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Infrared Thermography: Power Quality Among Other Things
- 1. May 30 ,2013 Presenter: Gary Malhoit, P.E. 1
- 2. Agenda Why Infrared? Infrared Basics Power Quality, Heat & Reliability Questions & Comments: All 2
- 3. Heraclitus (535-475 BC) 3 “Noman ever steps in the same river twice."
- 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. 4
- 5. Case for UsingInfrared 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) 5
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- 7. Inductive Logic andRisks 7
- 8. Poor Connections &Heat 8 Non- Conducting Hot Conducting Cross-Section (A) Conductor Cross-Sections Hotter Hot Conducting Cross-Section (A) Non- Conducting
- 9. Heat & DiminishingReliability 9 FailureRate Time Infant Mortality Normal Life Wear Out Heat Bathtub curve derived from three Weibull Distributions
- 10. Some Types ofConnections 10 Bolted Connections Clip Connections Crimp & Bolted Connections
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- 12. Heat Transfer Conduction Convection Radiation 12 Source: Earthforce.com
- 13. Electromagnetic Spectrum Lightcomprises only a small portion of the entire electromagnetic spectrum. Most of the electromagnetic spectrum is invisible to the human eye. 13
- 14. Above Absolute Zero All objects emit infrared above absolute zero The warmer the object, the greater the intensity of emitted infrared radiation. 14 Source: FLIR Course Manual
- 15. Hot Steel GlowingIncludes 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 4 15
- 16. Herschel’s Experiment (1800) 16 Blue:80 degrees Yellow: 83 degrees Infrared: 86 degrees Source: FLIR Course Manual
- 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 17 Germanium Glass Visible Light Visible Light
- 18. 18 Opaque Transparent Opaque andTransparent (cont.) Source: FLIR Course Manual
- 19. Commonly Used Infrared Wavelength(Microns) 19 Near IR Long IRMid IR Not Used Not Used (Used for Thermography) Source: FLIR Course Manual
- 20. What is aBlackbody? 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. 20 If λ<d λ Cavity with opaque walls If λ>dBlackbody Radiation Reflection & Diffraction Opening (diameter=d)
- 21. Emissivity (ε) Emissivityis 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 21
- 22. Emissivity of Common Materialsat 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!! 22
- 23. Emitted, Apparent &Reflected Apparent Temperatures 23 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 24 Source: Wikipedia Depicted curves presume blackbodies
- 25. Camera Schematic 25 Processor Target FilterSensor Infrared Visible ε, RAT TApparent Te
- 26. IR Detector Devices IRdetectors 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. 26
- 27. Grayscale Palette Watertown, MA April19, 2013 27
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- 31. Electrical Tape onThree 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 31
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- 37. Harmonics & Heat (SkinEffect) 37 DC: No Skin Effect 60 Hz: Skin Effect 1 KHz: Substantial Skin Effect Region of most current flow =δSkin Depth δ
- 38. Third Harmonics (cont.) 38 Couldbe unbalanced Situation?
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- 40. Heat Pattern Dissipatesfrom Lose Connection 40
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- 42. 42 Strap Between Sectionof ISO Phase Bus
- 43. Infrared Applications 43Source: WallStreet Journal
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Editor's Notes
- #6 Case for Infrared is broader than only Power Quality.Poor electrical connections includes loose neutrals.
- #9 Improper torque of componentsMust have current.
- #11 Clips can anneal over time increasing the contact resistance, thereby causing hot spotsConnections within molded-case breaker
- #14 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.
- #17 Sir William Herschel
- #18 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.
- #23 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.
- #24 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.
- #26 The lens is made of germanium, which filters visible light frequencies.
- #31 Can be like looking at the world through a pin-hole.Can be expensive and should prioritize use to vital few and trivial many.
- #37 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.