This document discusses infrared thermography and its applications for electrical systems. It begins with an overview of infrared basics, heat transfer mechanisms, and the electromagnetic spectrum. It then discusses how infrared thermography can be used to identify poor electrical connections, which can improve power quality and reliability by reducing risks of fire and unplanned outages. Specific examples shown include detecting high temperatures at fuse clamps, loose neutrals, and inductive heating patterns that indicate issues like loose connections on busbars. The document emphasizes that infrared thermography provides a generally non-invasive way to prioritize maintenance and safety inspections of energized electrical equipment.
4. National Fire Protection
Association
The National Fire Protection Association (NFPA) was
established in 1896 by concerned losses due to fires.
A primary cause of industrial fires and losses, as well
personal injury accidents, over the last five decades is
related to electricity.
NFPA recommends that “routine infrared inspections
of energized electrical systems should be performed
annually.
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5. Case for Using Infrared
Generally Non-Invasive Process (Safety)
Improve Power Quality by Identifying Poor Electrical
Connections (Voltage Drop Issues)
Improve Power Quality by Identifying High Neutral
Currents
Reduced Risk of Unplanned Outages (Reliability)
Reduced Risk of Fire (Insurance Discounts)
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13. Electromagnetic Spectrum
Light comprises only a small portion of the entire
electromagnetic spectrum.
Most of the electromagnetic spectrum is invisible to
the human eye.
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14. Above Absolute Zero
All objects emit infrared above absolute zero
The warmer the object, the greater the intensity of
emitted infrared radiation.
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Source: FLIR Course Manual
15. Hot Steel Glowing Includes
Emitted Energy
Hot steel emitting light or energy in at least the visible
portion of the electromagnetic spectrum. Not all hot
metals glow visually like steel, for example aluminum.
Emitted Energy= K T
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17. Opaque and Transparent
Transmitted light is limited to transparent objects.
The frequency of the electromagnetic energy source
can determine if an object is opaque or transparent.
Opaque Transparent
Absorbed
Absorbed
Reflected Reflected
Transmitted=0
Transmitted=0
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Germanium Glass
Visible Light Visible Light
19. Commonly Used Infrared
Wavelength (Microns)
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Near IR
Long IRMid IR Not
Used
Not
Used
(Used for Thermography)
Source: FLIR Course Manual
20. What is a Blackbody?
A blackbody is a perfect or ideal absorber or emitter
of radiation at a temperature above absolute zero.
In reality, a black body does not exist.
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If λ<d
λ
Cavity with opaque walls
If λ>dBlackbody Radiation
Reflection & Diffraction
Opening (diameter=d)
21. Emissivity (ε)
Emissivity is the ability of an object to emit radiation
and is the ratio of emission from an object as
compared to a black body.
Emissivity of a Blackbody is 1.
Emissivity = ε =
Actual Emission from Object at temperature T
Emission from Blackbody at temperature T
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22. Emissivity of Common
Materials at 300°Kelvin
Aluminum Foil .04
Masonry Plastered 0.93
Nickel 0.03
Paint 0.96
Glass 0.93
Tile 0.97
Copper 0.03
Granite 0.45
Note: Metals have a low emissivity!!
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23. Emitted, Apparent & Reflected
Apparent Temperatures
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Emitted Temperature
Apparent Temperature
Reflected Apparent
Temperature (RAT)
(1-ε)
ε
Target
Camera
Attempt to match the emissivity setting of the camera to the
emissivity of target.
Reflectivity
24. Planck’s Law (1900)
Classical theory called for infinite energy at the higher
frequencies and is referred to as the Ultraviolet
catastrophe
Max Planck determined electromagnetic energy is
emitted in discrete packets of energy proportional to
frequency
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Source: Wikipedia
Depicted curves
presume blackbodies
26. IR Detector Devices
IR detectors consists of generally two types of devices:
Un-cooled – Most common and functions at room
temperature and is generally made using compound
semiconductors (e.g., Lead Selenide & Indium
Antimonide).
Cryogenically cooled - More expensive and more
accurate though more susceptible to damage and
requires cryogenically cooling.
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31. Electrical Tape on Three Metal
Cans
Electrical Tape (.95) has much higher emissivity than
metal (.2) of can.
Visual Infrared
Hot
Can
Can at
Room
Temp.
Cold
Can
Hot
Can
Can at
Room
Temp.
Cold
Can
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Case for Infrared is broader than only Power Quality.Poor electrical connections includes loose neutrals.
Improper torque of componentsMust have current.
Clips can anneal over time increasing the contact resistance, thereby causing hot spotsConnections within molded-case breaker
The chart indicates both the frequency and wavelength. As the frequency increases the wavelength decreases, vice versa.The higher the frequency the greater the energy. For example, the highest frequency energy depicted is gamma rays, which are so energetic there known as ionizing radiation. It is worth noting that the visible spectrum is sandwiched between the UV & IR. On the right we see radio waves. At around 10 to the twelfth hertz or 1 terahertz the characteristics of the energy is finding a number of new uses.
Sir William Herschel
Germanium is an element that is opaque to visible light. However it is transparent to IR.Obviously, glass is transparent to visible light.Another example, clothing is opaque to visible light. However, clothing is transparent to electromagnetic wave called the terahertz waves or T-waves. In the future, terahertz waves will be used in security in place of backscatter x-rays.
A space blanket (also known as a Mylar blanket, first aid blanket, emergency blanket, thermal blanket or weather blanket) is a blanket used in emergencies to reduce heat loss in a person's body caused by thermal radiation, water evaporation and convection.
The above triangle is not an exact mathematical representation. The triangle is only used as an analogy to the power triangle to help viewers having an electrical background generally understand the physics of the IR camera.
The lens is made of germanium, which filters visible light frequencies.
Can be like looking at the world through a pin-hole.Can be expensive and should prioritize use to vital few and trivial many.
Assume balanced loadDiagrams above assume third harmonic is a third the magnitude of the fundamentalCurrents above viewed from line and neutral, respectivelyThe third harmonic line currents are superimposed on top of each other appearing as one current. For this reason, the third harmonics add algebraically having a substantial magnitude.
