This article provides a brief introduction to the key principles of infrared thermography, its main advantages and disadvantages, and how it can be applied to analyze the health of an electrical installation and consequently reduce energy consumption and improve energy efficiency.
The foundation for infrared thermography (also known as thermal imaging), is that all objects emit infrared. A special thermal imaging camera can make visual displays of the amount of infrared energy emitted, transmitted and reflected by an object. In other words, thermal imaging makes the invisible infrared radiation visible.
Its great practical use stems from the fact that the amount of infrared radiation increases with an object’s temperature. The technique can therefore be used to measure the temperature of an object. Moreover, the use of infrared thermography in electrical installations is to see the variations in temperature between various components. Infrared thermography has mainly proved its worth when the temperature difference is significant or when excessive heat is produced (hot spot).
Thermal Imaging Cameras
A thermal imaging camera works by converting infrared energy into a visible light display – a thermogram – which in turn is translated into electrical impulses. These impulses are translated into data for the camera display. This information appears on the display as different colors, depending on the intensity of the infrared emission and therefore of the temperature of the object.
Two main types of camera exist: those with cooled and those with uncooled image detectors. Cooled infrared cameras give a superior image quality, but their purchase price is higher and they are less easy to work with than uncooled cameras.
Most cameras have built-in digital cameras which allow visual and infrared images to be merged. Such a feature is helpful when analyzing images and making reports.
Key considerations when buying a camera include whether the pictures are to be saved and/or shared with others, and whether the actual temperature of the component is needed, or merely temperature differences.
Typical problems in electrical installations that can be detected with infrared thermography include:
- Connections that are loose, poorly installed, corroded etc.
- Unbalanced loads.
- Defective equipment.
- Undersized conductors.
- Overheated motors.
- Overloaded circuits.
- Potential fire hazards.
- Worn components.
- Thermal abnormalities in batteries.
- Harmonic problems.
Advantages and Disadvantages of Infrared Thermography
These are the most important advantages of thermal thermography:
- No need to take the electrical installation out of service since it can be used during normal operating conditions.
- It is a non-contact and a non-destructive test method, used from a safe distance.
- It gives a visual picture of the condition of the installation and its components.
- The results are available in real-time and there is little or no processing needed.
- IR cameras are relatively easy to use.
- It can detect conditions and defects before they become serious problems.
- Large electrical cabinets and whole electrical installations can be quickly scanned.
- The exact location of the potential problematic point can be easily determined.
The technique does have certain drawbacks. To interpret the results requires a certain experience and knowledge. Obtaining high accuracy can be difficult due to varying emissivity of the different materials; reflections from other surfaces; and other characteristics. And as it is necessary to have a direct view of the electrical components being scanned, covers have to be removed, which can be a hazardous activity.
Infrared Thermography and Energy Efficiency
The problems noted in section 2.3 result in increased electrical resistance and therefore the production of excessive heat. This excessive heat increases the fire risk, reduces reliability, and is a pure waste of energy.
Through infrared thermographic inspections, these unwanted hot spots can be detected, to identify sources of energy loss in electrical installations and electrical equipment.
Qualified thermographers will be able to draw conclusions from the thermal data acquired during the scanning, taking into account the current load, the ambient temperature, and other local conditions. Based on their knowledge of the camera used and of the electrical installation scanned, they can suggest follow-up actions such as maintenance, repair or replacement of the troublesome component or equipment. Shutdowns due to equipment failure can thus be avoided, the installation will be safer because the fire risk is diminished, and energy will be saved through eliminating unnecessary heat loss.