Detecting Electrical System Overloads
Tip written by: Infraspection Institute
Statistically, overloaded circuits are the second most common cause of exceptions found during infrared inspections of electrical systems. Although overloads are quite common, they can be tricky to accurately diagnose.
As electrical current flows through a conductor, heat is generated. As circuit load increases, so does the amount of heat. Electrical circuits are designed so that loads will not exceed the circuit’s ability to safely carry a sustained load and the amount of heat associated with such load.
Typically, overcurrent protection devices such as fuses or circuit breakers are designed to protect circuits from overload conditions. These devices will interrupt the circuit when the current reaches a predetermined level for a specified period of time.
Serious problems such as fires can be caused by sustained overloads. Such overloads may be caused by: improperly sized wiring, and improperly sized or defective overcurrent protection. Fortunately, a thermal imager can be used to detect the thermal patterns associated with sustained overloads.
When using a thermal imager to detect potential overloads, one should keep the following in mind:
- Overloaded conductor(s) will be uniformly warm throughout entire length
- For polyphase circuits, all conductors may be uniformly warm
- Depending upon ambient conditions and imager settings, overloaded circuits may not appear remarkably warmer than adjacent circuits
Because an infrared imager cannot measure electrical current, suspected overloads must be confirmed with an ammeter while observing all requisite safety precautions. For greatest accuracy, a true RMS sensing ammeter is recommended. Circuits found to be overloaded should be immediately investigated for cause and corrected.
Infrared inspection of power distribution systems is one of the many topics covered in the Level I Infraspection Institute Certified Infrared Thermographer® training course. For information on thermographer training or to obtain a copy of the Standard for Infrared Inspection of Electrical Systems & Rotating Equipment, visit us online at www.infraspection.com or call us at 609-239-4788.
It’s Not That Easy
Ever wonder why magicians never reveal their secrets? It’s because magic, like most things, is easy once you know the trick. When describing thermography in lay terms, it is easy to over emphasize simplicity and forget the source of the true magic behind thermography – the thermographer.
An infrared inspection system consists of infrared imaging equipment, a thermographer, and the knowledge that he/she possesses. Of these three things, the greatest limiting factor in an infrared inspection is the thermographer.
In order to be an effective thermographer, one must be trained in the following:
- Theory and construction of the object or system being inspected
- Infrared theory and heat transfer principles
- Use and operation of infrared imaging equipment
- Non-contact temperature measurement error sources and how to avoid or correct for them
- Site-specific safety requirements and the use of appropriate PPE
In addition to the above, qualified thermographers must also be experienced with inspecting the subject system. When all things are considered, effective thermographers need considerable training and field experience. Making thermography look simple is a true testament to the skills of a professional thermographer.
The next time you hear the dismissive claim that thermography is easy, remember, it is only easy after someone has invested considerable time and effort to learn the art and science of the trade. In a magic show, the magic comes from the magician, not the wand. In thermography, the magic comes from the thermographer.
Visit Infraspection Institute online or call us at 609-239-4788.
Infrared Inspections of Retrofitted Roofs
If your roof has been retrofitted with a new roof installed over an existing one, it is imperative that you test the roofing system for water infiltration at least annually. With limited opportunity for egress, water entering the upper roof of a retrofitted system can cause widespread damage in a very short period of time. To make matters worse, there is usually no visual evidence of this type of a leak from inside of the building.
Performed in conjunction with regular visual inspections of your roof, infrared inspections of low slope roofs are a very cost effective way of tracking the overall health of your facility’s roofing system. Locating leaking areas while they are small allows them to be addressed before they can spread. Additionally, moisture trapped within a roofing system almost never dries out and can cause premature failure of the roofing membrane, adhesives, fasteners, and the roof deck.
Whether you choose to have an in-house thermography team or an outside contractor perform the inspection, make certain that the Thermographer is both Certified and experienced. Since an infrared imager cannot confirm moisture presence, all infrared data must be verified by invasive testing as well.
Infrared inspection of flat roofs is one of the many topics covered in the Infraspection Institute Level I Certified Infrared Thermographer® training course. For more information or to register for a course, visit Infraspection Institute or call us at 609-239-4788.