Checking Electrical Applications with a Thermal Imager
Thermal imagers can be helpful to check various electrical system components without pausing your process. In fact, your electrical system needs to be running at it’s normal load to accurately check out your potential faults. The load on your electrical systems needs to be running no less than 40% of the maximum load capacity and if you can run your system at full load for the testing, that is an even better approach. This is one of the beauties of thermal imagers, there is no pause in production while you are checking your system!
When testing electrical components, it is important to follow the NFPA 70E standard for Electrical Safety in the Workplace. When performing your thermal testing, it is going to be necessary to wear proper PPE gear. Rubber insulating gloves, ARC flash suits, fire retardant clothing and proper face shields are still a very important part of this testing. It is ideal to try to be no less than four feet away from any open and live panels that you may be observing.
Emissivity is something that will play a huge role in your thermal imaging. Emissivity ratings describe how well and object will be able to correctly display its surface temperature to the thermal imager. The scale for emissivity is from 0.0 – 1.0 and you will receive better readings from the material with a higher emissivity rating. Reflective properties can really lower emissivity and make it hard to get an accurate reading. Higher ratings come from materials that are not reflective and the lower numbers are more reflective. Things such as aluminum, stainless steel, flashing, copper, chrome or nickel are harder to get a true number on. This problem can be somewhat alleviated by waiting to photograph the material in an overcast light or when it is shaded. Painted surfaces usually register from .90-.98 on this scale. Materials such as rubber, ceramics or painted items really make it easier to get a good thermographic reading.
One very common practice with thermographic cameras is taking readings and inspections of breakers and breaker panels. When photographing breakers, you usually want to be looking for a hot spot. If you see a breaker running hot, you will want to pay attention to the wires connected to the breaker. If the heat signal travels up the electrical wire that is feeding into the breaker, you can bet that you have a load problem. If the heat signature is isolated to the breaker itself, you can almost be assured that the breaker is on its last leg or is already gone. Thermographic cameras are definitely they fastest way to get these breaker panels inspected, just don’t forget that it is imperative to photograph the breaker after the repair to ensure that the correct item was fixed and things are now working properly.
Thermal cameras are frequently used in transformer testing as well. Transformers are always around close by to a process environment and in some cases are even right in the plant or facility depending on the amount of power that is used in the facility. Testing the outside of a transformer is relatively simple and can be photographed from the outside or have a picture taken of the inside, depending on the inspection you are performing. When photographing the transformer’s exterior, you can easily see the bushings of the transformer. If the transformer is overheating, you can typically trace this problem to a loose connection or too heavy of a load for the transformer to step the power down. On the inside of the transformer, you can see the coils and the oil. You will want to focus the camera lens onto the coils inside of the transformer. If the coils are hotter than they should be, there is a very good chance that you are leaking or losing oil and the coils cannot properly cool. The oil inside of the transformer functions as a method of cooling the internal coils, if they are running hot then you should inspect the oil level inside the transformer. A faulty transformer is considered an urgently needed repair or replacement.
Thermal imagers are great at finding overloaded circuits as well. The most common fault is an overstressed circuit breaker, these breakers control the flow of electricity. If the breaker overheats then it can no longer carry the load coming into the panel. The conductors in your facility should all have a standard operating temperature and it is very common to find these overheating if they are faulty as well. Most all excess current or wasted current is lost as heat. If you see your utility bill spiking all of a sudden, that is a huge cue to call JM Test Systems and rent a thermal imager to quickly isolate and repair the fault in your process.
Lastly, thermal cameras can be very useful for spotting a three-phase imbalance in a system. If you see a higher temperature in one leg of a three-phase system, you should always follow that circuit to see what may be influencing this problem. When shooting a three-phase system, anything cooler than the other phases is a failed component and anything running hotter means that more load is coming to that one phase. There are lots of different reasons you may be seeing an imbalance in your three-phase system. Harmonics can even play a role in making a three-phase system unbalanced. It is a good idea to use a power analyzer to pinpoint exactly what is going on before making a repair. Another culprit can be voltage drops across fuses. This can be shown as excess heat at the fault; you can then use a clamp on meter or a standard multimeter to pinpoint and verify the exact fuse that would need a replacement.
One of the most common misconceptions when using thermal imagers for electrical testing is that you need to always be looking for something that is hotter than the items that it is working in sync with. That can certainly be true, but it should be just as alarming to the user if they see a component that is showing a much cooler signature than the counterpart. As a general rule, heat does indicate that there is a dysfunctional piece of equipment. Shafts, motors, breakers can all show a hot heat signature if something is faulty. It is just as important to pay attention to things showing cooler than their counterparts as well. If it is cooler it probably just is not working at all and no load is being sent through the equipment. Secondly, it is important to understand that a thermal imager can not see through walls or clothing or any material such as that. It can see the heat that is transferred to the image in front of the lens. You can see pipes behind a wall if the heat or cold is transferred to the wall, but you can not see pipes behind a wall that are not relaying their heat signature to the surface your camera is seeing. When taking pictures of breakers, fuses, shafts, etc. it is imperative to have the camera directly on the item in question. If you are trying to trace piping or maybe find water leaks or something like that, then you are relying on the heat signature that is transferred to the outer material since there is not a way to directly photograph the subject.
JM Test Systems is an authorized distributor for FLIR cameras. We have recently added the FLIR T530 camera to our rental department and it has produced an overwhelming amount of success stories from our clients who have rented them. In addition to rental, JM Test Systems also offers the purchase option on FLIR cameras. The FLIR T530 boasts a 4” LCD, video and photo capabilities, laser assisted focus, a temperature range up to 2192°F with a ±3.6°F accuracy and over 76,000 pixels to make sure that you get the perfect photographs you need! If you would like to see more information or maybe request a quick quote from us, please visit this link or give us a call at 1-800-353-3411.