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IR Facts
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Infrared Inspections on Electric Panels without Removing Covers: Can the Inspection be Completed Correctly?
Joe Gierlach Director Technical Training and Support TEGG Corporation
Joe DeMonte Senior Thermography Course Instructor
There has existed in the past a misunderstanding that Infrared Thermography could be accomplished without the benefit of removing panel and/or dead front covers on electrical apparatus.
EXAMPLES TAKEN DURING INFRARED INSPECTIONS
The following examples were taken on site during actual component inspections over the last year. Provided are details of each component shown both with infrared images prior to removing the cover and after removing the cover.
Our first two examples explore the possibility of doing proper IR thermography in breaker panels without removing the dead front cover to view the actual buss and load side lugs.
EXAMPLE #1
As you can see in figure #1 prior to the removal of the dead front cover, there is an obvious load on the suspect breaker 4th down on the right.
FIGURE #1
The observed temperature is around 30 degrees C and within manufacturer operating specifications. The temperature on the dead front cover is closer to 23 degrees C and not an apparent concern, right? One may simply deduce this is only load created energy on the breaker and bypass it during an inspection.
Once the cover is removed, a far worse issue is revealed in Figure #2
FIGURE #2
- The problem area centered on the line side connection.
- The actual problem temperature at this light load was approximately 39 degrees C
- This is an error or nearly 9 degrees C
- Absent removal of the cover, this more than likely would have been bypassed
- Any addition of loads would increase the problem temperature exponentially
EXAMPLE #2
FIGURE #3
- Again a lightly loaded breaker compared to the rating
- Around 32 Degrees C on the breaker case and well within Manufacturer Specifications for rise over ambient
- No apparent “deficiency” observed related to temperature on the dead front cover and operating around 22 degrees C by viewing the thermal image in figure #3
- But when the cover is removed, a different story is uncovered as is shown in figure #4…..
- As seen below in Figure #4, the actual problem area again is the bus connection to the breaker
- But unlike the 22 degree C observed on the dead front cover, the problem temperature is now running closer to 43 degrees C
- This is an error of nearly 22 degrees C
FIGURE #4
Again with load demand being light at the time of the survey, increases must be considered and the consequences thereof. This is another clear example of how temperature errors by improper procedure of the technology for the electrical application can occur.
The next part of this discussion will be used to determine whether or not cabinet doors themselves need to be removed to perform a satisfactory infrared survey.
EXAMPLE #3
Our next example is of a 480V main disconnect on the outside of a customer’s business. Figure #9 shows both the visible and IR images of the cabinet.
No issues were noted from the outside inspection. We then opened the cabinet using approved safety procedures and scanned the internal fused disconnect to look for suspicious hot spots. The problem would have been missed! Refer to Figure #10 for an infrared image clearly showing a problem on the C phase incoming connection. We needed to open this cover in order to identify it. The C-phase fuse was in need of replacement, so the recommended action was to replace all three with new fuses.
FIGURE #9: 480V Main Disconnect
FIGURE #10: 480V Fused Disconnect
Our last example in this paper is a medium voltage breaker with the dead front cover still in place. We have a minor temperature rise of about 3°C shown on breaker #4 (see figure #11).
FIGURE #11: 480V Breaker #4
This infrared image shows that the breaker is a little warm, but not warm enough to warrant further investigation, right? We pulled the dead front cover, again following all safety regs, to see if there was anything worth reporting to our important customer.
FIGURE #12: 480V Breaker #4 with Load Side Cover Removed
This image (figure #12) shows that the contact temperature was about 10°C higher than what was shown on the surface of the breaker. Also, NO anomaly was shown on the outside of the cover itself. We decided to remove the buss side cover to investigate the other side.
FIGURE #13: 480V Breaker with Buss and Load Side Cover Removed
With the load side cover removed (figure #13), we noted a slight rise on the middle phase connection. The “issue” on the bottom phase buss was a reflection, but the connection was a true hot spot. It was at this point that we used our other tools available to get a voltage drop across the different connections and breaker contacts to determine where our issue was emanating from. With over a .275-millivolt drop across the B-phase contact of the breaker itself, we determined that breaker #4 was in need of replacement.
In one final example at a Medical Treatment Center in Fairbanks, Alaska, a Square D I-Line Panel rated at 800 amps was our target. Prior to performing any maintenance on the equipment the customary Ultrasonic Airborne Safety Scan was performed and no anomalies were detected. As an additive safety precaution, we also conducted a brief IR scan with the camera on the exterior of the panel. The Digital and Infrared images are illustrated below in Figure #14:
FIGURE #14
As indicated in the images, there is no alarming thermal patterns n either the dead front cover (around 30 Degrees C) or main lug access cover. Some indications at the top corner of the dead front do illustrated some energy, but this could be merely load related heating effects. Once the dead front cover is removed, it is a bit more apparent that there is some type of heating occurring near the top of the panel and indicated in Figure #15 below:
FIGURE #15
The image above certainly illustrates that there is something suspect within the panel (Now the temperature is around 42 Degrees C); however, it is still not conclusive as to the source or the severity of the condition contributing to the thermal emission we are observing. Once the top main lug access cover is removed for inspection, it becomes reasonably clear that there is a deficiency on the main lug connections illustrated in Figure #16, but where and which one(s)?
FIGURE #16
Even without the implementation of complete analysis procedures, it is evident that the problem is centered on the main lug assemble and the problem temperature is actually 53 Degrees C. This is nearly a 22 Degree C error in temperature with the covers on and with them removed. Additionally, terminations are rated at 65 Degrees C absolute and this 800 Amp panel had balanced loads of 450-460 amps, only 50% of its rated capacity, and not all of the customers loads were in use at the time of the visit. Once these additional loads are added, the problem temperature will then begin to increase exponentially and it won’t be long before it will exceed the 65 Degree C rating of the lugs and cause them to rapidly deteriorate and ultimately fail, possibly causing a fire and damage to other components.
Once this evidence was presented to the customer immediately while on site, authorization to perform the repairs was secured for 12:00 AM that evening. The panel was deenergized, the main lugs were disassembled, inspected, cleaned with emery cloth, new hardware was used to reinstall it, the toggle bolt was torques to Square D’s specifications, and the panel was returned to service.
At this point the job is completed right? Wrong! We must ALWAYS return to verify any repairs we perform, particularly on agreements where they are guaranteed, using the IR camera to provide an illustration of how effective repairs were. In this case, you can see below in Figure #17, they were extremely successful when returned to service and under the same operating conditions, the “problem” temperature was reduced by nearly 25 Degrees C and well within acceptable operating parameters.
FIGURE #17
SUMMARY
In today’s world, the mentality and “buzzword” is lean manufacturing and reduced maintenance costs. Competition throughout industry demands that we must all do more with fewer resources. This should not mean that in the interest of cost savings shortcuts be taken that can cause misjudgments that may contribute to downtime or equipment failure.
In the examples above, there are no doubt problems that existed on line side connections. Analysis, including voltage drop measurements, confirmed that due to resistance issues thermal energy was being created and radiated. Although there was conduction noted on the breaker cases, it most likely would not be considered to be abnormal, deficient, or in failure stage.
The Square D I-Line panel is an excellent illustration of the types of critical temperature errors that may be realized while performing services if we do not safely take that necessary step of removing ALL covers to have the line of sight to the target. For one to identify and quantify an anomaly on the exterior of an electrical enclosure, the severity of the problem and the amount of thermal radiation needed internally to be visible to the camera would be exponentially higher and near catastrophic failure. In this case, one would not want to attempt to open the enclosure while it was energized and a shutdown would be the prudent course of action to correct the deficiency.
To be accurate in our analysis and identification of anomalies directly relates to our credibility with our customers. For this to be accomplished, we must follow established procedures each and every time we apply the technology. This becomes a function of the application and discipline we are practicing in along with the fundamental knowledge of the equipment we are performing services on.
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