786                                         PIERS Proceedings, Marrakesh, MOROCCO, March 20–23, 2011Infrared Thermography ...
Progress In Electromagnetics Research Symposium Proceedings, Marrakesh, Morocco, Mar. 20–23, 2011 787the thermographic ins...
788                                     PIERS Proceedings, Marrakesh, MOROCCO, March 20–23, 2011                          ...
Progress In Electromagnetics Research Symposium Proceedings, Marrakesh, Morocco, Mar. 20–23, 2011 789                    T...
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  1. 1. 786 PIERS Proceedings, Marrakesh, MOROCCO, March 20–23, 2011Infrared Thermography for Assessing and Monitoring Electrical Components within Concrete Structures Mohd Shawal Jadin1 , Soib Taib1 , and Shahid Kabir2 1 School of Electrical and Electronic Engineering, Universiti Sains Malaysia Nibong Tebal 14300, P. Pinang, Malaysia 2 Collaborative Micro-electronic Design Excellence Centre (CEDEC) Universiti Sains Malaysia, Nibong Tebal 14300, P. Pinang, Malaysia Abstract— The paper presents the application of infrared thermography (IRT) for assessing and monitoring electrical components within concrete structures. It is well known that the in- tegrity of a power system is of paramount importance when it supplies electricity throughout a facility, especially during peak time. Overloading, load imbalance, corrosion and loose connection of electrical components can produce a thermal anomaly or hot spot. The abnormality of the components will occur when its internal temperature reached beyond its limits. Consequently, the overheating of the electrical component within the concrete structure can potentially result in unplanned power outages, possible injury and fire hazard. In addition, the efficiency of an electrical system becomes low prior to failure, thus energy is spent generating heat in the struc- ture, causing unnecessary loses. Therefore, early prevention is required to avoid future faults and increase the reliability of the electrical components. Conventionally, for a large building and wide area of power distribution systems, the inspection of electrical power components within the structure requires extra manpower to conduct the test and take a lot of time as well as cost. Furthermore, only certified and experienced personnel can justify the severity of the problematic components. This is due to the complex analysis and various factors should be considered during the inspection especially when the cables are deep into the structure. Therefore, this research proposed a new method of an intelligent monitoring system for electrical components by diag- nosing its thermal profiles. The system uses infrared thermographic camera or thermal imager in order to capture the thermal behavior of electrical components in the concrete structure. The main feature of the proposed system is to automatically identify the thermal anomaly in elec- trical components and classify its level of severity if the anomaly is detected. A new method of inspection is introduced by implementing the combination of an advanced image processing technique and artificial intelligence system. Finally, the system will give a complete analysis report, including the most suitable action to be taken for the problem that was detected.1. INTRODUCTIONIn 1800, William Hershel has discovered infrared radiation and it was the first experiment thatshowed there were forms of light not visible to the human eye [1, 2]. The infrared wavelengthspectrum is ranged from about 1 mm down to 750 nm. All objects emit energy proportional to itssurface temperature. As infrared energy functions outside the dynamic range of the human eye,special equipment is required to transform the infrared energy to another signal, which can be seenby human eye. For this purpose, infrared imagers were developed to see and measure this heat.Nowadays, various types of IRT imager with more advanced and sophisticated features have beendeveloped [3]. The basic concepts of IRT imager or well known as thermographic camera is that itcan captures the image of the thermal pattern and measures the emissive power of a surface in anarea at various temperature ranges. The digital image of IRT is called as thermograms. Each pixelof a thermogram has the specific temperature value, and the image’s contrast is derived from thedifferences in surface temperature. Temperature and the resulting thermal behavior of electrical components are the most criticalfactors in the reliability of any operation or facility [4]. The abnormality of the components willoccur when its internal temperature reached beyond its limits. Electrical components such asburied electrical cable and wiring within a concrete wall and structure can produce overheatingwhilst under load. This will result a high surface temperature over a buried electrical supply andcan, of course, indicate a potential of fire risk [5]. In addition, the efficiency of an electrical supplybecomes low prior to failure, thus energy is spent generating heat, causing unnecessary loses. IRT camera can detect the abnormality of power components without interrupting the powersystem operation. However, most of the inspection can only be done by well-qualified and ex-perienced personnel. Otherwise, the inspection will result a wrong interpretation. Commonly,
  2. 2. Progress In Electromagnetics Research Symposium Proceedings, Marrakesh, Morocco, Mar. 20–23, 2011 787the thermographic inspection of electrical components will take a lot of time and high inspectioncost [6]. Therefore, applying an automatic analyzing system can overcome this situation. Thethermal abnormality of electrical components can be detected with quickly and accurately even theexpert or experienced personnel are not present. This paper proposed an automatic IRT diagnosissystem for monitoring the reliability of electrical power components.2. TYPICAL FAULTS IN ELECTRICAL COMPONENTSAll electrical devices are usually rated for power, which indicates the amount of energy that thedevices can conduct without being damaged. If the device is operated at a power above its specifica-tions, the excess power can reduce the device’s life cycle and efficiency. Basically, faults in electricalpower system can be classified into few categories, i.e., poor connection, short circuit, overloading,load imbalance and improper component installation [3, 7–11]. In most cases, the major cause ofoverheating in utility components is the change in resistance due to loose connection [12]. Theloose connection causes electricity to use smaller area of the defective connection than required forproper current flow and therefore, increases the resistance and temperature of the connection. Anyproblem, which accompanies a change in resistance of the equipment, causes it to consume morepower than the intended load. According to a thermographic survey conducted during the period of 1999–2005 [13], it was foundthat 48% of the problems were found in conductor connection accessories and bolted connections.This is mainly resulted from the loose connection, corrosion, rust and non-adequate use of inhibitorygrease. On the other hand, 45% of the thermal anomalies appear in disconnectors contacts. Mostof the anomalies are due to deformations, deficient pressure of contact, incorrect alignment of armsand dirtiness. Only 7% of the problems were found in electrical equipments. Another major cause of overheating in electrical components within the structure is overloading.Through IRT camera, the sign of overloading can be seen clearly even if the cable was located deepinto the concrete where the red region which has high temperature value covered all parts of thecomponents or cables. Fig. 1 shows an example of overheating due to overloading in an electricalcable within a concrete wall. By utilizing IRT technology, the thermal image will clearly indicatesthe problematic area. The suspected area can be easily indentified and interpreted. Nevertheless,in some cases, the interpretation of thermographic image cannot be done directly except for anexperienced and qualified thermographers. There are some thermographic characteristic should beunderstood.3. SYSTEM DEVELOPMENTConventional inspection of electrical power components requires a large amount of workers as wellas time and cost. In this exercise only certified and experienced personnel can justify the levelof severity of the suspected components. This is due to the complex analysis and various factorsshould be considered during the inspection. Therefore, this research proposed a new method ofintelligent monitoring system for electrical power equipments by diagnosing its thermal profiles.3.1. System ConfigurationThe main feature of the proposed system is to automatically detect the thermal hot spots andpotential fault location within the concrete structure. The development of monitoring system is toanalyze the running state of electrical components using the combination of artificial intelligenceand advanced image-processing technique. The general block diagram of the proposed system isshown in Fig. 2. Figure 1: IRT image of cable fault in concrete wall.
  3. 3. 788 PIERS Proceedings, Marrakesh, MOROCCO, March 20–23, 2011 Figure 2: General block diagram. Figure 3: General structure of the analyzing process. The image of the electrical components within the concrete structure is captured and thensends to the monitoring system for further analysis. It is a very challenging task in recognizing theelectrical equipments from the complex background in order to judge whether troubles has happenedor potential troubles would happen and finding position of suspected equipments. Therefore, animage processing technique must be applied to filtering and enhancing the captured image. Theoverall process of the system includes several steps: images’ preprocessing, feature extraction, typerecognition, state analysis and classification. After capturing the IRT images, the computer mustpreprocess the images in order to improve images quality, including images’ smoothing, eliminatingnoise, filtering, enhancing edges, etc. the next step is finding the interest region by segmenting theimages. The segmentation process will highlight the hot spot in the suspected component. Theimage features then become the inputs of neural network that has been trained.3.2. Faults ClassificationAnalysis of thermal signatures and the relation to various operating parameters must be accom-plished. The task of determining fault modes is essentially a pattern recognition problem that isan ideal application for a neural network. For this reasons, multilayer perceptron (MLP) neuralnetwork (NN) will be implemented to achieve this. The general structure of the analyzing processis shown in the Fig. 3. The difficulty of the research is to get the accurate reading of the actualtemperature of the electrical power equipments. This is due to various factors that will affect themeasurements. The factors can be classified into two categories, i.e., internal factors and externalsfactors. Internal factors are related to the target components such as the component’s emissivityand thermal gradient. External factor is about the environmental factors such as wind speed, pre-cipitation, solar radiation and ambient temperature. Prior to analysis, all the related data must becollected as the input variables. Therefore, a set of sensors for data acquisition is required. The output will be justified according to qualitative and quantitative analysis. By combiningthese two methods, it is expected to increase the accuracy of inspection. The level of severityof the suspected electrical equipments in the concrete structure can be classified according tostandards [14] as shown in Table 1. The recommended action should be taken according to thelevel of priority. The final process of the inspection is preparing the analysis report. Analysisreport will contain all the required information for the future analysis and maintenance. This willinclude the location, date, specific problem, corrective action, infrared image and visible light image.Additional specific information related to equipment’s temperature vs. acceptance criteria, ambienttemperature conditions, equipment’s load (for electrical equipment), and type of IRT camera areuseful for subsequent data analysis and future inspection.
  4. 4. Progress In Electromagnetics Research Symposium Proceedings, Marrakesh, Morocco, Mar. 20–23, 2011 789 Table 1: Classification of thermal profile of electrical components. Priority ∆T (◦ C)-similar components ∆T (◦ C) over ambient Recommended Action 4 1–3 1–10 Minor problem 3 4–15 11–20 Repair as time permits 2 --- 21–40 Serious problem 1 > 15 > 40 Critical, Repair immediately4. CONCLUSIONIt is clearly shown that early prevention is required to avoid future faults and increase the reliabilityof the electrical power components within concrete structure. Since the electricity demand hasincreased day by day, IRT inspection should be done regularly especially in building where most ofthe electrical cable or components are within the concrete structure. By implementing an automaticdiagnosis system, it can provide faster and more accurate IRT analysis for hazard protection. Theclassification procedure is a useful tool and plays an important role in predictive and preventivemaintenance program.ACKNOWLEDGMENTThis research was supported by Fundamental Research Grant Scheme (FRGS), Universiti SainsMalaysia and Universiti Malaysia Pahang.REFERENCES 1. Lizak, F. and M. Kolcun, “Improving reliability and decreasing losses of electrical system with infrared thermography,” Acta Electrotechnica et Informatica, Vol. 8, No. 1, 60–63, 2008. 2. Chou, Y. and L. Yao, “Automatic diagnostic system of electrical equipment using infrared thermography,” Proceedings of International Conference of Soft Computing and Pattern Recog- nition, 155–160, 2009. 3. Braunovic, M., N. K. Myshkin, and V. V. Konchits, Electrical Contacts Fundamentals, Appli- cations and Technology, CRC Press, 2007. 4. Chuck, H., Handbook of Nondestructive Evaluation, 1st Edition, McGraw-Hill Professional, 2001. 5. Epperly, R., G. Heberlein, and L. Ead, “A tool for reliability and safety: Predict and pre- vent equipment failures with thermography,” Proceedings of Petroleum and Chemical Industry Conference, 59–68, 1997. 6. Cao, Y., X.-M. Gu, and Q. Jin, “Infrared technology in the fault diagnosis of substation equipment,” Proceedings of International Conference on Electricity Distribution, China, 2008. 7. Balaras, C. A. and A. A. Argiriou, “Infrared thermography for building diagnostics,” Energy and Buildings, Vol. 34, 171–183, 2002. 8. Dos Santos, L., E. C. Bortoni, L. E. Souza, G. S. Bastos, and M. A. C. Craveiro, “Infrared thermography applied for outdoor power substations,” Proceedings of SPIE, 69390R-69390R- 11, 2008. 9. Hou, N., “The infrared thermography diagnostic technique of high-voltage electrical equip- ments with internal faults,” Proceedings of International Conference on Power System Tech- nology, 110–115, Beijing, China, 1998.10. Kregg, M. A., “Benefits of using infrared thermography in utility substations,” Proceedings of SPIE, 249–257, 2004.11. Azmat, Z. and D. Turner, “Infrared thermography and its role in rural utility environment,” Proceedings of Rural Electric Power Conference, B2/1–B2/4, 2005.12. Mart´ ınez, J. and R. Lagioia, “Experience performing infrared thermography in the maintenance of a distribution utility,” Proceedings of International Conference on Electricity Distribution, Vienna, 2007.13. Titman, D. J., “Applications of thermography in non-destructive testing of structures,” NDT & E International, Vol. 34, No. 2, 149–154, 2001.14. “Standard for infrared inspection of electrical systems & rotating equipment,” Infraspection Institute, 2008.