Impulse Voltage Research Articles

Prediktivna kontrola adaptivnog modela za sistem magnetnog vešanja pod disperzijama početne pozicije i poremećajima napona

A nonlinear magnetic suspension system consisting of a mechanical motion and electromagnetic circuit is considered in this paper. An online algorithm that is used to stabilize the suspended mass targeting the desired ball position, ball velocity and coil current is presented. A steady-state condition, in which the ball position, the ball velocity, and the coil current were assumed constant, was used as a reference trajectory for the closed-loop simulations. An adaptive model predictive control method was employed to control the coil voltage while the discrete plant model and operating conditions were changed at each time step. The effectiveness of the proposed control law was validated in the presence of disturbances in initial ball position, steady-state ball position, suspended mass, and voltage using the Monte-Carlo simulation method. The sinusoidal, step, and impulse voltage disturbances were applied consequently to the system while imposing random dispersions of the initial ball position. Numerical results with five hundred trials illustrated that the designed algorithm can stabilize the system and track the desired reference without exceeding the state and input constraints despite the wide range of dispersions in initial ball position, steady-state ball position, suspended mass, and input voltage disturbances.

RANCANG BANGUN ALAT PASTEURISASI NON THERMAL DENGAN PULSED ELECTRIC FIELD (PEF)

ABSTRACTPackaged beverages have become a product that is very much on the market both internationally and nationally. In the process of making packaged beverages, in order to last longer the microbes in the drink must first be inactivated in order for the drink to last longer, the microbial inactivation process in the drink is called pasteurization. Convernsional pasteurization is done by heating the drink to be in production. But the high temperature of the drink can change the taste, color, and even nutrition of the drink. This is underpinning the non-thermal pasteurization process by using high voltage impulses (Pulsed Electric Field,PEF). PEF is a technology that utilizes high voltage DC to produce a field between two electrodes. Pateurization occurs when between electrodes there is milk that is flowed with high voltage DC. High voltage generation is performed using flyback transformers with voltage output up to 30 kV. In the pasteurization process given 6 voltage variations namely 5, 10, 12,5, 15, 20, and 30 kV. Pasteurization results are then tested in fmipa microbiology laboratory to find out the success of the tools that have been made. In each voltage variation it is obtained that all treatments have reached pasteurized milk quality standards based on SNI where at 5kV voltage variation can inactivat microbes up to 83.33%, voltage variation of 10kV can inactivat microbes up to 94.5%, At a voltage variation of 12.5 kV can inactivae microbes up to 83.6%, 15kV voltage variation can inactivae microbes up to 88.8%, while voltage variation of 20 kV can inactivae microbes up to 84.2% and at voltage variation 30 kV can inactivae microbes up to 84.8%.Key Words: PEF, Flyback Transformer, ZVS Driver, Pasteurization.

Measuring complex for determining the characteristics 
 of high-voltage silicon carbide Schottky diodes in impulse modes

This paper describes a developed automated research measuring complex that allows one to determine the parameters of currents, voltages and power of silicon carbide Schottky diodes when applied reverse voltage impulses with amplitudes from 400 to 1000 V. The research 
 measuring complex was tested on DDSH411A91 («GRUPPA KREMNY EL») and C3D1P7060Q (Cree/Wolfspeed) silicon carbide Schottky diodes and allows to determine their 
 maximum values of the rate of rise of reverse voltage dV/dt (877 V/ns and 683 V/ns). Also, the maximum values of the current rise rate dI/dt were determined for DDSH411A91 (3.24 A/ns) 
 and C3D1P7060Q (3.72 A/ns) diodes. For the first time it was established that, when a reverse voltage impulse with an amplitude of 1000 V is applied, the maximum values of instantaneous fullpower reach 1419 VA for the DDSH411A91 diode and 1638 VA for the C3D1P7060Q diode.

Ice nucleation forced by transient electric fields.

Icing affects many technical systems, like aircraft or high-voltage power transmission and distribution in cold regions. Ice accretion is often initiated by ice nucleation in sessile supercooled water droplets and is influenced by several influencing factors, of which the impact of electric fields on ice nucleation is still not completely understood. Especially the influence of transient electric fields is rarely or not at all investigated, even though it is of great interest, e.g., for high-voltage transmission lines or for the food industry. In the present study the impact of transient electric fields on ice nucleation in supercooled sessile water droplets is experimentally investigated under well-defined conditions. A set of droplets is cooled down to a certain temperature and is subsequently exposed to electric fields generated from standard lightning or standard switching impulse voltages, which are commonly used for testing of high-voltage equipment. The nucleation behavior of individual droplets is captured using a high-speed camera and the effect of the transient electric field on ice nucleation is analyzed by considering both the singular and the stochastic nature of nucleation. While the singular nature of nucleation is referred to during analysis of the relative number of droplets remaining liquid long times after the impulse voltage, its stochastic nature is accounted for in the analysis of the temporal evolution of the relative number of frozen droplets. It is shown that low electric field strengths (E[over ̂]≤6.52kV/cm) only have a negligible impact on ice nucleation, independent of the supercooling. In contrast, high electric field strengths (E[over ̂]≥9.78kV/cm) promote significantly ice nucleation. It is also shown that depending on the supercooling, the freezing delay of the different droplets in the ensemble may vary over several magnitudes for the same conditions. It is demonstrated that the electric field appears to indirectly affect the nucleation rate by generating droplet oscillations, finally promoting ice nucleation. The experiments clearly demonstrate the possibility to actively force ice nucleation by applying transient electric fields. These results improve the understanding of ice accretion on high-voltage insulators and may also lend insight into freezing processes in food industry. We expect that these results will be a valuable contribution in formulating and/or validating new nucleation models.

Frequency Optimization of PZT-FBG Voltage Sensor Based on Temperature-Independent Demodulation Method

Fiber grating sensors have been widely used in industry and has been an important research topic in power systems due to their small size, satisfactory electric shielding ability, and high compatibility with optical fibers. Voltage is a crucial parameter that must be monitored in the power system. Existing PZT-FBG voltage sensors are small, inexpensive, and present acceptable linearity in the range of 50 Hz-20 kHz. However, voltages in power systems cover signals with a frequency from DC to MHz and the existing frequency range is insufficient. Finite element method is adopted to improve frequency characteristics of the PZT-FBG sensor and choose the optimal basic structure by initially calculating resonant frequencies. Structural parameters are then selected via dielectric spectrum analysis. The test platform is established to verify amplitude response, frequency response, three-wave response, temperature characteristics, and impulse voltage response of the frequency-optimized PZT-FBG sensor. Test results showed that the sensor presents satisfactory linearity and the temperature-independent demodulation method improves its stability with temperature changes. Impulse voltage tests indicated that the sensor can respond to impulse waveforms with a wave front time of 250 and 10 μs. Hence, the sensor can respond to a voltage signal of 100 kHz with acceptable consistency. The optimization achieved in this study can provide a reference for further improvement of this sensor and other similar sensors with PZTs.

A Method for Endurance Testing of Enameled Round and Rectangular Wires for Motors Controlled by SiC-based Inverters

The purpose of this article is to propose a method for investigating the influence of the impulse voltage waveform generated by inverters based on wide bandgap semiconductors on the insulation endurance of magnet wires. In this regard, endurance tests of enamel insulation are performed on a designed test bench, which generates repetitive voltage pulses with ns-level rising and falling times corresponding to modern silicon carbide-based inverters. Furthermore, we suggest a novel specimen's shape for testing enameled rectangular section magnet wires which find their application in electric traction motors. Considerations related to the deterioration of dielectrics subjected to impulse voltage with high slew rates and high switching frequency are given.

Recovery of Withstanding Voltage After Direct Current Interruption Using Vacuum Circuit Breakers

The recovery characteristics of the withstanding voltage of a vacuum gap are crucial for the development of direct circuit breakers with mechanical switches. In the active-current-injection-type dc circuit breakers, a negative voltage, i.e., a voltage of polarity opposite to that of the interrupting current, is initially applied after current zero caused by the energy stored in the active-current-injection branch. Subsequently, the recovery voltage obtains the same polarity as the interrupting current, namely, it becomes positive as the capacitance around the mechanical switch is charged. In this study, the recovery characteristics of the withstanding voltage for the negative and positive polarity are measured by applying impulse voltage after the current zero of dc interruption simulating current. The recovery of the withstanding voltage for a positive impulse takes a longer time than that of the negative impulse. The recovery of the positive withstanding voltage is determined by the decrease in the temperature of the microprojections on the cathode spot edges. The postarc current analysis shows that the postarc plasma decays with time according to the power law in the time range of 1–50 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> after current zero. Under the dc interruptions, where the current decreasing ratio increases, the residual plasma density after current zero tends to be higher than that under ac interruptions.

Analysis of light emission and Schlieren from short gap high voltage streamers representing lightning impulses

Light emissions and Schlieren structures were simultaneously observed from streamers produced by tens of kilovolts 1.2/50 μs impulses, representing the high voltage component of lightning, applied across a 4 cm air gap between a variety of electrode geometries and a ground plane in an unconfined environment. The results demonstrated that the light emissions and Schlieren structures coincide along the same streamer filaments but on different timescales; the light existing only during the microsecond timeframe impulse whereas the Schlieren continued to develop into the millisecond timeframe, moving towards the centre of the air gap whilst diffusing into the surrounding air within 100 ms. If an electrical breakdown did occur, the Schlieren structures outside the arc remained visible. Streamer formation theory for high voltage impulses is subsequently refined to include the observed Schlieren mechanism.

전계불평등도에 따른 대기압 공기 절연파괴특성 분석

In this study, electrical breakdown characteristics of atmospheric air under the AC and lightning Impulse(LI) voltage waveforms were investigated to settle the electrical insulation design criteria for air insulated switchgear. To investigate the electrical breakdown characteristics according to the non-uniformity of electric field, needle-plane and 4 kinds of sphere-plane electrodes were used as the tested electrode system. Through the experimental results, it was found that when positive impulse voltage is applied, it can be the weakest in terms of electrical insulation. As for the positive LI breakdown voltage, in the case of electrodes with high non-uniformity such as needle-plane electrode, it was confirmed that electrical breakdown voltage increased almost linearly with the gap length. Based on the experimental and electric field analysis results, it is found that it is desirable to establish the air insulation design/evaluation criteria as a function according to the distance in electrodes with high non-uniform electrode systems, and as a maximum electric field function in the quasi electrode systems. Moreover, maximum electric field for partial discharge (PD) inception decreased as the cross-sectional area of the electrodes facing each other increased.

Systematic Design and Circuit Analysis of Lightning Impulse Voltage Generation on Low-Inductance Loads

The well-known circuit for the generation of lightning impulse voltage (LIV) on low-inductance loads was introduced by Glaninger in 1975, and the circuit component selection was proposed by Feser. However, the circuit and the approach for the component selection have some difficulties for which further adjustment is required for obtaining the waveform parameters according to the standard requirement. In this paper, an extended Glaninger’s circuit with an additional series resistor is proposed. Furthermore, a systematic design and circuit analysis of LIV generation for low-inductance loads are developed. With the help of a circuit simulator, the circuit analysis for the component selection is described. The validity of the proposed circuit was confirmed by some experimental results in comparison with the simulated ones. The proposed circuit and component selection provide not only the generation waveform according to the standard requirement but also other promising performances in terms of the wide inductance load range from 400 μH to 4 mH, a voltage efficiency of over 80%, an overshoot voltage of below 5%, an undershoot voltage of below 40%, and a maximum charging capacitance of 10 μF. From the simulated and experimental results, the proposed circuit and component selection approach is very useful for the LIV tests on low-inductance loads instead of using the conventional approach based on trial and error.

A testing method with steep impact voltage inspecting the internal defects in EMU roof cable termination

A high-voltage cable terminal on the roof of a high-speed electric multiple unit operates in an intermittent impact load environment. The internal defects of the cable terminal are accelerated and are likely to cause insulation failure. Therefore, in this study, a steep impact voltage method is proposed to identify defective cable termination and establish a thermal and electric field model of the cable termination to analyse the defect development process. The results demonstrated that the interface performance of the cable terminal decreased after operation, and the internal insulation broke down under a steep-wave impulse voltage. Under the operating voltage, there was an electric field concentration at the interface between the stress layer and the insulation layer of the cable terminal that can cause partial discharge within the defect located in this part. The thermal field distortion at the cable terminal joint was obvious, and the resulting air gap reduced the interface performance. Field distortion aggravates the insulation damage under frequent thermal shock and causes insulation accidents. This study provides an experimental reference and theoretical basis for the design and operation of cable terminations.

Experimental Evaluation of 3D Tortuosity of Long Laboratory Spark Trajectory for Sphere-Sphere and Sphere-Plane Discharges under Lightning and Switching Impulse Voltages

Evaluation of attractive areas of high- and ultra-high voltage power transmission lines to direct lightning strokes is based on modeling of propagating progress of the lightning leader approaching the transmission line. The aim of the modeling is to determine the effectiveness of lightning protection for a given line design. The statistical models are currently being developed to extend the conventional deterministic models by embracing the randomness of the discharge channel in space and hence to reproduce the statistical distribution of the striking points. These models require experimental data for understanding of the lightning leader development process and to validate the model across the measurement data. This paper reports on the measured trajectories of discharge channels of long laboratory sparks in various high voltage laboratory arrangements. The sparks were initiated by switching and lightning impulses with peak values ranging from 1200 kV to 3364 kV of positive and negative polarity for two types of high-voltage electrode systems (sphere-sphere and sphere-plane), arranged at distances of 3.3 m and 5.5 m from each other. Statistical distributions of angles describing trajectory of discharge channels in space are reported for a total number of 540 recorded discharges. The results can serve as reference measurement data to develop and evaluate the accuracy of simulation models incorporating statistical nature of the lightning leader development process.

Development of a pulse-induced electrochemical biosensor based on gluconamide for Gram-negative bacteria detection.

Pathogenic bacteria can cause the outbreaks of disease and threaten human health, which stimulates the development of advanced detection techniques. Herein, a specific and sensitive electrochemical biosensor for Gram-negative bacteria was established based on the conductive polymer with artificial muscle properties. Theeffective recognition was achieved through the specific carbohydrate-carbohydrate interaction between gluconamide and lipopolysaccharide. Theapplication of impulse voltage enhances the efficiency of recognition and shortens the detection time through the temporary deformation of the electrode surface, with a limit of detection (LOD) of1 × 100CFU/mL anda linear range of 1 × 100 - 1 × 106CFU/mL for Escherichia coli (E. coli). In addition tothe merits of low cost, high efficiency, and rapidity, the developedlabel-free electrochemical biosensor can also be applicable for other Gram-negative bacteria, owning promising potential in the application of portable devices and paving a potential way for the construction of electrochemical biosensors.

Effect of Concentration of Al2O3 Nanoparticles on Electrical Properties of Mineral Oil

This study aimed to compare the electrical characteristics of mineral oil-based nanoparticles to those of pure mineral oil. Mineral oil used in distribution transformers was mixed with aluminum oxide (Al2O3) nanoparticles, which serve as an insulator, with 0.01, 0.03, and 0.05 % mineral oil volume concentrations. The moisture content in mineral oil was measured beforehand, and the electrical tests were subsequently conducted in accordance with international standards. The moisture content test revealed that the combination of nanoparticles and mineral oil resulted in an increase in moisture content. As regards the test of AC withstanding voltage and negative polarity lightning impulse voltage, it was found that the mineral oil mixed with the nanoparticles had higher dielectric strength than the original mineral oil. In addition, the test results of positive polarity lightning impulse voltage demonstrated that with a mixture of mineral oil and the nanoparticles at a 0.01 % concentration, the positive polarity lightning impulse dielectric strength of the mineral oil increased. However, at concentrations of 0.03 and 0.05 %, it did not rise, regardless of the increasing volume of nanoparticles. The results, thus, showed promising directions for applications of nanoparticles in the development of electrical properties of mineral oil. HIGHLIGHTS The addition of Al2O3 nanoparticles to the mineral oil resulted in an increase in the oil moisture content. However, it was found that the moisture content in the mineral oil tended to decrease with the increase in the amount of nanoparticles The optimum nanofluid combination in terms of increased AC breakdown strength was created by adding Al2O3 nanoparticles to mineral oil at a rate of 0.05 vol% The Al2O3 nanoparticles being added to the mineral oil can give an increase in the impulse breakdown voltage with the negative polarity For the positive polarity of the impulse breakdown voltage, the best nanofluid mixture in terms of increased breakdown strength was produced by the addition of Al2O3 nanoparticles at a rate of 0.01 vol% to the mineral oil GRAPHICAL ABSTRACT

Surface flashover patterns of GIS basin insulator under impulse voltage

Basin insulator is an important component of SF6 gas insulated switchgear (GIS), and its fault is also one of the major causes of GIS equipment failure. Due to the large capacity of high voltage power system, the faulty basin insulators are generally burned severely by the high energy arc, so the fault diagnosis is very difficult. In this paper, the surface flashover pictures of several full-scaled GIS basin insulators under impulse voltage are collected, and the morphology features of flashover traces initiating from different positions are summarized. As a result, the surface flashover patterns are divided into three types: 1) surface of shielding electrode initiated flashover, 2) triple junction initiated flashover and 3) surface of insulator initiated flashover. The inception and development process of flashover are also summarized. Besides, the diagnosis method of discharge inception position is proposed. Firstly, check the ablation points at high voltage terminal. If there is a ablation point on the surface of shielding electrode, the flashover initiates from there. If there is only ablation point at the triple junction, the inception position depends on the flashover trace morphology: when the flashover trace disperses in a single direction towards grounding electrode or high voltage electrode, the flashover initiates from the opposite triple junction; when the flashover trace disperses towards both electrodes, the flashover initiates from the insulator surface. The dispersion direction could be directly distinguished from the black carbonized dendritic traces, or from the “white dendritic traces” with the auxiliary methods. The conclusions could help the substation maintenance staff do the root cause analysis of the surface flashover, and assist the researchers in the structural optimization design of basin insulator.

Oscillation of Gas Density in the Gas Filament Remained by a Streamer Discharge in Water

When a streamer discharge occurs in water, several luminous plasma filaments will be created in the water during the discharge. After the discharge, these plasma filaments turn into neutral gas phase and remain in water. The gas filament remained in water is a good object for studying the basic processes involved in the streamer propagation. We investigated the evolution of the gas filaments remained in water after a streamer discharge at different experimental conditions. We recorded eight successive images during one discharge pulse. The density of gas in the gas filament and the radius of the gas filament were measured from the obtained images. We found that the radius of the gas filament and the density of gas in the gas filament are almost not influenced by the impulse voltage within the range studied. While the conductivity of water has strong effect on the radius of the gas filament and the density of gas in the gas filament. The radius of the gas filament becomes thicker and expands faster as the conductivity of water becomes larger. The density of gas in the gas filament remained in water oscillates between 400 to 800 kg/m3 with an duration of ~10 μs during the expansion period of 4–39 μs after the HV pulse starts. Both the impulse voltage and the conductivity of water do not affect the oscillation duration of the density of gas in the gas filament.

Response of Drone Electronic Systems to a Standardized Lightning Pulse

This paper presents the results of experimental tests of the impulse response of selected, essential components of a drone. A standardized lightning pulse that is often used during immunity tests of electronic devices in the aviation industry was applied. A single-stroke voltage impulse generator, MIG0618SS, was capable of producing the desired pulses. The input voltage was injected into selected electronic circuits of the drone system and pulses were observed in different parts of the machine. This allowed us to build a model based on the transmittance of the circuits most exposed to lightning overvoltages. The conducted tests were supported by impedance measurements carried out with an LCR-8110G meter. The obtained results made possible the development of a preliminary drone simulation model, allowing us to determine the size of the disturbances arising in individual circuits during nearby lightning. A discussion of the influence of close lightning discharges on expected induced overvoltages in a drone electronics system is also conducted in the paper.

FREQUENCY CHARACTERISTICS OF ELECTRICAL MACHINES WITH A MESH WINDING DURING HEAT-AND-MOISTURE AGING

&#x0D; &#x0D; &#x0D; &#x0D; Operation of an electric drive with damages in power electric circuit of the motor stator results in asymmetry&#x0D; &#x0D; &#x0D; &#x0D; &#x0D; of the motor phase current charge, increase of heating losses in certain phases, occurrence of variable components of electromagnetic torque and consumed power. An electric motor stator winding consists of a number of stator bars and overhang connections. Due to the complicated winding structure and the steel core, the attenuation and distortion of a pulse transmitted through the winding are complicated, and frequency-dependent. A low voltage impulse method and digital analysis techniques to determine the frequency characteristics of the winding are described. The frequency characteristics of electric motor stator windings are discussed in some detail. The analysis presented in this chapter could be applied to other rotating machines such as low voltage motors. An experiment of damping of electric motor wilding was conducted. Changes in frequency characteristics after the cycle are shown. In this article an analysis of the frequency characteristics of low-voltage electric machines with mush-wound windings, taking into account the processes of successive destruction of the insulation structure by the influence of heat-wet cycles. It is shown that the frequency characteristics can be generalized by the parameter of the state of isolation in the conditions of periodic monitoring of the quality of insulation during regulatory audits. It is proved that the frequency characteristics taken in idle and short-circuit modes have diagnostic features of the level of insulation destruction during humidification, which consist of shifting the characteristics of extremes into the region of lower frequencies, as well as reducing the area under the curve between the minimum and maximum extrema of the characteristic.&#x0D; &#x0D; &#x0D; &#x0D;

Temperature Gradient Affecting Electrical Tree in Silicone Rubber under Impulse Superimposed on DC Voltage

In this paper, the electrical tree growth characteristics of silicone rubber (SiR) are studied under impulse superimposed on DC voltage and a temperature gradient (TG) field. The temperature difference between high voltage (HV) and ground (GD) electrodes varies from -90 to 90 °C resulting in a TG field in the samples. The electrical tree morphology, length and accumulated damage are discussed. Experimental results show that with the increase of absolute value of TG, the electrical tree length and accumulated damage continue to increase, and the tree morphology turns from branch-like tree to bush-branch hybrid tree. The positive TG has a more obvious acceleration effect on the tree growth than does the negative TG. Under the TG, the temperature dependent carrier transport results in space charge accumulation and electric field distortion at low temperature side, which is the main reason for the different growth characteristics of electrical tree. Besides, the accumulated damage of DC superimposed with heteropolar impulse voltage is larger than that under DC superimposed with homopolar impulse voltage. It is concluded that the temperature gradient and impulse superimposed on DC voltage promote the electrical tree growth of HVDC cable accessories insulation.

Nonvolatile voltage-controlled magnetization reversal in a spin-valve multiferroic heterostructure

Pure voltage-controlled magnetism, rather than a spin current or magnetic field, is the goal for next-generation ultralow power consumption spintronic devices. To advance toward this goal, we report a voltage-controlled nonvolatile 90° magnetization rotation and voltage-assisted 180° magnetization reversal in a spin-valve multiferroic heterostructure. Here, a spin valve with a synthetic antiferromagnetic structure was grown on a (110)-cut Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-PT) substrate, in which only the magnetic moment of the free layer can be manipulated by an electric field (E-field) via the strain-mediated magnetoelectric coupling effect. As a result of selecting a specified PMN-PT substrate with defect dipoles, nonvolatile and stable magnetization switching was achieved by using voltage impulses. Accordingly, a giant, reversible and nonvolatile magnetoresistance modulation was achieved without the assistance of a magnetic field. In addition, by adopting a small voltage impulse, the critical magnetic field required for complete 180° magnetization reversal of the free layer can be tremendously reduced. A magnetoresistance ratio as large as that obtained by a magnetic field or spin current under normal conditions is achieved. These results indicate that E-field-assisted energy-efficient in-plane magnetization switching is a feasible strategy. This work is significant to the development of ultralow-power magnetoresistive memory and spintronic devices.