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Abstrak :
Salah satu cara menjaga performa transformator yaitu dilakukan pemantauan pada isolasi dari transformator tersebut. Sebuah penelitian dari EA Technology menunjukan bahwa 85% terjadinya kegagalan isolasi berhubungan dengan peluahan sebagian. Penelitian ini dilakukan untuk menganalisis parameter-parameter yang berpengaruh terhadap terjadinya peluahan sebagian. Parameter tersebut seperti pembebanan transformator, temperatur transformator, serta umur dari transformator tersebut. Pendeteksian ini dilakukan dengan menggunakan UltraTEV Plus2, yaitu alat untuk mendeteksi adanya aktivitas peluahan sebagian dengan menggunakan metode sensor ultrasonik yang dapat membedakan derau (noise) dan peluahan sebagian. Pengukuran dilakukan pada 34 buah transformator distribusi dengan 20 transformator dikategorikan terdapat aktivitas peluahan sebagian dan 14 transformator lainnya dikategorikan normal. Hasil data pembebanan yang telah dilakukan dihasilkan persentase pembebanan sebesar 10.32% hingga 97.7%. Sedangkan hasil pengukuran temperatur dihasilkan sebesar 27.2°C hingga 103.5°C dengan umur transformator yang bervariasi dari 5 hingga 20 tahun. Hasil pengukuran aktivitas peluahan sebagian dapat digunakan sebagai acuan untuk menilai performa transformator. ......One way to maintain the performance of the distribution transformer is to monitor the insulation of the transformer. A study from EA Technology shows that 85% of insulation failures are associated with partial discharge. This research was conducted to analyze the parameters that influence the occurrence of partial discharge. These parameters are transformer loading, transformer temperature, and age of the transformer. This detection was carried out by using UltraTEV Plus2, a tool for detecting partial discharge activities using the ultrasonic sensor method that can distinguish noise and partial discharge. The measurements were made on 34 distribution transformers with 20 transformers were categorized as having as partial discharge activities and 14 other transformers were categorized as normal. The loading data that have been carried out resulted in a loading percentage of 1.3175% to 74%. While the results of measurements of the temperature were 27.2°C to 93.5°C with the age of the transformer varying from 5-20 years. The results of partial discharge activity measurements can be used as a reference to assess the performance of the transformer.

Abstrak :
Acoustic emission (AE) technique is developed to locate source of damage inside of concrete. However, the AE signal is interfered by much noise, which makes the determination of first time amplitude of AE signal is hard to be carried out. In fact, the determination of this parameter is a significant part for locating the source of damage in concrete. Therefore, one of the denoising methods called wavelet based denoising is proposed. In this case, some wavelet bases function are investigated to find out the proper wavelet bases function to perform the denoising of AE Signal. From the experimental data, the best wavelet basis function for this case is Coiflet, which is shown by providing the best SNR than the other wavelet families. In addition, the determining cracks locations on concrete can be performed easier on denoised AE signal than on noisy AE signal.

Abstrak :
Electromagnetic theory offers fascination and challenge from both a physical and a mathematical perspective. This monograph contains the newest results on the use of electromagnetic probes to interrogate dielectric material structures for material properties and geometry. This volume systematically exploits interface phenomena, the electrodynamics of material responses, and time dependent interrogating signals in an integrated manner. The authors begin with basic electromagnetics, such as Maxwell's equations, and present modeling, theory, and computational results. The book's strengths include a clear discussion of materials properties from the electromagnetic point of view, a careful formulation of the imaging problems addressed, rigorous treatment of mathematical issues, and useful illustration of computational methods and results. While confined to internal vision in one-dimensional settings, this volume will stimulate further developments in internal vision to include two- and three-dimensional interior assessments. It is an excellent and robust source of applied mathematics and engineering research challenges for the future. Imaging technology stands to benefit much from this research on low energy electromagnetic radiation. The use of electromagnetic pulses interacting with specially placed reflective surfaces, whether solid or acoustic, is a new dimension that will substantively impact medical imaging, subsoil investigation, and structure evaluation.

Abstrak :
Fenomena yang sering ditemukan di lapangan adalah masalah partial discharge pada isolasi khususnya bushing transformator yang seharusnya mampu untuk menahan tegangan tembus yang telah ditentukan. Namun pengukuran dan pendeteksian partial discharge sebagai langkah preventif masih jarang dijumpai, sehingga berakibat pada kegagalan total pada isolasi. Pada penelitian ini dibahas tentang kegagalan isolasi baik padat, cair maupun gas yang merupakan faktor penting terjadinya partial discharge. Bushing merupakan peralatan persambungan yang merupakan titik lemah dari sistem tenaga listrik dan rentan terhadap kegagalan. Sehingga disusunlah berbagai metode untuk pendeteksian partial discharge ini seperti Dissolved Gas Analysis (DGA), pendeteksian emisi akustik, ultrasonik dan infra merah. Pada penelitian ini digunakan kombinasi monitoring partial discharge dengan menggunakan metode emisi akustik dan infra merah yang menunjukkan kemunculan sinyal emisi akustik dengan frekuensi-frekuensi tinggi pada partial discharge dengan energi yang lebih rendah. ......In field work, the most occurrance phenomene is partial discharge on isolation especially for isolation in bushing transformator which should able to resist the penetration voltage that have determined before. However, measurement and detection of partial discharge as preventive step is rare to do, so it can cause a total failure in isolation. This research is purposed to explain more about a total failure on solid, liquid, and gas isolation which is an important factor in partial discharge occurance. Bushing is a conjuction tool which is a weak point from electricity energy system and vulnurable with failure. Therefore, there are several method to detect partial discharge such as Dissolved Gas Analysis (DGA), acoustic emission, ultrasonic dan infra red. In this study used monitoring partial discharge with combining acoustic emission and infrared that show partial discharge of low energy create acoustic emission signal of higher frequency.