allows one to see
variations in temperature.
 All objects emit a certain amount of black body radiation as a
function of their temperatures. The higher an object’s
temperature is the more infrared radiation as black-body
radiation it emits.
 A special camera can detect this radiation in a way similar to
an ordinary camera does visible light.
 It works even in total darkness because ambient light level
does not matter.

Visual Image Thermal image
Thermal Imaging with an
infrared camera.
“ Paints a different picture.”
These two glasses
visually appear the
same.

CONSTRUCTION
OVERALL EQUIPMENT SETUP
9

COMPONENTS FOR IR
IMAGER
 Detector
There are two options for a thermal imaging detector, cooled and uncooled,
both types of detector absorb infrared energy which in turn affect the detectors
electrical properties to produce an image.
 These detectors use narrow gap semiconductors to offer high sensitivity to
infra-red radiation. These semiconductors have to be housed in a vacuum
sealed case and cryogenically cooled (typically to below a temperature of
110K).
 Lens
The Lens is not made out of glass like the lens of a normal
CCTV camera. The properties of glass mean that it does not
transmit infrared radiation very well and would be an
impractical lens material for thermal imagers. Instead
Germanium is used which is a naturally occurring chemical
element that is transparent to IR Radiation (that is that it will
allow IR Radiation to pass through it).

.
 SENSOR:
 The ML8540 is a medium-
resolution (approximately 2,000
pixels) infrared image sensor
that allows noncontact
temperature measurement of
an object and easy obtaining of
thermal images.
 The ML8540 receives infrared
rays from an object at 48×47
(2,256) pixels resolution,
converts them into voltage
through a thermopile, and
selects pixels in accordance
with external CPU clocks to
output signals.

IR THERMOGRAPHY IN
ELECTRICAL INSPECTION
 The infrared electrical testing allows for inspection of a large
amount of electrical equipment in a short time as opposed to
the alternative method of physically inspecting and tightening
electrical components.
 The infrared electrical systems survey locates faulty
electrical items not generally found during a physical
inspection.
 The infrared electrical systems survey locates problems
before they lead to an unscheduled outage, equipment
damage or a fire. Today’s facilities engineers are avoiding
costly expenses every year with infrared electrical surveys.
 Infrared thermography testing is non-contact and
nondestructive testing (NDT), there is no need to interrupt
system production.

MAINTENANCE OF
EQUIPMENT BY IR
THERMOGRAPHY
 Electrical switchgear and panels are the lifeblood
of a data center. Without it, equipment failure is
immediate.
 If there is dual power or utilizing redundant power
sources, anytime we switch over power from
primary to a backup power source infrared scan
the switchgear and backup electrical panel boards
and branch circuits for excessive heat.
 Testing while under load will tell us if there has
been any degradation in the system components
that could lead to future equipment failure and a
possible outage.

CHECKING OF VARIOUS EQUIPMENTS
 ELECTRICAL PANELS:
Open and scan the electrical panel and look for hot
spots. Loose or week connections between
breakers and the main panel bus and other
deficiencies including overloaded circuits, load
imbalances, harmonic problems and defective
electrical components can all contribute to a thermal
scan heat signature.
 Anytime someone needs to access an electrical
panel, power distribution unit or remote power
panel, they should infrared scan the branch circuits
and breakers for excessive heat. Even if you find
yourself in an electrical panel every week, it only
takes a few seconds to scan and determine if a
problem exists.

.
 CIRCUIT BREAKERS:
 This 2,000A breaker has an obvious over
temperature condition on the terminal. A
high resistance or loose bolted connection
is causing this problem. Early detection and
correction of this problem will prevent a
major plant-wide power outage. The
advanced warning from the thermographic
image will also prevent a significant
unplanned business interruption.
 Bad Fuse Clip
 This fuse clip, on the load-side of the C-
phase, has lost its tension. The loose
spring tension creates a high-resistance
joint that produces excessive heat .
Heating at this fuse clip can also cause
many nuisance blown fuses due to the
internal fuse element heating from this
local bad connection.

.
 Loose Wire
The load-side wire on this control
panel contactor was not installed
properly. The wire was cut back
and properly re-terminated to allow
for continued plant production.
 Power Feed from Plant
This is the connection point between a
renewable resource power plant and
the local utility grid. A medium-voltage
cable termination is showing excessive
heat compared to the other two
phases. Since this connection is
high atop a utility pole, it would be hard
to smell or see any smoke if it
developed. It is also far away from the
areas where anyone normally performs
work.

. Power Plant
 This power plant has multiple problems with overheating
terminations on the network. A single thermographic image
can see all of the hot spots in one viewing and at a safe
distance away from the medium- or high-voltage
equipment. The criticality of any system is based on the
consequences of a failure. In a manufacturing plant failure and
outage, only one customer is typically affected. On the other
hand, when a utility electrical connection fails, entire
geographic areas can be affected by the resulting outage.

.
 Transformer Connection
 These three single-phase
transformers are connected to provide
a 3-phase service to a manufacturing
facility. You can see that two of the
secondary terminal connections are
overheating, a failure at this point in
the system means a total unexpected
plant shutdown. If the production
equipment is running at the time the
termination fails, the 3-phase
equipment will single-phase and is
likely to cause additional production
equipment damage beyond the failed
termination.

. Solar Panel
 This is a thermographic image of a solar module. Many individual solar
cells make up one solar module. The solar cells are the squares within the
grid of dots on the module. You can see the cells that are giving off a much
higher heat signature. The hotter cells are not supplying energy to the grid
system because they are locally dissipating their energy as heat. As new
renewable energy technology advances, new uses are found for the
thermographic camera. Viewing the thermographic image needs to be
combined with the wisdom of a seasoned thermographer to properly
interpret and diagnose conditions.

PROS AND CONS
 PROS
 Low Power
Requirement
 Low Circuitry Cost
 Portable
 Higher Security
 CONS
 Blocked By Materials
 Short Range
 Slow Data Transmission

CONCLUSION
 Infrared surveys are a powerful, versatile, and highly
accurate diagnostic tool for uncovering a wide range
of problems in electrical systems.
 Infrared monitoring and analysis has the widest
range of application (from high- to low-speed
equipment), and it can be effective for spotting both
mechanical and electrical failures.
 It also requires minimum skills for analysis.
 In recent times thermography is being used in
firefighting, law enforcement, industrial applications,
security, transportation, medical and many other
industries.
 “To See More – Is to Know More”.

REFERENCES
25
Infrared thermography: An optical method in heat transfer and fluid flow
visualisation, by T. Astarita, G. Cardone, G.M. Carlomagno University`, Italy
Lucier, Ronald; “How to Guarantee Your Failure as an Infrared
Thermographer“; Proc. InfraMation; 2002.
Leonard Ken, Madding Robert P. and Orlove Gary L “Important measurements
that support IR surveys in substations” Proc. InfraMation; 2002, pp 19-25.

Infrared thermography

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