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Transformer Vibration Technique is considered an effective method to monitor structural elements of transformers, in particular, to detect loose or deformed windings. As it is well known, vibrations vary with the sensor location on the transformer tank, which makes the number and the placement of sensors critical aspects for fault detection. In this paper, we investigate this issue by analyzing vibration spectra collected from various sensors installed on the tank of a typical oil filled power transformer operating under two limit cases, namely absence or presence of clamping looseness on windings. Support Vector Machines (SVM) are employed and an extensive analysis is performed to understand the informativeness of data corresponding to various sensors so as to figure out the appropriate number of sensors and their best location. This way fault detection is eventually achieved with a reduced and optimized number of sensors, resulting in a significant saving of time and costs.

Degradation of electrical insulation due to the oil-paper insulating system is one of the main factors that affect power transformer service life. Although the end of life failure is inevitable, the life of the insulating paper can be maximized through careful monitoring and maintenance. In this paper an optical SPR sensor is reported for high sensitive detection of a chemical marker of the transformers’ insulating paper degradation. Temperature tests were carried out on oil–paper specimens representative of the solid insulating system of transformers, subjected to initial different drying processes and successively exposed to aging temperature. A comparative analysis with standard methods (HPLC—High Performance Liquid Chromatography) confirms that the chemical concentrations detected in oil–paper sampling of different specimens with optical SPR sensors are in good agreement with those measured by standard techniques.

The use of Nanostructured SPR sensors on Plastic Optical Fibers opens new challenges, because in an SPR sensor made by a continuous metal layer, the sensor’s response is basically related to the metal properties at optical frequencies and to the waveguide characteristics. On the other hand, when a Nanostructured SPR sensor is used, the behavior is also related to the geometric parameters of the Nanostructures. Working on them it is potentially possible to tune the sensor’s behavior. In this work the Authors present a numerical investigation in order to evaluate the behavior of two different SPR Nanostructured platforms, made by “long” gold Nanorods, and comparing them to an SPR sensor with a continuous gold layer. The difference between these two Nanostructured platforms is the orientation of the Nanorods, with respect to the light’s propagation direction. The numerical results seem to indicate an increase of the sensitivity, when an SPR Sensor with long Nanorods is used, with respect to the sensor made by a continuous gold film, with some benefits.

In this work the feasibility of an optical method for an early and high sensitivity detection of chemical agents in oil-filled power transformer is reported. It concerns the assessment of accelerated ageing of transformer insulating systems, primarily constituted of oil, paper and cellulose through an online detection of cellulose degradation by-products. The proposed optical device exploits the Surface Plasmon Resonance (SPR) excitation in a plastic optical fiber (POF) platform. High selectivity is obtained by a joint detection with a Molecularly Imprinted Polymer (MIP) layer, very specific for one of the most significant indicators of the transformer possible failure, furfural, in contact with the SPR active surface. Preliminary results of tests, carried out on calibrated furfural concentration diluted in transformer oil, confirm the feasibility of the proposed optical approach.

An innovative detection prototype, developed to improve the reliability of distribution networks is described. It is based on a multisensing approach including three different types of fiber-optic sensors. These sensors are based on different detection principles to measure, respectively, light ignition, sound pressure, and ozone changes produced by predischarge phenomena on medium voltage (MV) electrical equipments. A multifunctional software interface was developed to manage simultaneous acquisition and processing of all signal outputs. Preliminary tests were performed inside a MV switchboard inducing defects to simulate predischarge phenomena. A first analysis of simultaneous responses of the three sensors confirmed the feasibility of this combined approach as a potential diagnostic tool to assess the condition of MV electrical components.

Microdochium nivale carbohydrate oxidase was produced by heterologous recombinant expression in Aspergillus oryzae, purified and crystallized. The enzyme crystallizes with varying crystal morphologies depending on the crystallization conditions. Several different crystal forms were obtained using the hanging-drop vapour-diffusion method, two of which were used for diffraction measurements. Hexagon-shaped crystals (form I) diffracted to 2.66 A resolution, with unit-cell parameters a = b = 55.7, c = 610.4 A and apparent space group P6(2)22. Analysis of the data quality showed almost perfect twinning of the crystals. Attempts to solve the structure by molecular replacement did not give satisfactory results. Recently, clusters of rod-shaped crystals (form II) were grown in a solution containing PEG MME 550. These crystals belonged to the monoclinic system C2, with unit-cell parameters a = 132.9, b = 56.6, c = 86.5 A, beta = 95.7 degrees . Data sets were collected to a resolution of 2.4 A. The structure was solved by the molecular-replacement method. Model refinement is currently in progress.

In the framework of the new electrical power system management, a relevant role could be played by sensors and sensor network. The application of low-cost sensors could efficiently provide real time information on the ageing condition or on anomalous operation of electrical components of the new Medium Voltage (MV) network; this could prevent possible dangerous situations affecting the reliability of the distribution network itself. This paper reports two examples of development of optical sensors based prototypes for the diagnostic and monitoring of MV electrical components. The first one is a predischarge monitoring device for MV switchboards, which is based on three different optical sensors (optical, acoustic and chemical sensors). The simultaneous analysis of responses of these sensors is managed through a software LabView interface to improve the effectiveness of the diagnostic detection. The second one is a prototype based on miniaturized optical accelerometers for measurements of the vibration fingerprint of a Medium Voltage/Low Voltage (MV/LV) transformer to assess the mechanical integrity of its structural components.

This work describes a fibre optic device suitable for generating a trigger signal for a Medium Voltage substation monitoring system. It is based on the use of a low-cost transparent electro-optic ceramic for tracking electric field/voltage changes at the electric network frequency (50/60Hz). Results of tests carried out on a preliminary optical sensor, performed by means of a Voltage Calibrator, were in good agreement with the modelled sensor response to AC and DC voltages. This confirmed the effectiveness of the proposed model approach. Through simulation sensor parameters and layout were optimised for implementing a robust, low cost and easy installable optical device able to properly trigger a set of optical diagnostic tools for Medium Voltage switchboards.

This paper describes an assembled optical prototype for measurements of vibration of a distributing transformers tank. It consists of optical MEMS accelerometers, an acquisition unit wireless connected to a remote PC. A SW interface was developed to simultaneously control configuration settings of input channels, the display on the PC screen of acquired data and their storage. Preliminary tests were performed on a conventional type distribution transformer (30kVA); results of comparative analysis with standard piezoelectric accelerometers used as references confirm the feasibility of the proposed approach1.

This paper describes the application of a double-sided approach to assess the spent life fraction of thermal barrier coatings (TBCs) at local positions of ex-service blades with NiCoCrAlY-Re bond coat and EB-PVD TBC. A life prediction code implemented with inverse problem solution routines was applied to determine the mean local temperature. On the single blade, large differences (>150°C) of mean local temperature were estimated between regions just after the cooling holes and far from them. A self-developed portable photostimulated luminescence piezospectroscopy (PLPS) instrument was also applied and the coating spent life fraction was evaluated with a recently proposed PLPS diagnostic parameter. The spent life fractions evaluated from mean local temperature values were in good agreement with those estimated from PLPS measurements. Lower spent life fractions were found in well cooled regions of all blades, while higher spent life fractions were calculated at the hottest positions of the blades, particularly on components coming from a plant with a double number of starts. The results confirm the reliability of the PLPS technique and its diagnostic capability also for NiCoCrAlY-Re bond coats; both local differences on the single component and blade-to-blade variations in coating spent life can be evidenced in a nondestructive way.

The application of a fibre optic sensor for ozone detection in MV switchboard is evaluated. The sensor is based on the differential measure of the absorption in UV and visible spectral bandwidths. The layout exploits the use of an optical retro-reflector, to improve the detection sensitivity. Preliminary tests were performed in comparison with another calibrated system to assess the sensitivity and the linearity of the innovative sensor (0.1-10 ppm). Further results of tests carried out on a laboratory mock-up simulating predischarge phenomena are discussed confirming the compliance of the main features of the assembled system with application requirements.

A fiber-interferometric sensor realized with standard telecommunication components operating at 1550nm is developed to detect acoustic emissions from partial discharges in oilinsulated transformers. Sensor performance is compared with typical electric measurement in realistic harsh environment.

a previous paper', it develops the concept that both the reference beam and the sensingbeam must be conveyed along the same single -mode polarization -maintaining fiber. In such away a high noise -rejection ratio for any environmental perturbation is obtained2.The above requirements are to be added to the others related to the working conditions