By John H. Waggoner
By John H. Waggoner
June 20, 2018 — Heat is a byproduct of operating any-sized electrical circuit, and many problems in electrical systems display themselves in terms of heat. Electricians must be able to classify a loaded circuit as either Normal or Abnormal; if the latter, they should be able to identify the issues that present, i.e. hot spots that need attention.
In recent years, infrared thermography (a.k.a. thermal imaging) cameras have come a long way toward helping electricians and service technicians find and solve problems quicker and more safely. The newest IR cameras combine both thermal imaging and electrical measurement features in one inspection, troubleshooting and diagnostic tool, which speeds up the process and provides better information on which to base repair work.
Methods for inspecting and analyzing electrical systems
In the past, the only way electricians could inspect and analyze electrical systems was with hands-on testing, usually performed after turning the power off to ensure it was electrically safe. Electricians typically go in with testing equipment and tools to connect test leads to determine whether 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, the electrician cannot see all the possible issues, but must instead rely upon educated guesswork, checking connections one by one. This method does not guarantee that heat-related conditions will be solved, because turning the power off also removes the load. One can measure whether a circuit is overloaded, but it is not always possible to know for certain whether the problem in the circuit was fixed when the power is off.
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, diagnose and recommend. With thermal imaging, one can use a camera on a circuit breaker to determine whether connections are loose, there is too great a load on the breaker, or spot any issues with breaker contacts. Electricians can find the problem and fix it, then go back with the thermal camera and take an image to verify the work performed actually solved the problem.
In the past, it was very difficult to assure customers that work done had truly fixed the problem. Now electricians frequently provide their customers with Before and After images.
A range of electrical equipment can be inspected with thermal imagers, including transformers, switchgear components, breakers, fused and non-fused disconnects, conductors, terminations, contactors, control wiring terminations, bus duct (open and enclosed), distribution and branch circuit breaker panels, and motors.
Advantages in thermal imaging
In effect, thermal imaging allows electrical professionals to visualize heat our eyes cannot see, which has three main benefits. First, it is a non-contact approach, so electricians do not have to actually touch electrical equipment to determine whether 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. IR 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 technicians show customers the exact location and nature of potential faults.
The third benefit is thermal imaging can be performed in real time. Over the past decade, video-capture technology for IR cameras has improved greatly. 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 (frames-per-second, FPS) has improved. Cameras that record at higher frame rates allow the user to observe targets that either change temperature rapidly or are moving very fast.
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) inspection, and substation equipment (breakers, switches, transformers, capacitors and voltage regulators), to name a few.
Thermal imaging is also used for voltages below 1000, largely for enclosed equipment that supports industrial and commercial operations.
The third category and newest level of application is the residential market. Home inspectors and electrical and HVAC service companies have started purchasing and using thermography for troubleshooting and inspection of homeowners’ 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
A wide range of thermography equipment is available for electricians, varying from low-resolution cameras costing $400 to high-resolution units costing more than $40,000. 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.
One option that has recently come on the market are meters combining 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 taking an infrared image with the same device.
Thermal imaging is being used all over the world to diagnose and solve electrical system problems, and the technology continues to sport cutting-edge features and increasingly affordable price points. Electricians benefit greatly by being able to see heat with thermal imaging equipment, as it enables them to both pinpoint and diagnose/solve problems faster.
John H. Waggoner is a senior instructor with the Infrared Training Center.
This article originally appeared in the May 2018 issue of Electrical Business Magazine.