-back to applications home- Infrared thermography began its commercial industrial history as a predictive maintenance tool in the mid 1960's in Sweden. The Swedish Power Board used this technology to identify "hot spots" in their substations. The principle behind this application is based on the first law of Thermodynamics. Energy cannot be created or destroyed; it can only be changed from one form to another. In general, the power an electrical system "uses" is defined by the current squared times resistance (P=I2 R). The first law of thermodynamics tells us that the power cannot really disappear; it will simply be transformed into another form of energy. In the case of a poor connection or other high resistance problem, the electrical energy is transformed into thermal energy, which increases the temperature at the point of higher resistance. There are a number of different ways to test this increase in resistance in an electrical system, many of which require contact with the system itself. Infrared thermography, on the other hand, locates the area of high resistance remotely by identifying areas of higher temperature. In other words, thermography is a non-contact measurement tool. As the resistance goes up, the severity of the problem increases, as does the need for attention. With no intervention, the component will reach a state of catastrophic failure, which can result in an electrical fire or a total shutdown of the system involved. This is a very costly and often dangerous situation in any industry. Infrared inspections offer the solution to this problem by identifying electrical anomalies in an accurate, efficient, and safe fashion. The severity of the problem and the repair priority can be determined by categorizing the temperature rise of the fault as compared to a properly operating component under the same loading conditions. Many components in an electrical system are service-rated by temperature. An example is that of THHN wire which is a conductor that is in wide use in many industries. The maximum allowable safe operating temperature of this component is 90 °C. Infrared instruments have the capability of accurately calculating the temperature of components such as this with a high degree of accuracy when an inspection is performed by a properly trained, qualified thermographer.