Evaluation of Filtered Spark Gap on the Lightning Protection of Distribution Transformers: Experimental and Simulation Study

Protection of transformers, as one of the most expensive equipment in the power system, against lightning overvoltage impulses is a vital task. This paper, for the first time so far, investigates the effects of a filtered spark gap on the protection level of transformers against lightning overvoltage impulses. The filter is an inductor that is placed in series with the transformer and before the spark gap aiming to reduce the voltage at the connection point of the spark gap, and hence, enhancing the protection level of the transformer under lightning overvoltages. The experimental laboratory tests are accomplished on a 400 kVA, 22/0.4 kV, Delta-Star ( Δ − Y ) connection type transformer under 110 kV, and 125 kV overvoltage impulses, whereas the size of the spark gap is set to 80 mm and two inductors of 35 μ H and 119 μ H are considered. In order to perform a more in-depth analysis, a model that works reasonably close to the empirical case is developed in the EMTP-RV software. An optimization algorithm is used to determine the sensitive parameters of the double-exponential function, which is used to reproduce the applied laboratory lightning impulse voltages in the EMTP-RV environment. Moreover, the transformer is modeled according to the Cigre Guidelines (Working Group 02 of Study Committee 33). The behavior of the spark gap is simulated as close as the practical situation using the disruptive effect method. The preciseness of the simulated filtered spark gap model is verified by comparing the results of the simulated model in the EMTP-RV with the results of experimental tests. After verifying the model, different sizes of inductors are studied in the EMTP-RV environment to investigate whether larger or smaller inductors provide better protection for the transformer under lightning conditions. A comparison is performed among the conventional spark gap, surge arrester, and the filtered spark gap to provide a better analysis of the potential of the proposed device. The results indicate that proper sizing of the inductor, within an effective range, slightly enhances the protection level of the transformer.

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A Simple Mismatch Mitigating Partial Power Processing Converter for Solar PV Modules

Energies ◽

10.3390/en14082308 ◽

2021 ◽

Vol 14 (8) ◽

pp. 2308

Author(s):

Kamran Ali Khan Niazi ◽

Yongheng Yang ◽

Tamas Kerekes ◽

Dezso Sera

Keyword(s):

Experimental Tests ◽

Energy Yield ◽

Power Electronic ◽

Solar Pv ◽

Partial Shading ◽

Loss Analysis ◽

Pv Systems ◽

Pv Module ◽

Pv Modules ◽

In Series

Partial shading affects the energy harvested from photovoltaic (PV) modules, leading to a mismatch in PV systems and causing energy losses. For this purpose, differential power processing (DPP) converters are the emerging power electronic-based topologies used to address the mismatch issues. Normally, PV modules are connected in series and DPP converters are used to extract the power from these PV modules by only processing the fraction of power called mismatched power. In this work, a switched-capacitor-inductor (SCL)-based DPP converter is presented, which mitigates the non-ideal conditions in solar PV systems. A proposed SCL-based DPP technique utilizes a simple control strategy to extract the maximum power from the partially shaded PV modules by only processing a fraction of the power. Furthermore, an operational principle and loss analysis for the proposed converter is presented. The proposed topology is examined and compared with the traditional bypass diode technique through simulations and experimental tests. The efficiency of the proposed DPP is validated by the experiment and simulation. The results demonstrate the performance in terms of higher energy yield without bypassing the low-producing PV module by using a simple control. The results indicate that achieved efficiency is higher than 98% under severe mismatch (higher than 50%).

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IV. On the nature of the streamers in the electric spark

Philosophical Transactions of the Royal Society of London. Series A, Containing Papers of a Mathematical or Physical Character ◽

10.1098/rsta.1909.0004 ◽

1909 ◽

Vol 209 (441-458) ◽

pp. 71-87 ◽

Cited By ~ 11

Keyword(s):

Incident Light ◽

Close Relation ◽

Actual Process ◽

Metal Vapour ◽

New Era ◽

Spark Gap ◽

In Series ◽

The Subject ◽

The Doppler Effect ◽

The Individual

When the oscillating electric spark is examined in a rapidly rotating mirror, the successive oscillations render themselves evident in the image as a series of lumnious curved streamers which emanate from the poles and extend towards the centre of the spark gap. These streamers were first observed by Feddersen in 1862, but the work of Schuster and Hemsalech in 1900 may be said to have opened up a new era in the subject. These workers threw the image of the spark on the slit of a spectroscope, and photographed the resulting spectrum on a film which was maintained in rapid rotation in a direction at right angles to that of the incident light. In their photographs they found that the air lines extended straight across from pole to pole, but that the metal lines were represented by curved bands drawn out in the centre of the spark gap. There is a close relation between these bands and the streamers seen in the unanalysed inductive spark. Schuster and Hemsalech carried out their experiments with the smallest possible inductance in series with the spark, and thus made the period of the oscillations so small that the drawing out on the film was insufficient to separate the individual oscillations from each other. Thus their curved lines represent a composite structure, consisting of all the streamers due to the successive oscillations superposed on each other. It follows from their results that the light of the streamers in the spark is entirely produced by the glowing of the metallic vapour of the electrodes, and that, while the luminosity of the air is practically instantaneous in its occurrence, that due to the metal vapour occurs in the centre of the spark gap an appreciable time later than near the poles. The actual process which goes on in the spark and gives rise to this delay in the arrival of the metallic vapour at the centre of the gap is not yet thoroughly understood. Schuster and Hemsalech make the natural supposition that it is due to the fact that the metal of the electrode is vaporised and rendered incandescent by the heat of the spark, and that the vapour takes an appreciable time to diffuse from the electrodes to the centre of the gap. The exception which has been taken to this view has arisen in part from the difficulty of observing the Doppler effect on the metallic lines which should be a concomitant of the diffusion of the vapour from the poles, and in part from the extraordinary results which the authors themselves obtained in some metals for the velocity of the diffusion corresponding to the different lines. In the case of bismuth and, in a less degree, of cadmium the different metallic lines could be divided into groups of different curvatures which indicated different velocities of diffusion towards the centre of the gap. As regards the former matter, there does not seem to be involved any real difficulty to the explanation, as Dr. Schuster has himself recently shown. The curious effect of the different curvatures of the lines of the same element has, however, always remained more or less of a difficulty in the way of a complete acceptance of their view. Schuster and Hemsalech themselves refer to the possibility in the case of bismuth that the metal may be a compound, and that the two kinds of molecules give rise to the differently curved lines. Other explanations have been made by different writers, but it cannot be said that any explanation adequately supported by experiment has been forthcoming. In view of this incompleteness in our knowledge of the constitution of the streamers it seemed to me that further observations with a rotating mirror would possibly be of value, and the investigations recorded below succeed, I think, in throwing a clearer light on the nature of the streamers, and on certain other phenomena which are characteristic of the spark.

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Sheet Hemming with Rolling Tools: Analysis and Optimization of the Part Quality

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.344.357 ◽

2007 ◽

Vol 344 ◽

pp. 357-364 ◽

Cited By ~ 4

Author(s):

Elisabetta Ceretti ◽

Aldo Attanasio ◽

Antonio Fiorentino ◽

Claudio Giardini

Keyword(s):

Tool Path ◽

Outer Part ◽

Experimental Tests ◽

Process Time ◽

Cnc Machine ◽

Whole Process ◽

Cad Cam ◽

In Series ◽

Aluminium Sheets ◽

Set Up

The present paper is the continuation of a research conducted on hemming operations by using rolling tools. Sheet hemming is a joining operation widely used in automotive industry when it is necessary to join two sheet parts (such as the engine hood or the door panels with their internal frame) by plastic deformation of the edge of the outer part. The whole process is characterised by a 90° sheet flanging, a pre-hemming (up to approximately 135°) and the final hemming where the outer sheet edge is bended up to 180° clamping the inner sheet. Hemming processes are normally performed using rigid dies in series production and manually in pre-series and small batch production, due to the high cost of the dies. Nowadays, rollers moved by robots are becoming an interesting alternative to the manual operations especially when flexible productions are required. Even if the process time is higher, this solution can help in minimizing set-up times and costs. The required equipments are a support and a blocking system for the sheets together with the rollers mounted on a CNC machine or on a robot. The production flexibility is guaranteed by changing the 3D tool path using a CAD/CAM system. Authors are dealing with this technique having conducted many experiments studying the influence of the hemming process parameters such as flange geometry (edge height, fillet radius), distance of the inner panel from the flange, tool path sequence, along straight paths on steel sheets. The goal of the present research is to study the material behaviour and the produced parts quality when working on aluminium sheets. In particular, both experimental tests and simulations will be carried out in order to optimize the process.

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The fine-structure of some lines in the visible region of the spectrum of thallium III

Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character ◽

10.1098/rspa.1930.0142 ◽

1930 ◽

Vol 129 (809) ◽

pp. 43-47 ◽

Cited By ~ 8

Keyword(s):

Fine Structure ◽

Visible Region ◽

Nuclear Moment ◽

Nichrome Wire ◽

Spark Gap ◽

High Tension ◽

In Series ◽

The One ◽

Theoretical Results ◽

Line Classification

From a study of the fine-structure of some lines in the arc spectrum of thallium Schüler and Brück concluded that the nucleus of the thallium atom possessed a moment of momentum given by ½ h /2π and this value was confirmed by work on the first spark spectrum of the element. The value of the nuclear moment being known the structure of the lines in the second spark spectrum could be predicted and the present paper is the account of an investigation of a number of these lines which lie in the visible region, a comparison being drawn between the experimental and the theoretical results. The source of light used was similar to the one employed by McLennan, McLay and Crawford in the excitation of the first and second spark spectra of thallium for the purpose of line classification. It consisted of a quartz tube about 50 cm. long and 1½ cm. in diameter with a plain window in each end and provided with aluminium electrodes sealed into side tubes. The metal whose spectrum was to be studied was scattered along thé bottom of the tube and the tube evacuated. The metal was then vaporised by hear supplied by a coil of nichrome wire wound on the tube. This coil must be wound non-inductively or the desired excitation will not be obtained. The high tension across the terminals was produced by joining them in series with the secondary of a 30,000-volt transformer and a spark gap of about 1 c. m., a condenser being connected in parallel.

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The Behaviour of Mistuned Piezoelectric Shunt Systems and Its Estimation

Shock and Vibration ◽

10.1155/2016/9739217 ◽

2016 ◽

Vol 2016 ◽

pp. 1-18 ◽

Cited By ~ 6

Author(s):

M. Berardengo ◽

S. Manzoni ◽

M. Vanali

Keyword(s):

Experimental Tests ◽

Vibration Damping ◽

Piezoelectric Transducers ◽

Electric Impedance ◽

Rapid Prediction ◽

Vibration Attenuation ◽

In Series ◽

Dynamical Features ◽

Impedance Parameters ◽

Piezoelectric Shunt

This paper addresses monoharmonic vibration attenuation using piezoelectric transducers shunted with electric impedances consisting of a resistance and an inductance in series. This type of vibration attenuation has several advantages but suffers from problems related to possible mistuning. In fact, when either the mechanical system to be controlled or the shunt electric impedance undergoes a change in their dynamical features, the attenuation performance decreases significantly. This paper describes the influence of biases in the electric impedance parameters on the attenuation provided by the shunt and proposes an approximated model for a rapid prediction of the vibration damping performance in mistuned situations. The analytical and numerical results achieved within the paper are validated using experimental tests on two different test structures.

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On the excitation of the band spectrum of helium

Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character ◽

10.1098/rspa.1925.0122 ◽

1925 ◽

Vol 109 (750) ◽

pp. 267-272 ◽

Cited By ~ 4

Keyword(s):

Discharge Tube ◽

High Current Density ◽

Band Spectrum ◽

Essential Condition ◽

Spark Gap ◽

In Series ◽

Pure Helium ◽

Faint Band ◽

The Individual ◽

Low Pressures

It is now generally agreed that the band spectrum of helium, which was first observed by Curtis (‘Roy. Soc. Proc.,’ A, vol. 89, p. 146, 1913) and by Goldstein (‘Verh. d. Deutsch. Phys. Gesell.,’ vol. 15, p. 402, 1913), is to be attributed to some molecule of helium. This band spectrum is peculiar in the fact that the heads of the bands have been shown by Fowler (‘Rov. Soc. Proc.,’ A, vol. 91, p. 208, 1915) to follow the law usually associated with line spectra, though the individual lines composing the bands can be represented by the parabolic arrangement appropriate to band series. More recently, Curtis has carried out a series of investigations (‘Roy. Soc. Proc.’) on the structure of the bands in terms of the quantum theory. Attention may here be drawn to two peculiarities in the spectrum. There is one isolated band with a head at about λ = 5733 A., which is degraded to the violet, whilst all the remaining bands are degraded to the red. Also Goldstein ( loc. cit. ) observed a number of faint band lines in the region about λ = 5390 A. to λ = 5270 A., which were not recorded in Curtis’s paper ( loc. cit .). It is well known that in vacuum tubes excited by uncondensed discharges only faint traces of the principal band heads are visible in the positive column though the complete band spectrum appears in the negative glow. The band spectrum can be excited with much greater intrinsic brightness by using a discharge tube with a wide tube in place of the usual capillary, and exciting it by means of a discharge from an induction coil or transformer, with a condenser in parallel and a small spark gap in series with the discharge tube, the band spectrum under these conditions appearing throughout the tube. There appears to be an optimum length of spark gap and the spectrum tends to become weaker when the length is increased beyond a certain point. Curtis ( loc. cit .) has found that the band spectrum is not strongly developed at low pressures, and this condition appears to be independent of other conditions of excitation. In the present investigation we have found that under certain conditions the band spectrum can be greatly modified. It was observed that when a vacuum tube, containing pure helium, which had been made with the capillary in several sections of different bore, was excited with an uncondensed discharge the narrowest section, which was of the finest thermometer tubing that could be worked conveniently in the blowpipe, showed nothing but the line spectrum, but in the wider sections on either side the band spectrum was quite strongly developed. This seems to show that a high-current density is not an essential condition for the excitation of the band spectrum, but it was remarkable that with these tubes it appeared in the wider parts, where it would not have been seen if the capillaries had not been provided with a section of narrow bore.

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Failures’ Diagnosis of High Voltage Power Supply System for Low Power Magnetrons

International Journal of Advanced Trends in Computer Science and Engineering ◽

10.30534/ijatcse/2021/421012021 ◽

2021 ◽

Vol 10 (1) ◽

pp. 295-300

Keyword(s):

High Voltage ◽

Power Supply ◽

Basic Element ◽

High Voltage Power Supply ◽

Voltage Variation ◽

Three Phase ◽

Voltage Doubler ◽

In Series ◽

Experimental Laboratory ◽

Transformer Core

This paper treats the study of the equivalent magnetic flux leakage transformer core type; it uses three-phase high voltage power supplies for a magnetron in each phase. This special transformer feeds a voltage doubler, a current stabilizer cell in series per phase. It ensures the anodic current stabilization in each magnetron by saturation of its magnetic circuit. It has additional leakage flux, which protects the magnetron against any eventual voltage variation; it is considered the basic element of this power supply.The simulation results with MATLAB-Simulink environment of the electrical operation of this power supply device were consistent with the experimental laboratory tests in the case of single-phase high voltage for one magnetron. This results obtained shows the feasibility of the proposed simulation model

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Transient impedance of grounding system with impulse superimposed sinewave

ENP Engineering Science Journal ◽

10.53907/enpesj.v1i1.7 ◽

2021 ◽

Vol 1 (1) ◽

pp. 8-12

Author(s):

Sherif Ghoneim ◽

Ahdab Elmorshedy ◽

Rabah Amer

Keyword(s):

System Configuration ◽

System Operation ◽

Grounding System ◽

Several Variables ◽

Wire Conductor ◽

Lightning Impulse ◽

In Series ◽

Grid Side ◽

Soil Ionization ◽

Impulse Current

Investigating the transient performance of grounding systems subject to lightning (impulse or impulse superimposed sinewave) is valuable for protecting the power system and maintaining the system operation. In this work, the grounding system's impedance is computed when an impulse superimposed sinewave is applied to the grounding grid's proposed lumped circuit and grounding system can be simulated as an inductance in series with resistance, and all of them are in parallel with capacitance based on Thione's assumption. Several variables were investigated to study their effects on the grounding system's behavior. The variables were the soil resistivity, soil permittivity, main wire length, grid conductor radius, grid side length, grid configurationand its mesh number. The grounding system configuration varied between square and rectangular shapes, which connects to the protecting rod via the main wire conductor. A 3.69 kA peak of impulse current was applied to avoid soil ionization. The results indicated the performance of the grounding system when subjecting to impulse current.

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An Intelligent Electronic Fuse (iFuse) to Enable Short-Circuit Fault-Tolerant Operation of Power Electronic Converters

10.36227/techrxiv.13030748.v1 ◽

2020 ◽

Author(s):

Alber Filba-Martinez ◽

Salvador Alepuz ◽

Sergio Busquets-Monge ◽

Adria Luque ◽

Josep Bordonau

Keyword(s):

Fault Tolerant ◽

Short Circuit ◽

Failure Detection ◽

Experimental Tests ◽

Power Electronic Converters ◽

Novel Device ◽

Current Path ◽

In Series ◽

Short Circuit Fault ◽

Short Circuit Currents

The present paper proposes a novel device defined as an intelligent electronic fuse (iFuse) meant to be connected in series with any current-bidirectional voltage-unidirectional active switch present in a given converter. The iFuse duty is to isolate its series- associated switch from the rest of the converter circuit immediately after detecting that said switch has failed in short circuit. Nonetheless, it maintains the reverse (free- wheeling) current path originally offered by the failed switch. The failure detection is performed when the failed switch causes a shoot-through event. Therefore, the iFuse is designed to be able to block the elevated current occurring in such event. The iFuse allows increasing the fault-tolerant capability and the reliability of power converters where such qualities are hindered by switch short-circuit failures, as in converters featuring parallelized switches, neutral-point-clamped multilevel topologies, or redundant legs. The feasibility of the iFuse device is verified through experimental tests, proving that the device is able to detect the failure of its associated switch and isolate it from the rest of the converter circuit in 6 μs, while stopping short-circuit currents of up to 1 kA without incurring in harmful di/dt values.

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