John H. Waggoner, Senior Instructor at Infrared Training Center, explains why new technology can help pinpoint problems and guides professionals on repairs.
Heat is a byproduct of operating any sized electrical circuit. Most problems in electrical systems display themselves in terms of heat. Electricians must be able to classify a circuit as normal when the load is on or identify when it is abnormal and identify the issues that presents – finding hot spots that need attention. In recent years, new infrared thermography – also called thermal imaging – has come on the market. The non-contact method includes cameras that help electricians and service technicians find and solve problems quicker and more safely. The newest cameras combine both thermal imaging and electrical measurement features in one inspection, troubleshooting, and diagnostic tool that speeds up the process and provides much better information on which to base repair work.
Methods for inspecting and analysing electrical systems
In the past, the only way electricians had to inspect and analyze electrical systems was with hands on testing – usually done after turning off the power to make sure it was electrically safe. Electricians typically go in with testing equipment and tools to connect test leads to determine if there are any issues. Many used contact measurement techniques featuring thermocouples, which produce a temperature-dependent voltage that can be interpreted to measure heat.
With these traditional inspection and maintenance methods, electricians cannot see all the possible issues, but instead must rely on guesswork, checking out connections one by one. This method does not guarantee that heat-related conditions will be solved, because turning off the power removes the load. One can measure if a circuit is overloaded, but when the power is off it is not always possible to know for sure if the problem in the circuit was fixed.
In recent years, electricians also began using spot radiometers: small hand-held non-contact devices that can be pointed at a target to obtain a temperature measurement. Radiometers provide acceptable measurements within certain limits, but no visual imagery is available.
A step up from direct measurement and spot radiometry is thermal imaging, which detects infrared energy emitted from an object, converts it to temperature, and displays an image of temperature distribution, called a thermogram. Since infrared radiation is emitted by all objects with a temperature above absolute zero, thermography makes it possible to see the environment with or without visible illumination.
Thermal imaging provides electricians with a far higher ability to analyze, recommend, and diagnose. With thermal imaging, one can use a camera on a circuit breaker to determine if connections are loose, if there is too great a load on the breaker, and if there are any issues with the breaker contacts. Electricians can find the problem, fix it, then go back with the thermal camera and take an image to verify that the work done has actually solved the problem. In the past, it was very difficult to assure customers that work done had really fixed the problem. Now electricians frequently provide their customers with “before” and “after” imagery.
A wide range of electrical equipment can be inspected with thermal imagers, including transformers, switchgear components, breakers, fused disconnects, non-fused disconnects, conductors, terminations, contactors, control wiring terminations, buss duct (open and enclosed), distribution and branch circuit breaker panels, and motors.
Benefits and advantages of thermal imaging
In effect, thermal imaging allows electricians and electrical technicians to picture heat that the eyes cannot see. This has three main benefits. First, it is a non-contact approach, so electricians do not have to actually touch electrical equipment to determine if the heat is within normal operating temperatures or has moved into abnormal temperatures.
Second, electricians can use thermal cameras as a visual tool to demonstrate to customers the severity of electrical problems. Infrared cameras produce an image of a target that is similar to visual photographs. Many also produce a visual image that can be placed next to the thermal image for a side-by-side comparison. This helps the electrician show customers the exact location and nature of potential faults.
The third benefit is that thermal imaging can be performed in real time. Over the past decade, video-capture technology for infrared cameras has greatly improved. This allows electricians to observe and analyze electrical equipment as it heats up and begins to operate, as it operates under normal conditions over time, and as the target cools down. There is also the ability to watch fast-moving targets, as the recording speed, or frames-per-second (FPS), has improved. Cameras that record at higher frame rates allow the user to observe targets that are changing temperature rapidly, or those that are moving very fast. The equipment now allows us to see that fast transition of temperatures or fast transition of the targets.
Key application areas for thermal imaging
Thermal imaging is used in three general application areas. Utilities rely on it extensively for medium and high voltage equipment (overhead lines and connections), and for substation equipment (breakers, switches, transformers, capacitors, and voltage regulators), to name a few. Thermal imaging is also used for voltages below 1000 Volts, largely for enclosed equipment that supports industrial and commercial operations.
The third category, the newest level of application, is the residential market. Home inspectors and electrical service and HVAC service companies have started to purchase and use thermography for troubleshooting and inspection of residential electrical systems. The growth in this market is due to IR cameras becoming more affordable over the past decade.
Thermal imaging equipment available to electricians
There is a wide range of thermography equipment for electricians, varying from low resolution cameras costing £300 to high resolution cameras costing more than £30,000. The difference among thermal imaging resolutions affects how close one needs to stand to image a target, and the different accessories available for viewing and adjusting the camera and measuring temperature.
At the low end, one can simply select an attachment to a smartphone (both iOS and Android), For example, the FLIR ONE Pro is a device containing an 80 x 60 pixel resolution long wavelength infrared (LWIR) camera.
Higher-end thermal imaging technology, such as the FLIR T1K, can produce up to 1024 x 768 pixel images. Dynamic focus control, continuous autofocus, and a user-friendly interface with an ergonomic design and rotating optical block make it easier to do numerous inspections in one day and to scan at difficult angles.
Another option that has recently come on the market are meters that combine thermal imaging with electrical measurement features in one inspection, troubleshooting, and diagnostic tool. These new meters can take voltage, current, and millivolt drop measurements while also taking an infrared image with the same device. This offers more information for an electrician or technician to make a determination, provides images to confirm the electrician’s diagnosis, and offers proof showing where the problems are. Combining several tools into one reduces the total amount of time it takes to diagnose issues and increases a technician’s speed. It also makes the technician more skillful at troubleshooting, repair, and maintenance work.
One example is the FLIR DM285, which offers 18 measurement functions, including true-RMS (root-mean square), LoZ (low impedance), and non-contact voltage (NCV). This device also includes a thermocouple input and allows users to view thermal and electrical measurements simultaneously. The combined meter uses IGM™ (infrared guided measurement) thermal imaging technology to visually guide users to the precise location of a problem.
Thermal imaging solves real problems
Thermal imaging has been used all over the world to diagnose and solve electrical system problems. The accompanying image shows a large junction box where one conductor was hotter than the eight others. Using the thermal imaging camera, technicians located it not in the box, but 45m back. It would not have been possible to locate this serious issue any other way.
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