High Voltage Electrical Apparatus Research Articles

Graphical examination of dissolved gas analysis by ratio methods and Duval triangle method to investigate internal faults of power transformer

Power transformer is a pivotal high voltage electrical apparatus of power system network. It is robust, bulky and one of the costliest equipment’s among all other connected network elements. Dissolved gas analysis (DGA) is one of the most popular proven methods to detect internal faults of power transformer. This research article incorporates ratio based DGA method using fuzzy logic as well as Duval Triangle based DGA method to analyse the internal faults of power transformers. Comparison of two distinct methods of DGA analysis for prevention of catastrophic failure is presented. The industry based standard data set are used for analysis and validation.

Global Temperature Sensing for an Operating Power Transformer Based on Raman Scattering.

Traditional monitoring methods cannot obtain the overall thermal information for power transformers. To solve this problem, a distributed fiber optic sensor (DFOS) was creatively applied inside an operating 35 kV power transformer by highly integrating with the electromagnetic wires. Then, the transformer prototype with totally global sensing capability was successfully developed and it was qualified for power grid application through the strict ex-factory tests. The as designed optical fiber sensor works stably all the time with a temperature accuracy of ±0.2 °C and spatial positioning accuracy of 0.8 m. Based on the obtained internal temperature distribution, Gaussian convolution was further applied for the signal processing and hereby, the hotspots for all the windings and iron cores could be accurately traced. The hottest points were located at 89.1% (55 °C) of the high voltage winding height and 89.7% (77.5 °C) of the low voltage winding height. The actual precise hotspot location corrected the traditional cognition on the transformer windings and it would serve as an essential reference for the manufactures. This new nondestructive internal sensing and condition monitoring method also exhibits a promising future for the DFOS applying in the high-voltage electrical apparatus industry.

Study on the Main Inner Insulation of 1100kV UHVAC Oil-gas Bushing and the Structure Optimization Design of its Fittings

The oil-gas bushing has the characteristics of compact structure and small floor area, which can be widely used in various voltage level substations to realize the electrical connection between transformer and high-voltage combined electrical apparatus GIS. At present, the development of oil-gas bushing for 1100kV AC extra high voltage level is the first time. It is necessary to solve the problems of the material development of main insulation core of bushing, the design and optimization of main insulation of core and the current carrying capacity of large current conductor of bushing structural design and other key technologies. This paper focuses on the analysis and calculation of the optimization design of main insulation structure of 1100kV UHV oil-gas bushing. Considering that the end of the oil-gas bushing is connected to the winding side of the transformer and the center conductor of the high-voltage combined electrical appliance in the narrow space, it is necessary to optimize the design of the structure of the fittings at both ends of the bushing to ensure that the electric field distribution is reasonable under the action of high voltage, and that it carries large current without local overheating area. Based on this, three-dimensional finite element simulation model of UHV oil-gas bushing tooling is established, and the main insulation structure of the bushing core is optimized to make its axial and radial field strength meet the control requirements. The topological structure and size of the current carrying structure in the center of the bushing and the voltage equalizing device at both ends are given, and the prototype and supporting tooling structure of the oil-gas casing are developed according to the optimized design structure, and go through various bushing type tests. In this paper, the optimized design and development of the main insulation structure of UHV oil-gas bushing, taking into account processing and installation of transformer outgoing line structure and the GIS electrical connection supporting tooling of the high-voltage combined apparatus, simulating the actual operation environment of the UHV oil-gas bushing with full voltage and full current, and carrying out the long-term performance evaluation test, has good engineering application guidance value.

Wavelet Kernel based Convolutional Neural Network for Localization of Partial Discharge Sources within a Power Apparatus

This article presents a new convolutional neural network (CNN) topology using wavelet kernels to detect and discriminate single or multiple partial discharge (PD) locations in high voltage power apparatus with increased accuracy. The method is tested on an electrical equipment model with acoustic PD sensors. A cubical tank has been emulated in the laboratory representing the equipment under test and partial discharge sources have been placed at different positions along with the required data acquisition hardware. The present scheme eliminates the requirement of separate algorithms for feature extraction and classification of the acquired PD signals. Wavelet kernels of the CNN play a crucial role in feature learning, and the proposed CNN architecture as a whole, can classify the features in a supervised manner. The performance of the proposed scheme is compared with other existing methods using the same data set . It is found that an overall accuracy of 97.64% is achieved by the proposed method, outperforming other existing methods by a significant margin of at least 5% in terms of accuracy. The developed module is a generic one and can be adapted for different high voltage electrical apparatus with similar topological structures; hence, it can be used in various ways in power industry.

A Denoising Algorithm for Partial Discharge Measurement Based on the Combination of Wavelet Threshold and Total Variation Theory

In electrical engineering, partial discharge (PD) measurement is frequently employed to detect insulation defects and judge insulation conditions of high-voltage electrical apparatus. However, it is easily corrupted by white noises in the field. In this article, a joint algorithm is proposed, in which the wavelet threshold and total variation (TV) denoising methods are combined by the convex optimization theory to denoise ultrahigh frequency (UHF) PD signals corrupted by white noises. Since the two respective methods are incorporated into the joint algorithm, it is with high potential to reduce oscillation error introduced by the wavelet threshold method and eliminate stair error introduced by the TV denoising method. In order to validate the effect of the proposed algorithm, a numerical simulation is carried out to compare it with several existing methods. Indicators of their performance are computed, and the results verify that the proposed algorithm outperforms all the other methods.

The Comprehensive Management System of High Voltage Electrical Test Apparatus

High-voltage test is critical to electrical equipments, and test apparatus used in high-voltage test and their test items are various and complex. In the paper we focus on the standardized management of test apparatus. Adapting to information-data-intelligent tendency, we construct a comprehensive management system for high-voltage electrical test apparatus to improve test accuracy and efficiency. We use two-dimensional bar code to build transceiver system. Through simple scanning, the instruments could easily change their status and location, and we can also get all its data stored in the database. The online report generation are achieved as well based embedded template, bookmark and electronic signature. The trial operation shows that our detection processing time reduces more than 33 percents, which increases detection accuracy and reliability.

Improvement of thermal conductivities for PPS dielectric nanocomposites via incorporating NH2-POSS functionalized nBN fillers

The proposed combining method of silane coupling agent of γ-aminopropyl triethoxy silane/aminopropyllsobutyl polyhedral oligomeric silsesquioxane (KH-560/NH2-POSS) was performed to functionalize the surface of hexagonal nanometer boron nitride fillers (f-nBN), aiming to fabricate the f-nBN/polyphenylene sulfide (f-nBN/PPS) nanocomposites with excellent thermal conductivities, outstanding thermal stabilities and optimal dielectric properties. The usage of f-nBN fillers was benifit for improving the thermally conductive coefficient (λ) and decreasing dielectric constant (ε) values of the PPS nanocomposites. The f-nBN/PPS nanocomposite with 60wt% f-BN fillers was an excellent dielectric nanocomposite with high λ & ideal ε values and outstanding thermal stability, λ of 1.122W/mK (increased by 400% compared to that of pristine PPS matrix), ε of 3.99 and THeat-resistance index (THRI) beyond 275°C, which holds potential for electronic packaging materials and ultra high voltage electrical apparatus.

Chemical and Electron Interaction Properties of Potential Gaseous Insulation and Arc-quenching Media

The global warming effects of sulphur hexafluoride (SF<sub>6</sub>) lead researchers to look for new environmentally-friendly gas media in high-voltage electrical apparatus. The present paper discusses basic chemical and electron interaction properties that brings high insulation strength and good arc interruption capability for a gas. The conclusion shows that gaseous compounds composed of elements in the upright area of periodic table of elements generally have stronger electronegative ability and good electrical properties. And double bond or triple bond in gas molecule can effectively improve the dielectric strength. For gas mixtures, good cooperation of gases will generate synergetic effect, which makes its dielectric strength higher than the weighted average value of each gas. Some aspects in searching for new arc interruption media are also discussed.

Investigation on Equipment Failure Mode and Causes Using Infra-Red Thermovision Camera Images for High Voltage Electrical Connection

High voltage (HV) electrical connection hot spot scanning and monitoring is important to ensure the availability, continuity and reliability of electrical supply. The aim of this research work is to investigate HV electrical connection apparatus using infra-red thermovision camera. A database of hot spot images from infra-red thermovision scanning is needed to perform an analysis to ascertain the mode and causes of the hot spot. Eight numbers of Tenaga NasionalBerhad’s (TNB) main intakes (PMU) with different location, environment type, and load were selected to get various data to be formed a hot spot database. The database consist of HV electrical apparatus scanning image using infra-red thermovision camera to investigate the hot spot temperature reading, location and bay in dedicated PMU. The data collected from year 2010 until 2013 were analyzed to ascertain the failure modes of the HV electrical connection apparatus according to TNB condition monitoring unit standards. All objectives were achieved by performing the database, equipment failure mode and causes were ascertained are related to the load (MW) and bad workmanship during erection process. Connection apparatus with high hot spot reading were investigated, repaired or taken out from services if damage, and replaced. Solutions were proposed on the damage electrical HV electrical connection apparatus depends on the source of the problem.

Application of Back Propagation Neural Network for Partial Discharge Pattern Recognition

This paper proposes a pattern recognition approach based on the back propagation (BP) neural network for identifying insulation defects of high-voltage electrical apparatus arising from partial discharge (PD). Pattern recognition of PD is used for identifying defects causing the PD, such as internal discharge, external discharge, corona, etc. This information is vital for estimating the harmfulness of the discharge in the insulation. Since an insulation defect, such as one resulting from PD, would have a corresponding particular pattern, pattern recognition of PD is significant means to discriminate insulation conditions of high-voltage electrical apparatus. To verify the proposed approach, experiments were conducted to demonstrate the field-test PD pattern recognition of model insulators with artificial defects are purposely created to produce the common PD activities of insulators by using feature vectors of field-test PD patterns. The experimental data are found to be in close agreement with the recognized data. The experimental results show that the proposed approach is very effective for recognizing the defects of high-voltage electrical apparatus.

Partial Discharge Pattern Recognition of Cast Resin Current Transformers Using Radial Basis Function Neural Network

This paper proposes a novel pattern recognition approach based on the radial basis function (RBF) neural network for identifying insulation defects of high-voltage electrical apparatus arising from partial discharge (PD). Pattern recognition of PD is used for identifying defects causing the PD, such as internal discharge, external discharge, corona, etc. This information is vital for estimating the harmfulness of the discharge in the insulation. Since an insulation defect, such as one resulting from PD, would have a corresponding particular pattern, pattern recognition of PD is significant means to discriminate insulation conditions of high-voltage electrical apparatus. To verify the proposed approach, experiments were conducted to demonstrate the field-test PD pattern recognition of cast resin current transformer (CRCT) models. These tests used artificial defects created in order to produce the common PD activities of CRCTs by using feature vectors of field-test PD patterns. The significant features are extracted by using nonlinear principal component analysis (NLPCA) method. The experimental data are found to be in close agreement with the recognized data. The test results show that the proposed approach is efficient and reliable.

친환경 고압배전반 개발을 위한 dry air의 압력별 절연내력특성 분석에 관한 연구

The environmental pollution caused by green-house gases such as CO₂ and SF6 has been becoming the main issue of industrial society. Many developed countries are making efforts to minimize the amount of CO₂ emission come from the operation of high voltage electrical apparatuses. As a part of these efforts, 180 countries signed the Kyoto Protocol in 1997 to cut back on their green-house gas emissions. Nowadays, the study on the development of dry air insulated switchgear (DAIS) which is known as an eco-friendly electrical apparatus is in progress. A DAIS is advantageous for minimizing the effect of impurities and enhancing the dielectric characteristics over an air insulated switchgear (AIS) by applying constant pressure to an enclosed cubicle. Therefore, a study on the electrical insulation performance of dry air as a gaseous insulation medium is conducted in this paper to substitute a gas insulated switchgear (GIS) for DAIS. As results, it is verified that the AC dielectric characteristics of dry air are similar to those of air and the lightning impulse dielectric characteristics of dry air are superior to those of air at 1bar pressure condition. However, dry air is of inferior dielectric characteristics to SF6 at 4bar pressure condition. Finally, it is suggested that the internal pressure of DAIS should be over 4bar pressure to develop a high voltage switchgear which has similar electrical performance to a conventional GIS. Also, the empirical formulae on calculating the maximum electric field intensity at sparkover of dry air are deduced by experiments according to pressures. It is expected that these results are helpful to design and develop a high voltage electrical apparatus.

방사전자파를 이용한 고분자애자의 오손량 분류기법

Recently, diagnosis techniques have been investigated to detect a Partial Discharge associated with a dielectric material defect in a high voltage electrical apparatus, However, the properties of detection technique of Partial Discharge aren't completely understood because the physical process of Partial Discharge. Therefore, this paper analyzes the process on surface discharge of polymer insulator using wavelet transform. Wavelet transform provides a direct quantitative measure of spectral content in the time~frequency domain. As it is important to develop a non-contact method for detecting the kaolin contamination degree, this research analyzes the electromagnetic waves emitted from Partial Discharge using wavelet transform. This result experimentally shows the process of Partial Discharge as a two-dimensional distribution in the time-frequency domain. Feature extraction parameter namely, maximum and average of wavelet coefficients values, wavelet coefficients value at the point of <TEX>$95\%$</TEX> in a histogram and number of maximum wavelet coefficient have used electromagnetic wave signals as input signals in the preprocessing process of neural networks in order to identify kaolin contamination rates. As result, root sum square error was produced by the test with a learning of neural networks obtained 0.00828.

Detection of wide-band E-M signals emitted from partial discharge occurring in GIS using wavelet transform

Recently, diagnostic techniques have been investigated to detect a partial discharge (PD) associated with a dielectric material defect in a high-voltage electrical apparatus. Gas insulated switchgear (GIS) is an important equipment in a substation, it is highly desirable to measure a partial discharge (PD) occurring in GIS which is a symptom of an insulation breakdown. As it is important to develop a noncontact method for detecting the insulation fault, this paper proposes a new method to detect the wide-band electromagnetic (E-M) wave emitted from PD using the Wavelet transform. The Wavelet transform provides a direct quantitative measure of spectral content, "dynamic spectrum", in the time-frequency domain. This paper experimentally shows the "dynamic spectrum" of the wide-band E-M wave emitted from PD in the time-frequency domain. This method is shown to be useful for detecting the symptom of the insulation breakdown occurring in GIS.

SF&lt;sub&gt;6&lt;/sub&gt;ガス中における部分放電現象のウェーブレット変換を用いた時間周波数解析

Recently, diagnostic techniques have been investigated to detect a partial discharge (PD) associated with a dielectric material defect in a high-voltage electrical apparatus. However, the properties of PD aren't completely understood because the physical process of PD is complicated. For improvement of detection techniques of PD, it is important to make clear the fundamental physical process of PD. Therefore, this paper analyzes the process of PD using Wavelet transform. Wavelet transform provides a direct quantitative measure of spectral content ( Dynamic spectrum ) in the time-frequency domain. As it is important to develop a non-contact method for detecting the insulation fault, this paper analyzes the electromagnetic waves emitted from PD using Wavelet transform. This paper experimentally shows the process of PD as a two-dimensional distribution “Dynamic spectrum” in the time-frequency domain. This method is shown to be useful for detecting prediction of insulation fault.

ANAESTHESIA FOR THE IRRADIATED PIG: A STUDY IN REMOTE CONTROL

As a preliminary investigation of the comparative effects of the neutron beam from a 45-in. cyclotron with x rays from an 8-Mev linear accelerator, an anesthetic technique that would assure complete immobilization of the animals for several hours was sought. Choice of anesthetic technique was influenced by the nature of the experimental animal, and by the need for a nonexplosive agent (because of the proximity of high voltage electrical apparatus) which would provide safe anesthesia for long periods by remote control. For premedication, phenothiazine derivatives were chosen because they produce sedation without undue respiratory depression and because their effects are long lasting. Promazine (2 mg) and promethazine (1 mg per lb (0.45 kg) body weight) were given together by intramuscular injection 11/2 hours before induction of anesthesia. Parasympathetic depression was obtained with atropine sulfate (0.32 mg given by intramuscular injection after induction). Anesthesia was induced with intravenous thiopentone (250 mg for a 50-lb pig). On some occasions, to reduce the number of venepunctures, anesthesia was induced with cyclopropane. Pig and anesthetic apparatus were conveyed into the linear accelerator chamber, where the animal was irradiated with 8-Mev x rays. The whole process of anesthesia, transfer, positioning and irradiation took 5 tomore » 6 hr, and during much of this time the animal was inaccessible to the operating team. An optimal level of anesthesia was maintained by observing a stethograph which recorded the pig's respiratory changes. Rises in body temperature during irradiation were noted in some instances, and this was subsequently avoided by reducing ambient temperature and humidity.« less

Factors Influencing the Mechanical Strength of Cellulose Insulation

CELLULOSE insulation, like mineral oil with which it is usually associated in high-voltage electrical apparatus, is subject to deterioration in an increasing degree as the temperature of exposure is raised. This deterioration is a manifestation of the chemical instability of the cellulose. For a proper understanding of this change, it must be recognized that the fundamental chemical reactions involved are of two types. There are those changes which result from the oxidation of the cellulose and those which arise from the decomposition of its molecule. These changes are invariably intermingled in the normal commercial use of cellulose dielectric materials. To prevent dangerous deterioration and to secure the maximum service life of cellulose insulation, the effect produced by each type of reaction, the probability of its occurrence, and the means for its control must be carefully evaluated. Summary 1. Cellulose insulation will deteriorate in mechanical strength at a rate which increases with the increasing temperature of exposure. Deterioration will occur in the absence of an oxidizing atmosphere. 2. The rate of cellulose deterioration at a fixed temperature varies as the heat treatment is continued. 3. The mechanical deterioration of cellulose insulation at elevated temperature is the result of oxidation and pyrochemical decomposition. 4. When heated, cellulose passes through a “stable period” during which the mechanical properties are maintained. The presence of oxygen is chiefly effective in reducing the duration of this “stable period.” 5. The single effect of oxidation is restricted to the initial periods of treatment at temperatures lower than approximately 120 degrees centigrade. At higher temperatures, pyrochemical decomposition occurs. Even in the most favored temperature range, the effect of cellulose oxidation merges into the effects produced by pyrochemical decomposition as the deterioration progresses. 6. Heated under conditions which favor oxidation or pyrochemical change, the un-impregnated cellulose insulation deteriorates more rapidly than the same insulation after oil treatment and immersion. 7. The effect of oxidation is accelerated when pure oxygen gas is in contact with the insulation. No substantial difference in the rate of mechanical deterioration is observed when the oil-treat ed and oil-immersed insulation is aged in contact with nitrogen gas as compared to aging in contact with air.

The Measurement of High-Surge Voltages

With the application of surge tests to high voltage electrical apparatus, the question of the measurement of high-surge voltages has become a subject of prime importance. It is accordingly desired in Part I to show the practical work done in the laboratory at Sharon to calibrate the measuring devices, and in Part II to study the more interesting fundamental relationships that affect the operation and accuracy of these measuring devices. The methods of voltage measurement used are the resistance potentiometer, capacity potentiometer, and sphere gap. The potentiometers serve as dividers of the high-surge voltages for measurement at the cathode-ray oscillograph. The resistance potentiometer is a fundamental standard but requires consideration of its limitations for very rapid phenomena. In cases where these can be compensated for or are negligible, the resistance potentiometer method is very desirable. The capacity potentiometer is a secondary standard which can be calibrated. If corona and oscillations can be eliminated, it is a very desirable method of measurement, inasmuch as it is less subject to distorting the wave shape of the surge. The sphere gap is useful as a secondary standard for occasional check measurements, and it is of interest that formulas derived from smaller gaps still hold, as indicated by the check between the calculated curve for the 200-cm sphere gap and the calibration points with the resistance potentiometer.