International conference Diagnostika 13 Conference on Diagnostics in Electrical. Submitted to PCIM Conference, Nuremberg, Germany (2010). Daa _ecov.asp [5] J.

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SFRA MEASUREMENTS It is necessary to know all factors influencing the shape of frequency responses for exact interpretation of frequency responses and identification any mechanical damage that may occur during running of the transformer. As the primary winding has not neutral terminal it is not possible to measure winding according to the methodology A-N, B-N and C-N, but we have to use a methodology for measuring according to the delta connection.

Another factor that influences the shape of frequency responses is secondary windings connection in zig-zag. The impedances, which constitute measured circuit of primary winding (as determined by the methodology of measurement), are in this case always windings consist of two phases.

The impedances of the third phase of the primary winding (the one that is not currently measured) and impedances of secondary winding coils have also the influence on the shape of the frequency responses. The compilation of a complete spare scheme required to simulate in wide range of input frequencies would be therefore very difficult. And that is why in this article we will focus on practical measurement and correct interpretation of the frequency responses measured on the transformer. The basic methodology SFRA measurements is based on measuring described in 1. The measurement of the primary winding is different, due to the fact that the star connected winding has not neutral terminal.

Therefore, we have to measure as though it was connected to the delta winding (Tab. It is important to note which impedances impact on the measured frequency responses at the interpretation of them. TABLE OF SFRA MEASUREMENTS 1. Open circuit 22 kv 400 V Test 1 Test 2 Test 3 Test 4 Test 5 Test 6 A B B C C A a n b n c n 2.

Short circuit shorted a b c (ssek) shorted A B C (sprim) Test 7 Test 8 Test 9 Test 10 Test 11 Test 12 A B B C C A a n b n c n 3. Interwinding measurement Test 13 Test 14 Test 15 A a B b C c Fig. Open circuit tests of primary windings A-B (black), B-C (green), C-A (blue). 3 it can be seen that the course of frequency responses has not a standard shape, the waveform is characterized with distortion and major signal noise to the frequency of 10 khz.

An inexperienced technician could evaluate waveforms as fault at a glance, or he would their shape attributed to the internal noise of measurement device. However, this may not be true. For this type of distribution transformer it is very problematic to assess if the fault was measured or not. We have a look for additional assessment at the courses measured for the secondary winding with open circuit methodology (Fig. Open circuit measurements of secondary winding: a-n (green), b- n (blue), c-n (red) As the secondary winding is connected to the zig-zag and the frequency responses are the same for phase b and phase c.

This situation results from the arrangement of the transformer windings on its core (Fig. The coil of phase (a) is loaded on the first and third column of the core.

The junction of both parts of the coil phase (a) has longer conducting way as the coils of phases (b) and (c).therefore the impedance of phase (a) has a different value and a different shape over the frequency range up to 10 khz. We have found by measurement of six same transformer with secondary winding connected to the zig-zag that the frequency responses are identical with the frequency responses on the Fig.

4 in the case when the transformer is without fault. Then the frequency response for phase (b) and phase (c) to 10 khz are identical and frequency response for the phase (a) is different. If there is difference between all the phases, it means an internal fault. When the fault on transformer occurs, the frequency responses are reflected in other measured responses.

For the exact measurement of the transformer is useful interwinding methodology according to the article 2.8 of norm IEC The measurement results are shown in Fig. The waveforms are in frequency range up to approx. 550 Hz characterized with distortion and major signal noise. It is due to the fact that impedance of the circuit of the measured transformer consists of winding resistance, which is in this case infinitely large, because the primary and secondary windings are not conductively connected. The frequency responses in this case are influenced by inductive and capacitive couplings between windings.

The inductive and capacitive couplings will 50. 54 low losses ideal for broadband applications; low thermal coefficient of dielectric constant. Typical applications of these materials are RF identification tags, automotive radar and sensors etc. 55 temperature was 10 minutes.

Behavior of filter (frequency domain characteristic) was measured after 150, 300, 600 and 1300 cycles. High Temperature Operation Life HTOL test HTOL tests were done based on test method standard JEDEC JES22-A108. Four microstrip filters fabricated using different substrates were exposed to constant temperature +125 C. Scattering parameters of filters were measured after 200 and 400 hours 8. TEST RESULTS Vector Network Analyser (VNA) with two ports was used for measurements in frequency range from 10 MHz to 6 GHz. Test port cables were ended with SMA female connectors and SMA male connectors were soldered after each period of tests.

Results of temperature cycling tests Fig. A, Forward transmission coefficient (S21) of filter on substrate RO4003C after temperature cycling tests; b, Zoomed characteristic in range from 2 GHZ to 5.2 GHz (0 db to -9 db) Properties of notch filter fabricated on dielectric material RT/duroid5880, shown in Fig. 5, are significantly changed after temperature cycles. Frequency domain characteristic of microstrip notch filter after temperature cycling tests does not have bandstop properties. A, Forward transmission coefficient (S21) of filter on substrate RO3003C after temperature cycling tests; b, Zoomed characteristic in range from 2 GHZ to 5.2 GHz (0 db to -7 db) Frequency domain characteristic of notch filter on dielectric substrate RO3003C, shown in Fig. 3a, are slightly changed after temperature cycles. 3b frequency characteristic is zoomed, after 300 cycles attenuation up to -6 db in range from 2.6 GHz to 3.1 GHz is achieved.

This attenuation may be caused by resoldering of connectors, because after 600 and 1300 cycles it is not measured. 4a measured forward transmission coefficient of filter based on RO4003C is shown. After 150, 600 and 1300 cycles attenuation up to -8 db is measured in range from 3 GHz to 4.1 GHz. After 300 hours attenuation in Wi-Fi area is decreased from -42 db to -34 db.

Zoomed characteristic is shown in Fig. Change of attenuation which appeared after 150, 600 and 1300 cycles is not measured after 300 temperature changes. Thus, it is supposed, that inaccuracy in process of connectors resoldering could cause it. Forward transmission coefficient (S21) of filter on substrate RT/duroid5880 after temperature cycling tests. 6a forward transmission coefficient of notch filter made from dielectric substrate RT/duroid6010LM is shown. Properties of microstrip filter after temperature cycles are changed. 6b zoomed frequency characteristic is presented.

Beyond 2.5 GHz attenuation is noticeable up to -13 db. These similar attenuated bands appear periodically and they are spread over frequency from 2.5 GHz to 4 GHz. 59 Table 1 shows SunTech branch calculated values for each month incident solar energy on an area of 1m 2 H I,m obtained from from measured solar irradiance G I in the plane of panel using pyranometer, net SunTech branch energy E A,m and average monthly efficiency η A,m during power generation.

SunTech branch monthly energy production, solar irradiance and average efficiency. Month H I,m kwh.m -2 E A,m kwh η A,m % november ' december ' january ' february ' march ' april ' may ' june ' july ' august ' september ' october ' november ' december ' january ' february ' march ' Figure 1 shows incident solar energy dependence during the monitored period and monthly average temperature with its standard deviation, measured on the back site of the panels. The year 2012 yielded the total solar energy 1406 kwh.m -2 in the given location. In February 2012 was recorded the lowest temperature (-21.9 C) and the highest temperature in August 2012 (62.7 C). Stated in Table 1 for a given month. The year 2012 yielded the total solar energy incident on the active SunTech area 2231 kwh. Energy production of SunTech branch for year 2012 was approx.

Monthly incident solar energy at SunTech branch active area and energy production of SunTech branch. Figure 3 and figure 4 shows temperature, energy production and average efficiency of SunTech branch during energy production for each month. According to this dependence it is clear, that the warm summer months reducing the efficiency of solar energy to electrical energy conversion, although the yield is still higher in sunny summer months (see Figure 5). Average efficiency values related to each month are shown in the Table 1.

Minimum average efficiency was reflected in August 2012 (7.77%) and maximum in November 2012 (10.27%). The maximum energy production of SunTech branch was in May 2012 (23.98 kwh) and the minimum in December 2011 (4.25 kwh). Maximum percentual energy production covers May 2012 (12.96%). The evolution of SunTech energy production branch is shown on Figure 6. Monthly incident solar energy on an area of 1 m 2 on the monitored PV system site and average monthly panel temperatures with standard deviation y-error bars. Dependence on Figure 2 illustrates graphical comparison of monthly incident solar energy recalculated to active area and monthly energy production of SunTech branch.

This ratio is the calculated average efficiency Fig. Monthly energy production and monthly average efficiency. 79 been used in order to guarantee the electrical conductivity.

For the test procedure each of the three electrodes has been connected to high voltage. Moreover, the counter electrode is a board that is connected to ground. By adjusting the space between tip and Fig. Spherical-shaped tip countertop and keeping it constant at 40 mm, a different characteristic of the PD inception voltages at which the pressure varies from 1 bar (ambient pressure) to 6 bar (5 bar gauge pressure) can be demonstrated. A space of 40 mm has been chosen for both the cone-shaped tip and the wedged shaped tip. For the spherical, however, a space between tip and countertop of 60 mm has been chosen, because corona discharges and lighting effects could be observed during the measurement at a space of 40 mm.

Thereupon, high voltage has been increased until PD can be measured in the negative half wave first, as the tip is connected to HV. Afterwards, 1.1-times of the inception voltage has been adjusted and the PD pattern has been recorded over a time slot of twenty seconds.

Moreover, the PD magnitude has been measured as well. After that, high voltage has been increased furthermore in order to measure the PD inception voltage in the positive half wave. After adjusting 1.1-times of the inception voltage, the PD pattern has been recorded once more and the PD magnitude has been measured. After measuring the PD inception voltage, the PD extinction voltage needs to be measured as well. Consequently, high voltage is decreased until no more PD can be measured in the positive half wave. This is the PD extinction voltage of the positive half wave. With continuing decreasing high voltage to the point where the partial discharges adjourn as well, the PD extinction voltage of the negative half wave can also be found.

This test procedure has been executed for each of the three tips introduced above and has been repeated in three different isolation gases, i.e. Air, oxygen and nitrogen. Apart from this, oxygen and nitrogen have been mixed where the volumetric content of nitrogen has been varied from 0% to 100%. A space of 40 mm has been adjusted for the cone-shaped tip. The pressure has been kept constant at 1 bar. Both the PD inception voltages and the PD extinction voltage of both half waves have been measured, as explained above. TEST RESULTS All of the three test setups have been tested in different isolation gases where pressure has been varied from 1 bar to 6 bar.

For each of the three setups, the PD inception voltage in both the positive and the negative half wave have been plotted over pressure. The PD inception voltage 1 will be referred to as V inc,1 (continuous line in all figures) and the PD inception voltage 2 will be denoted by V inc,2 (dashed line in all figures). The PD extinction voltages are referred to as V ext,1, respectively V ext,2, as far as the PD extinction voltage in the positive half wave is concerned. Characteristic of PD inception voltages of a cone-shaped tip in diffenerent isolation gases under pressure A. Cone-shaped tip in different isolation gases under pressure The test results of the cone-shaped tip are presented in fig. By varying the pressure, V inc,1 in air (red continuous line) increases nearly linearly from about 2.6 kv to 7 kv.

At ambient pressure V inc,2 is approximately 13.3 kv. After that, V inc,2 decreases up to a pressure of 4 bar. Then, PD occurs nearly simultaneously in both half waves.

Starting with 3 kv, V inc,1 rises linearly over pressure up to approximately 7.5 kv, just as in air. V inc,2 at a pressure of 1 bar is about 4.8 kv. Then it rises slightly up to a pressure of 3 bar where it has its maximum of 9.3 kv. At 3.5 bar, PD occurs at around 7.1 kv, thereupon, starting from 4 bar, PD in both half waves begin simultaneously.

In the negative half wave the PD inception voltage behaves in nitrogen just as in oxygen: it increases almost linearly. The inception voltage in the positive half wave starts at ambient pressure 7.5 kv. Thereupon it increases up to a pressure of 2.5 bar where a maximum of around 10 kv occurs. After that PD occur simultaneously in both half waves. 6 shows the PD pattern of the cone-shaped tip at a pressure of 2 bar at V=1.1V inc,2 in oxygen, air and nitrogen.

Both in the positive and in the negative half wave the PD pattern are very different in the different gases and can easily be distinguished. Wedged-shaped tip in different isolation gases under pressure While using the wedged-shaped tip, a quite another behavior of the PD inception voltages could be determined, Fig. Characteristic of PD inception voltages of a wedged-shaped tip in diffenerent isolation gases under pressure 79. 86 Dielectric measurement of a nanocomposite material at an early stage of accelerated ageing Marian Klampar 1), Karel Liedermann 2) Department of Physics, Faculty of Electrical Engineering and Communications, Brno University of Technology Technicka 10, Brno 61600, Czech Republic, 1) tel:, 2) tel:, Abstract This article discusses measurements of dielectric spectra in an electrical insulating nanocomposite at an early ageing stage. The focus of the research was on electrical and chemical changes, accompanied by the comparison of our results with those provided in the literature.

The latest measuring technology available was used, most notably Novocontrol Alpha A analyzer, which was used to measure samples in the frequency range 0.1 Hz - 6 MHz, together with the Quatro Cryosystem, which allowed to measure samples under temperatures ranging from 120 K to 400 K. Partial changes of relaxation maxima during measurement were observed. Keywords dielectric mesurement; epoxy resin; fast ageing; nanocomposite; Novocontrol I. INTRODUCTION Currently, one of the most popular tools for molecular dynamics analysis of material is dielectric relaxation spectroscopy (DRS) 1. The result of advance in research and development of measurement instruments is that now it is possible to do measurements in the frequency range from 10-6 Hz to Hz and in the temperature range from some 260 C to about 700 C.

DRS can indicate, which temperature, frequency or formulation ranges are suitable or not, for practical application. DRS can also elucidate microscopic mechanisms underlying the changes arising in the course of material aging 6. Nanocomposites have been a subject of intense studies over the past twenty years 9, 10.

Currently there is a trend to a transition from the stage of purely scientific research to their practical application in engineering systems. Practical application requires stability in operation, absence of later defects and also an absence of substantial changes of their properties brought about by ageing under usual operating conditions (higher temperatures, humidity or presence of external electrical fields). One of the currently investigated application areas for nanocomposites is advanced electrical insulation 4. The application of nanocomposites for electrical insulating purposes has both benefits and drawbacks.

The benefits include an ability of the nanocomposite material to withstand electric discharges as nanoparticles in composites act as locally dispersed barriers against the propagating electrical trees 8. For the illustration of the electrical tree propagation prevention mechanism, see Fig 1 below: Fig. Illustrative example of the increased resistance to electrical tree propagation in a nanocomposite, from 8 One of the major drawbacks associated with the use of nanocomposites is a large area of internal oxide epoxy interfaces. These large internal surface areas exhibit discontinuities between the properties of nanoparticles and surrounding matrix, and this may act as a source of defects.

Moreover, the ageing, both thermal and electrical, may bring about an increase in defect concentration 7. Therefore, it seems desirable to examine the properties of nanocomposites in the course of ageing prior to any largescale deployment of them in electrical engineering industry. As ageing at standard operating conditions takes too much time, in this case it was replaced by an accelerated ageing at a higher temperature. SAMPLES AND BACKGROUND In this case, research was focused on epoxy resins with different additives, from non-conductive TiO 2, Al 2 O 3, SiO 2 to conductive WO 3.

These samples were cast on a mold, specially made for this purpose. The mold had to be reheated as in the past, and can be seen in Fig. Prior to manufacture, epoxy resin Araldite CY 228, hardener HY 918, flexibilizer DY 045 and curing accelerator DY 062 were mixed together in shares and steps set by the technical documentation of the supplier, Vantico Ltd. (formerly Ciba Specialty Chemicals, Oxford, UK) 2. Two solutions were prepared: the first solution consisted of the mixtures of epoxy resin, flexibilizer, accelerator and nanofillers; the other solution consisted of pure hardener.

One sample was left without the addition of nanofiller; in that case the first solution contained the mixtures of epoxy resin, flexibilizer and accelerator. Nanofillers TiO 2, SiO 2, Al 2 O 3 and WO 3 were supplied by Sigma Aldrich.

Their purities were different TiO 2 was 99.7% pure, SiO%. Purity of Al 2 O 3 and WO 3 were not mentioned in documentation. Even particle size was different among nanofillers SiO 2 only 5 15 nm, TiO 2 86 87 approximately. 94 Influence of Firing Process on LTCC Characteristic Alena Pietrikova 1), Juraj Durisin 1), Igor Vehec 1) 1) Department of Technologies in Electronics, Technical University of Kosice, Slovak Republic, 1) tel:, 1) tel:, 1) tel:, i. Abstract The paper describes results of investigations concerning the mechanical behavior and material characterization of different DuPont tapes. Firing is critical to the development of composite material characteristics.

PEO 602 firing furnace with controlled atmosphere was used for firing two types of Low Temperature Co-fired Ceramics (LTCC from DuPont 951 and DuPont 9K7) using various firing profiles. This paper deals with X Ray diffraction used for identification of crystallographic components and phases based on various firing profiles. In order to achieve crystallization in the material, LTCC samples were heated at a rate of 13.5 C (or 0.7 C/ min) held at temperature 850 C (or 890 C) within 20 min and cooled at a rate of 20.4 C/ min (or 1.62 C/min). Additional mechanical testing methods were used to evaluate the composite material. Keywords LTCC, 951 DuPont, 9K7 DuPont, four-point bend test, X-ray analyse I. INTRODUCTION LTCC (low-temperature co-fired ceramic) is a multilayer platform technology that is used to make components, modules or packages for e.g. Wireless, automotive, military, biomedical and photonic markets.

This technology offers unique benefits and cost effective solutions for applications where high electrical performance, miniaturization, stability and reliability are key issues. Benefits of LTCC technology is flat frequency response and low loss up to millimeter waves, high conductivity metals (Ag, Au), integrated functions, excellent radiation management, low thermal coefficient of resonant frequency, high packaging density, high layer count, fine-line patterning and precise line definition, 3D structures, good CTE matching between the LTCC dielectric and semiconductors low temperature brazing for hermetic sealing, fine-line capability including screenprinting and photoimaging technologies. Our work in laboratory has focused on the development high-frequency application of the LTCC substrate for low loss stabile dielectric requires the development of band pass filters for UWB radars. Investigation of mechanical properties in correlation with structure under various firing profile play important role. The ceramic materials used in the work are two commercially available green tapes: DuPont 951 and DuPont 9K7. The GreenTape 9K7 ceramic tape dielectric represents a major technological advancement for use in high frequency applications. Effect of multiple firing on microstructure and mechanical properties were undertaken to understand the differences in performance.

X-ray diffraction analyze and investigation of responses of LTCC when subjected to 4-point bend were presented based on experimental results of this study. EXPERIMENTAL PROCEDURE Firing is critical to the development of composite material characteristics. The dissolution of the ceramic particles (Al 2 O 3 ) in the glassy phase has an important influence on the viscosity of the melt during the firing. Sintering occurs through the viscous flow mechanism in which liquefaction of glass has a dominant role. We propose various firing profile for our experiments because it should have important role in mechanical and dielectric properties of LTCC. Our investigation is aimed to determination of density and micro strain and by this manner contributes to analyse of shrinkage of LTCC as unwanted property of LTCC. Before sintering, 5 green tapes of 951 ceramic were laminated, and then cut from laminated sheet, using a steel rule cutting die.

The laminating process follows the firing processes for each LTCC sample. Four types of firing profiles were applied for DuPont 951 ceramic: F1 recommended standard profile under data sheet, F2 double repeated firing profile, F3 triple standard profile, F4 adjusted standard profile with increasing max. Temperature from 850 to 890 C. DuPont 9K7 as a new type of LTCC was fired under data sheet recommendation (see Fig.

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1 Temperature profiles applied for 951 (F1, F2, F3 and F4) and 9K7 DuPont LTCC 94.