100 kV DC high voltage divider having lower than 100 ppm measurement uncertainty

Bu makalede, 100 ppm ölçüm belirsizliğine sahip, kalibrasyon standardı olarak kullanılmak üzere tasarımı ve yapımı gerçekleştirilen 100 kV’luk bir yüksek doğru gerilim bölücüsüyle ilgili yapılan çalışmalar sunulmuştur. Yüksek doğru gerilimlerin ölçülmesinde yaygın olarak dirençsel gerilim bölücüler kullanılır. Bunların çevirme oranları, kesin olarak bilinmeli ve gerilime bağlı olmamalıdır. Uygulanan gerilimin yüksekliğiyle çevirme oranı, temelde üç faktöre bağlı olarak değişir. Bunlar, dirençlerin ısınmasına bağlı olarak direnç değerlerindeki değişim, kaçak akımlar ve korona boşalmalarıdır. Gerilim bölücünün yapımı, bu faktörler hesaplanarak gerçekleştirilmiştir. Yapım sonrasında performans deneyleri yapılmıştır. Deney sonuçları ile teorik sonuçların uyumlu oldukları görülmüştür. Son olarak gerilim bölücünün belirsizlik bütçesi oluşturulmuştur.Anahtar Kelimeler: Yüksek doğru gerilim bölücüsü, ölçüm belirsizliği, yüksek gerilim izlenebilirliği.The aim of this paper is to show that the designing and constructing of the direct current (DC) high voltage divider having lower than 100 ppm (part per million) measurement uncertainty (k = 2) for using as a standard divider at 100 kV. The ratio of a resistive standard divider used for precisely measuring DC high voltages should have been known accurately and independent of voltage. A change in effective resistance of a divider with voltage may be due to combination of three factors. These are heating of entire resistance wire related to temperature coefficient, current leakage which increases with voltages through the insulation material and corona discharges may occur at location of high electrical field along to the entire resistor. The aim of this study is to construct an accurate DC high voltage reference divider considering these factors. This divider is constructed by considering these factors, theoretically. After construction of the divider, performance tests are carried out experimentally. These are stability, linearity, temperature distribution, corona, leakage current, partial discharge and scale factor tests. The results obtainedfrom the tests have been compared with theoretical calculations and it has been shown that the results are compatible. Finally the uncertainty budget of the high voltage divider has been formed and uncertainty of the divider has been obtained to be 66 ppm. Keywords: DC high voltage divider, measurement uncertainty, high voltage traceability

Computation of corona inception voltage by charge simulation method

Bu çalışmada, atmosfer basınçlı havada çubuk-düzlem elektrot sisteminde, pozitif doğru gerilimde statik elektrik alan dağılımı, elektron çığı ve korona başlangıç gerilimi, gazlarda boşalma olaylarının sayısal benzetimi amacıyla geliştirilen ve Yük Benzetim Yöntemi'ne dayanan özgün bir yazılımla hesaplanmıştır. Yük Benzetim Yöntemi'nde elektrotların benzetiminde noktasal, çizgisel ve halkasal yükler kullanılmıştır. Elektron çığının halkasal yüklerle modellenmesinde elektronların geçiş süresi, yük yerleri ve yarıçapları yeni bir yöntemle hesaplanmıştır. Anoda yaklaştıkça elektrik alanın, dolayısıyla elektronların hızlarının artmasıyla çarpışma noktaları arasındaki uzaklıkların azalacağı ve çarpışma sayısının artacağı göz önünde tutularak korona başlangıç gerilimi daha doğru hesaplanmıştır. Sonuçlar, geliştirilen yazılımın başarımını ve önerilen yaklaşımın uygunluğunu ortaya koymaktadır.Anahtar Kelimeler: Elektrostatik alan hesabı, korona başlangıç gerilimi, yük benzetim yöntemi.In this paper, numerical simulation of electrical discharge phenomena in gases has been made. Electric field distribution, electron avalanche and corona inception voltage of a rod-plane gap have been computed using a newly developed software. For electric field computations, Charge Simulation Method (CSM) has been used with point, line and ring charges. In the electron avalanche modeling, electron transit time has been computed in very small space intervals and summated, instead of dividing the distance between the critical field point and the collision point, by the electron velocity. So, radius and position of each ring charge and corona inception voltage have been computed more accurately by this new method. Collision points have been determined according to the value of integration of ionization coefficient. Then, ring charges with a homogeneous charge distribution have been positioned at these points. The charge quantity at these points is equal to the charge quantity of positive ions generated in this collision. The increase of electric field and the velocity of electrons, between critical field point and the anode have been taken into consideration. If the integration of ionization coefficient reaches a constant value of 18, then the applied voltage has been considered as the corona inception voltage. Results are in a good agreement with those found in the literature. So, the new electron avalanche modeling can be used for these computations.Keywords: Electrostatic field calculation, corona inception voltage, Charge simulation metho

Zamanla hızlı değişen gerilimlerde boşalma olaylarının incelenmesi

Improvements in technology had widened the use of electricity. The process beginning with direct current continued with alternative current. Wide usage had brought different requirements with. The natural effect of lightning and the disturbance effect of switching in electrical installation necessitated research on this subject. It?s necessary to have an idea on the behavior of electrical systems facing such an effect, before they are put into operation. This necessity had triggered generation of pulse voltages in laboratories. Pulse voltages generated gave the chance of performing tests on systems and components forming systems. In the course of time, pulse voltages have been generated not only for experimental objective, and also directly for industrial, medical, military etc. objectives. The microsecond and millisecond pulses reduced to nanosecond even picosecond pulses with the development in technology. Nanosecond pulses may be formed by EMP (ElectroMagnetic Pulse). EMP can be originated naturally in space; beside it can be formed artificially. A high altitude EMP can effect a wide area on earth. The most important disturbance effect of EMP is coupling to the conductors of electronic systems and equipments, entering the device and causing a breakdown or malfunction. EMP like pulses are usually nanosecond pulses. To examine the behavior of devices facing such a pulse, artificial EMP simulators are used. These simulators generate the electric and magnetic fields simulating EMP. In this study, the possible events that may take place when the EMP like nanosecond pulses reaches to the conductors and circuits of electronic devices are evaluated. In this study it is intended to perform conducted EMP tests directly on to the conductors. For this aim, a pulse generator with an output up to 10 kV peak value, generating a pulse with a risetime of about 50 ns and total duration of about 1000 ns is designed and constructed. The realized generator operates according to principle of a single stage Marx circuit. Accurate and reliable measurement of the fast voltage pulse is an important point to be considered. Different ways of measurement of the high voltage pulse is experimented. An oscilloscope with capability of sampling 4 GSa/s is used to scope the pulse generated. The high speed and the other technical benefits of the oscilloscope brought many advantages with. For simulating the circuit of electronic device, widely used seven different geometrical current ways are prepared on to the board made of Fr4. Fr4 is a fire rated electrical-grade, dielectric fiberglass laminate epoxy resin system combined with a glass fabric substrate. Series of pulses of different voltage level is applied by the generator on the sample board, and the flashovers between current ways are observed. Number of flashover occurred over the applied pulses is noted as a table. Data on this table versus the voltage applied is used to draw graphics, which can be evaluated as the fifty percent discharge curves of the electrodes. Another work performed on the sample board is the determination of the flashover points for different geometries. Arc points of the electrodes were observed visually during the tests; besides, the electrodes were investigated by an electron microscope. The experimental work performed is tried to be supported with theoretical analysis. For this aim, electrical field intensity and field distribution of the electrodes under the voltage applied is numerically analyzed. Analysis is performed on computer using FEMM program based on finite elements method. The expected point of flashover is the point where the maximum electrical field observed. Both the experimental study and the computer analysis gave the similar results. Current way electrodes set straight parallel has lower fifty percent discharge level when compared with parallel electrodes having angles or arcs. Among the seven different geometries, electrodes having 135° mutually has the minimum fifty percent discharge voltage level. On parallel electrodes, flashover takes place on the edges however electrodes with arcs or angular in shape flashes at these angle points. The electromagnetic interference radiated from the test setup is determined. For this aim, the emission of the system is measured by biconical antennas during the test for all seven geometrical current ways. One step further, the current induced by the emission coupled to a power cord 1 m away from the setup is measured and evaluated. Keywords: EMP, fast transient pulse voltage, surface flashover, current ways.Nanosaniyelik darbeler, EMP (ElektroManyetik Darbe) yoluyla oluşabilir. EMP uzayda doğal yolla meydana gelebileceği gibi yapay yolla da oluşturulabilir. Yüksek irtifada meydana gelen bir EMP, çok geniş alanları etkisi altında bırakabilir. EMP’nin en önemli bozucu etkisi, elektronik sistemlerin ve cihazların iletkenlerine girişimde bulunarak bunların içine ulaşması ve sistem veya aygıtların bozulmasına ya da yanlış çalışmasına neden olmasıdır. EMP benzeri darbe gerilimleri genel olarak nanosaniye süreli darbelerdir. Cihazların böyle darbeler karşısındaki davranışlarını incelemek için yapay EMP üreteçleri kullanılır. Bu üreteçler EMP’nin oluşturduğu elektrik ve manyetik alanları üretirler. Bu çalışma kapsamında EMP benzeri nanosaniyelik darbelerin aygıtların iletkenlerine ve elektronik kartlarına ulaşmaları durumunda meydana gelebilecek olaylar değerlendirilmiştir. Bu amaçla, yaklaşık 50 nanosaniyede tepe değerine ulaşan ve toplamda yaklaşık 1000 nanosaniye süren 10 kV’a kadar darbe gerilimi üreten bir üreteç tasarlanmış ve gerçeklenmiştir. Üreteç tek katlı Marx devresi ilkesi ile çalışmaktadır. Elektronik aygıtların devre kartlarını benzetmek için elektronik devrelerde sıkça karşılaşılan yedi farklı geometride akım yolu FR-4 malzemeden yapılmış devre kartına hazırlanmıştır. Darbe gerilimi üretecinden elde edilen gerilimlerle akım yolları arasındaki boşalma olayları incelenmiştir. Numune akım yollarında geometriye bağlı olarak boşalma noktaları belirlenmiş, uygulanan gerilimler ile elektrotların yüzde elli atlama eğrileri çıkarılmıştır. Yapılan deneysel çalışma, teorik hesaplamalar ile desteklenmiştir. Bunun için sonlu elemanlar yöntemi ile bilgisayar analizi yapılmıştır. Bu çalışma ile nanosaniyelik darbe gerilimine maruz kalan elektronik kartlarda geometriye bağlı olarak etkilenme üzerine yorum yapılmıştır. Anahtar Kelimeler: EMP, hızlı geçici darbe gerilimi, yüzeysel boşalma, akım yolları.&nbsp

2D and 3D numerical analysis of potential distribution around grounding electrodes

Topraklayıcıların çevresindeki potansiyel dağılımının bilinmesi, canlılar için hayati tehlike oluşturabilecek adım geriliminin genliğinin ve değişiminin bilinmesi açısından önemlidir. Bu çalışmanın amacı, farklı topraklayıcılar çevresindeki potansiyel dağılımını, sonlu farklar ve sonlu elemanlar yöntemleri ile, topraklayıcı boyutuna, geometrisine, konumuna ve toprak yapısına bağlı olarak incelemek ve güvenli çalışma koşullarını belirlemektir. Toprak özdirenci ile toprak dielektrik sabiti arasındaki ilişkiden yararlanılarak yerel ve mevsimsel etkilerle topraklayıcı çevresindeki toprağın cinsinin ve nemliliğinin değişiminin, topraklayıcı davranışına etkileri incelenmiştir. İncelemeler, topraklayıcılar çevresinde potansiyel dağılımlarının önerilen yaklaşım ve yöntemlerle kolay ve gerçeğe uygun olarak bulunabileceğini ve tehlikeli koşulları yaratmayacak şekilde topraklayıcıların tasarlanabileceğini göstermiştir. Anahtar Kelimeler:  Topraklama, potansiyel dağılımı, sonlu farklar yöntemi, sonlu elemanlar yöntemi.The aim of this paper is to show that, different models can be developed to determine potential distribution around different grounding electrodes and the computations on those models can be carried out more effectively by a new approach using Finite Difference Method (FDM) and Finite Element Method (FEM). In calculations, type and humidity of the soil surrounding the grounding electrode and differences in soil dielectric constants, are considered. Therefore, in this study instead of corresponding soil resistivity, soil dielectric constants are used. In this paper, potential distributions and step voltages have been computed in different coordinate systems for grounding electrodes which may have different shapes, different buried depths in the serial and parallel soil layers. A new technique called Cellular Equation Solution has been developed in MS Excel program using the FDM for computations of two and three-dimensional potential distribution. It has been shown that, large scaled equation systems can be established and solved easily and in a short time by this new method. Detailed studies on the models have been carried out with FEM for analyzing systems those models have been solved by the FEMM (Finite Element Method Magnetics) packet program. The results obtained using analytical and numerical methods have been compared and it has been shown that the results are compatible and the methods are applicable.Keywords: Grounding, potential distribution, finite difference method, finite element method.

The effect of DC voltage pre-stress on breakdown voltage of air under composite DC & LI voltage and test circuit: design and application

The use of HVDC systems is increasing in number due to technological innovations, increasing power capacity and increasing customer demand. The characteristics of insulation systems under composite DC and LI voltage must be examined and clarified. In this study, firstly, experimental circuits were designed to generate and measure composite DC and LI high voltage using a simulation program. The coupling elements used were chosen according to simulation results. Afterward, experimental circuits were established in the laboratory according to the simulation results of the designed experimental circuit. Then, breakdown voltages under composite DC and LI voltage for less uniform and non-uniform electric fields were measured with four different electrode systems for positive and negative DC voltage pre-stresses with different amplitudes. The 50% breakdown voltage was calculated using the least-squares method. Finally, 3D models were created for the electrode systems used in the experiments using the finite element method. The efficiency factors of electrode systems calculated with the FEM results were correlated with the experimental breakdown voltage results. Thus, the breakdown behavior of air under bipolar and unipolar composite voltages (CV) was investigated. In conclusion, the experimental results showed that very fast polarity change in bipolar CV causes higher electrical stress compared to unipolar CV

Investigation of impact of DC component on breakdown characteristics for different electric fields under composite AC & DC voltage

The valve side of the converter in the high-voltage direct current is subjected to mixed voltages such as composite AC & DC voltage. In this study, the effects of the homogeneity of electric field on breakdown voltage were investigated for different ±DC component amplitudes of the composite voltage. The field efficiency factor was calculated using mean and maximum field strengths for all of them. Variation of breakdown voltage of air was examined under the composite AC & DC voltage for different ratios ±DC. As one result of the study, the breakdown occurs at the positive half-wave of the AC voltage despite −DC voltage being applied due to positive corona discharge pulses. This breakdown point is named as the polarity change point. The breakdown voltage increases with the decrease of DC voltage component up to polarity change point in non-uniform electric field. In less uniform electric field, the AC breakdown voltage was measured slightly higher than the DC breakdown voltage. In less uniform electric field, as the ratio of the applied AC voltage to DC voltage increases, the breakdown voltage gradually approaches the AC breakdown voltage. This result is similar to the result obtained for the +DC component in non-uniform electric field experiments

analysis Of Partial Discharge Reference Source Under High Direct Voltage Conditions

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 1991Thesis (Ph.D.) -- İstanbul Technical University, Institute of Science and Technology, 1991Bir sivri uç-yarıküre elektrot düzeni olan referans kısmi boşalma (korona) kaynağı, yüksek gerilimde, sabit genlikli ve sıklıklı boşalma darbeleri üreten ve kısmi boşalma ölçme devrelerinin ölçeklenmesinde kullanılan bir düzendir. Alternatif gerilimde kullanım koşulları belirli olan bu düzenin, bu çalışmada, doğru gerilimde kullanım olanakları araştırılmış ve çalışma koşulları belirlenmeye çalışılmıştır. Referans korona kaynağında boşalma büyüklükleri ile elektrot düzeninin biçim ve boyutları arasındaki ilişkiyi incelemek amacıyla kuramsal ve deneysel elektrostatik alan incelemeleri yapılmıştır. Analitik alan incelemelerinde, yaklaşık hesap yöntemi, görüntü yükleri yöntemi ve sferoidal ve paraboloidal koordinatlar; sayısal alan incelemelerinde sonlu elemanlar yöntemi; deneysel alan incele melerinde de elektrolitik banyo ve yarıiletken kağıt yöntemleri kullanılmıştır. Yüksek doğru ve alternatif gerilimde yapılan kısmi boşalma deneylerinde, referans korona kaynağında boşalma büyüklüklerine siv ri uç eğrilik yarıçapının, elektrot açıklığının, sıcaklığın ve basıncın etkileri incelenmiş; kısmi boşalma ölçme frekansının önemi ve kaynağın çevreye yayınladığı radyo parazitlerinin uzaklık ve gerilimle değişimi araştırılmıştır. Deneysel incelemelerde, kuramsal incelemelerde de olduğu gibi, boşalma büyüklüklerine etkiyen en önemli etkenin sivri uç eğrilik yarıçapı olduğu görülmüştür. Yapılan incelemeler, referans korona kaynağının yüksek doğru gerilim koşullarında da kullanılabileceğini göstermiştir. The sensitivity and the calibration of partial discharge detection systems are important aspects of general subject of partial discharge measurements. Calibration of instruments measuring several discharge quantities in the complete test arrangement should be made by injecting short current pulses of known magnitude into the terminals the measuring circuit. The calibration can be made either in the low voltage mode or in the high voltage mode., Calibration in the low voltage mode is to supply an artifical discharge of known magnitude at the terminals of the detection circuit. This type of calibration devices are known as primary dis charge standard sources. Secondary discharge standards which are used in the high voltage mode are usually made from sources of natu ral discharges, i.e., surfaces discharges, internal discharges and corona discharges. Among these, corona discharges around a sharp point are the most suitable ones. One convenient type of corona discharge reference source (CDRS), which is suitable for direct connection in the high voltage test circuit, is a point-hemisphere discharge gap (Fig.l). The device consists essentially of a needle pointing into a hemisphere. Hemisphere electrode Fig.l. Corona discharge reference source. R=25 mm, r=0.05 - 0.5 mm. Under certain conditions, this gap will give a discharge magnitude which is constant to within +_ 10 %. The discharge level is dependent on the radius of curvature of the point. At the incep tion voltage one or two discharge pulses occur during each negative half-cycle of the 50 Hz sine wave. If the voltage is increased, the number of discharges (repetition rate) increases, but the dis charge magnitude remains constant. vıı Corona discharge reference source have been analyzed for alternating voltages. The discharge phenomena under direct voltage conditions takes approximately 10 nanosecond. This duration is extremely short, compared with the half period of a 50 Hz sine wave. Therefore, the discharge process at direct voltages can assumed to be the same with that at alternating voltages. The calibration of partial discharge measurements under high direct voltage conditions are almost done by primary discharge standard sources as in the high alternating voltage case. In this thesis, several characteristics and the operating aspects of the corona discharge reference source are investigated and demonstrated for high direct voltage conditions. It was aimed to show that the corona discharge reference source can be used as an alternative calibration source under high direct volt age conditions. Moreover, as an extension to alternating voltage studies, the variation of the corona inception and extinction volt age with the temperature and the pressure are determined experimen tally. The studies began with the theoretical analysis of discharge phenomena. Afterwards, potential and field analysis, which yield a close dependence with the discharge quantities (partial discharge inception voltage, apparent charge, repetition rate...) of corona discharge reference source have been conducted by theoretical and experimental methods. Finaly, several partial discharge tests at high alternating and direct voltages have been carried out and the results are compared both with eachother and with of those reported in the literature. Both the analytical and numerical electrostatic field calcu lations require the solution of Laplace (or Poisson) equation. Analytical methods can easily be applied in case of simple electrode configurations. However, most electrode systems in nature do not posses such a simple configurations. In case, one of the following methods must be applied: (1) Approximated solutions, (2) Coordinate transformations or conformal mapping, (3) Numerical methods, (4) Experimental methods. Since the corona discharge reference source yields a non uniform field, it is impossible to perform an exact analytical cal culation without coordinate transformation. Theoretical field analysis of corona discharge reference source have been done by approximated solutions, coordinate trans formations and numerical methods. In approximated solutions, point- hemisphere configuration of corona discharge reference source is transferred to concentric-hemisphere and sphere-plane electrode systems. The calculated maximum electric field strength and capa citance values of the electrode system are found to be nearly the same for both approximations. Coordinate transformation can be done by choosing the most adequate coordinate system for the electrode configuration. Prolate spheroidal and parabolic coordinate systems are preferred for corona discharge reference source and the solutions of Laplace equation are viii carried out in that coordinate systems. The point-hemisphere con figuration is considered a hyperboloid point-plane in prolate spheroidal coordinate system and two confocal paraboloids in para bolic coordinate system. In these coordinate transformations, utilization factor r) is obtained as: n = sin2(a/2).tanh 1 [cos(a/2)] cos(a/2) (1) for a hyperboloid point-plane configuration and ln(2p-l) n " 2(p-l) (2) for two confocal paraboloids. Where a is the top angle of point electrode, p is R/r as a geometrical characteristic. R and r are hemisphere radius and point radius, respectively. For the applied voltage U and electrode spacing a, the maximum field strength E^ may be calculated as: max E = U/a.n max (3) Among these coordinate transformations, parabolic coordinate system is more adequate for corona discharge reference source, because of the close similarity between a parabolic and a point electrode. Fig. 2 shows the equipotential lines (surfaces) calculated in para bolic coordinate system. Fig. 2. The equipotential lines calculated in parabolic coordinate system. Numerical methods have become more and more attractive with the increasing availability of modern high-speed digital computers, Among them, finite element method (FEM) is the most preferred one. The basic principle of the finite element method is to divide the entire solution domain into arbitrarily chosen finite elements and then to find a piece-wise solution of potential function in each element in which approximate potential function is expressed by a xx polynomal. Here, two dimensional and rotationally symmetric field produced by corona discharge reference source is examined by using triangular elements. The region of solution is divided into a nonuniform mesh by automatic grid generation. Cylindrical coordi nates are used for the formulation. The resulting sparse, simulta neous, lineer equation system is solved by successive over-relaxation method. Fig. 3 shows the equipotential lines and grid obtained from finite element method. Fig. 3. The equipotential lines and grid obtained from finite element method. Experimental field analysis of corona discharge reference source have been conducted both by electrolytic tank method and semiconductive paper method for the aim of checking and extending the theory. Experiments are done with several kinds of 1/5 and 1/10 magnified models. The results obtained by these experimental methods are nearly the same of the theoretical ones and therefore will not be reproduced here. Final studies are about partial discharge measurements. The equipment used in the experimental works and the measurement funda mentals are described. At 50 Hz AC and DC voltages, partial dis charge tests are performed to investigate. (1) The importance of measuring frequency, (2) The versus of the partial discharge inception voltage and discharge intensity with the radius of curvature of point electrode, (3) The effect of electrode spacing on the partial discharge (corona) inception voltage, (4) The effect of temperature on the partial discharge inception voltage, (5) The effect of pressure on the partial discharge inception voltage, (6) The RIV (Radio Interference Voltage) of corona discharge reference source, (7) The partial discharge repetition rate versus applied voltage and (8) The determination of breakdown voltage. The overall results may be summarized as follow: (1) The magnitude of partial discharges is mainly determined by the radius of curvature of the point. The partial discharge incep tion voltage also varies with the radius. The partial discharge quantities vary with the top angle of the point. The radius of the hemisphere does not substantially affect the discharge magnitude. (2) The experiments performed on the change, in magnitude with change in point-to-hemisphere distance show that over a 5 mm range, the discharge magnitude can be reduced by approximately 28 % at negative voltage and 20 % at 50 Hz AC without seriously affecting the stability of discharge pattern. Increase of the separation increases the discharge inception voltage but only by approxi mately 6 % at all cases over the range indicated, as this change is almost a linear function of separation. Here, the normal position of the point, i.e. where it coincides with the diametric plane of the hemisphere, has been taken as zero separation. (3) Under high direct voltage conditions, corona discharge reference source provides discharge pulses of constant magnitudes as in alternating voltage conditions, but the magnitudes vary with the polarity. The partial discharges appear sooner at negative than at positive voltage; with AC voltage they occur often during the negative half-cycle of sine wave only. (4) The discharge (corona) inception voltage with temperature reduce by approximately 10 % from the initial value for a 25-75 C temperature range. (5) The partial discharge inception voltage decrease considerably with pressure at low pressure range. Discharge inception volt age with pressure increase by approximately 75 % from the initial value for a 0-5 bar pressure range. (6) The partial discharge repetition rate is strongly dependent on the voltage. The repetition rate increases with applied voltage as in alternating voltage case. (7) The RIV (Radio Interference Voltage) level of corona discharge reference source is not of importance. (8) Corona discharge reference source can be used as an alternative calibration source under high direct voltage conditions. It is sufficiently reliable to be accepted as a secondary discharge standard. It is simple and of reasonable size, and a range of specific discharge magnitude can be obtained using only a small number of points. xx SEMBOLLER a b c C C a Cb D A Af E E o E max r f(n) f.. o Sivri uç elektrodun tepe açısı; iyonlaşma katsayısı Elektrot açıklığı; elips ve hiperbolde büyük eksen uzunluğu Elips ve hiperbolde küçük eksen uzunluğu Elips ve hiperbolde yarı odak uzaklığı Kapasite Deney cisminin kapasitesi Bağlama (kuplaj) kondansatörü Akı yoğunluğu Korona tabakasının kalınlığı Band genişliği Elektrik alan şiddeti Ortalama elektrik alan şiddeti Maksimum alan şiddeti Dielektrik sabiti -12 F/: m Boşluğun dielektrik sabiti = 8,86.10 Bağıl dielektrik sabiti Kısmi boşalma ölçü aletinin boşalma tekrarlama sıklığına bağlı bir fonksiyonu : Ölçme frekansı h, h, h : Genel metrik katsayılar u v w J h, h_, h, : Sf eroidal koordinat sisteminde metrik katsayılar n 8 (J> h, h, h, : Paraboloidal koordinat sisteminde metrik katsayılar -*??*?-*? i, iQ, i : Silindirik koordinat sisteminde birim vektörler r o z xıı } n n, RK q Q t T U Ud u u dA U. i U. ıa U. in U. IP Sferoidal koordinat sisteminde birim vektörler Paraboloidal koordinat sisteminde birim vektörler Akım yoğunluğu Düzeltme faktörü Öziletkenlik Anten uzaklığı Kısmi boşalma tekrarlama sıklığı Faydalanma faktörü Sferoidal koordinatlar Paraboloidal koordinatlar Basınç; geometrik karakteristik Sivri uçlu elektrodun eğrilik yarıçapı Yarıküre elektrodun yarıçapı; direnç Yarıçap değişkeni Silindirik koordinatlar Koruma direnci, ön direnç Boşalma genliği (pC); görünen yük Elektrik yükü Sıcaklık Zaman sabiti Gerilim Delinme gerilimi Korona tabakasının delinme gerilimi Kısmi boşalma sönme gerilimi Kısmi boşalma (korona) başlangıç gerilimi Alternatif kısmi boşalma (korona) başlangıç gerilimi Negatif kısmi boşalma (korona) başlangıç gerilimi Pozitif kısmi boşalma (korona) başlangıç gerilimi xııı U : Boşalma genliği (yV) ; radyo parazit gerilimi u, v, w : Genel koordinatlar x : Uzaklık değişkeni x, y, z : Kartezyen koordinatlar V : Potansiyel W : Enerji Z : Kısmi boşalma ölçü empedansı KISALTMALAR SYK : Sivri uç-yarıküre elektrot düzeni RKK. : Referans korona kaynağı AG : Alternatif gerilim DG : Doğru gerilim TS : Türk Standardları IEC : International Electrotechnical Commission BS : British Standards CISPR : Comite International Special des Perturbations Radioelectriques NEMA : National Electrical Manufacturers Association RIV : Radyo parazit gerilimi (Radio Interference Voltage) MWB : Messwandler - Bau GMBH HFM : MWB RIV-metresi ÖA : Ölçü aleti, RIV-metre, pC-metre KIO : Katot ışınlı osiloskop PVC : Polivinilklorür IEE. Institution of Electrical Engineers IEEE : Institute of Electrical and Electronics Engineers DoktoraPh.D

Determination of Voltage Level from Audible DC Corona Noise by Using Neural Network

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Data-Driven Approach for Estimating Power and Fuel Consumption of Ship:A Case of Container Vessel

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