High-voltage Impulse Research Articles

Cascoded HBT pair: A new method of generating subnanosecond high‐voltage impulses

AbstractIn this letter, a fully integrated subnanosecond high‐voltage impulse generator using 2‐μm GaAs HBT process is presented. The core circuit consists of a cascoded HBT pair with an inductor and it works on two principles: a faster transition can be obtained from a digital logic input into the HBT and a differentiation of the very fast transition current using the inductor to generate a large voltage at the output. Measurement results show the generated impulses have a tunable peak voltage between 0.5 and 3.2 V with a full‐width‐half‐maximum (FWHM) of 100 ps. The impulse generator is biased from a 3.3 V battery supply and consumes 15 mW at 1 MHz pulse repetition rate (PRF). © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1683–1685, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25295

The influence of high-voltage impulse treatments on biological cells

Present article to influence of high pulsed electrical fields on microorganisms in water-containing medium is dedicated. A spherical model of organule by two-layer dielectric membrane is considered. The accounts and diagrams of dependence of field intensity on organule membrane from its geometrical and dielectric parameters are given. The necessity of influence by nanosecond high voltage pulses on microorganisms for their full inactivation is shown.

토양의 이온화영역에서 소규모 접지전극의 과도접지임피던스 특성 분석

This paper presents measurement results of transient impedance for small-sized ground electrodes in a discharge region of soil. For a realistic analysis of ionization characteristics near the ground electrode, three types of ground rod installed outdoors and high voltage impulse generator were used for injecting test current. From the analysis of response voltage and current flowing ground electrode to earth, it is verified that the ionization near the ground electrode contributes to reduction of ground impedance and limits the ground potential rise effectively in high resistivity soil. As a threshold electric field density for ionization is small in low resistivity soil, the shape of ground electrode rarely contributes to the transient impedance. And, from the experiment result with shape of ground electrode, the rod with needles is more effective to reduce the transient impedance than the plate electrode in the voltage range including with ionization regions of soil.

A Study on the Impact of Low-Amplitude Oscillatory Switching Transients on Grid Connected EHV Transformer Windings in a Longitudinal Power Supply System

Switching events in inter connected power systems have significant effects on EHV transformers. Standard high-voltage lightning and switching impulse tests are performed on EHV transformers during manufacture, to ascertain breakdown strength of insulation used. But, during their service, transformers encounter numerous voltage transients of complex and varying wave shapes which do not necessarily resemble these standard surge type voltages. Transformers are complex assembly of coils around magnetic core having inductances and capacitances and therefore, exhibit unique frequency response characteristics with several natural resonate frequencies. Oscillatory overvoltages originating in power systems due to switching, faults and other phenomena often traverse through transformers and can excite one or more of the winding's natural resonate frequencies resulting severe internal voltage amplification and damage to insulation even when the terminal excitation voltages have relatively low amplitude. Adequate consideration must therefore be given to such low amplitude oscillatory transient voltages while designing insulation for grid connected EHV transformers. In this paper, the authors have analyzed the voltage stresses developed in the windings of a 400/220/33-kV grid connected transformer operating in the Eastern Regional Power Grid of India, when natural frequencies of the transformer winding are triggered by oscillatory switching transients. The developed voltage stresses have been compared with those under standard laboratory dielectric tests including newly incorporated fast front-long tailed switching surges.

A Proposal for Concurrent Estimation of Static and Dynamic Nonlinearity of ADC

Despite great advances in very large scale integrated-circuit design and manufacturing, performance of even the best available high-speed, high-resolution analog-to-digital converter (ADC) is known to deteriorate while acquiring fast-rising, high-frequency, and nonrepetitive waveforms. Wave-form digitizers (ADCs) used in high-voltage impulse recordings and measurements are invariably subjected to such waveforms. Errors resulting from a lowered ADC performance can be unacceptably high, especially when higher accuracies have to be achieved (e.g., when part of a reference measuring system). Static and dynamic nonlinearities (estimated independently) are vital indices for evaluating performance and suitability of ADCs to be used in such environments. Typically, the estimation of static nonlinearity involves 10-12 h of time or more (for a 12-b ADC) and the acquisition of millions of samples at high input frequencies for dynamic characterization. ADCs with even higher resolution and faster sampling speeds will soon become available. So, there is a need to reduce testing time for evaluating these parameters. This paper proposes a novel and time-efficient method for the simultaneous estimation of static and dynamic nonlinearity from a single test. This is achieved by conceiving a test signal, comprised of a high-frequency sinusoid (which addresses dynamic assessment) modulated by a low-frequency ramp (relevant to the static part). Details of implementation and results on two digitizers are presented and compared with nonlinearities determined by the existing standardized approaches. Good agreement in results and time savings achievable indicates its suitability.

Stability of Step-Response Parameters of Standard Impulse Voltage Divider for Lightning Impulse

Long-term stability of step-response parameters of the standard voltage divider may be useful in evaluating the long-term stability of the standard measuring system for high voltage impulse, which influences the uncertainty of the system . Because dispersions of the step-response parameters have been large, they have not been considered in evaluating the uncertainty of the system. Dispersion of the experimental response time is largely due to noise superimposed on measured step-response waveforms. It can be reduced either by increasing sampling rates of the waveform or by improving the signal to noise (S/N) ratio. Dispersion of the partial response times is due to oscillations on the wavefront of step-response waveforms. Calculation of the virtual origin becomes unstable in the presence of the oscillation, resulting in the dispersion of the partial response time.

Inductive Pulsed-Power Supply With Marx Generator Methodology

We have been developing an inductive pulsed-power supply consisting of many coils with Marx generator methodology. A Marx generator is charged in a parallel connection of capacitors and discharged in a series connection to obtain a high-voltage impulse. In contrast, this inductive pulsed- power supply is excited in a series connection of coils and discharged in the parallel connection to obtain a pulsed large electric current. Our preliminary experiment showed that this process was correct. As the next step, we have developed a prototype of the inductive pulsed-power supply, which we call the current multiplier by inductive storage (CMIS). Here we describe the CMIS characteristics and the results of experiments using CMIS.

임펄스전압에 의한 동심원통형 전극계에서 토양 이온화특성 분석

본 논문은 뇌임펄스전압에 의한 토양의 이온화 현상과 모델접지시스템의 과도적 특성에 관련된 파라미터에 관한것으로 건조 모래와 습한 모래에 대한 이온화 특성을 치수가 다른 동심원통형 전극계의 실험 용기를 이용하여 연구하였다. 결과로써, 높은 임펄스전압이 인가된 모래의 비선형 전기적 특성은 이온화 과정에 의해 발생하였다. 모래의 과도임피던스는 수분의 함유량과 인가임펄스전압의 크기에 의존하며, 수분의 함유량과 인가전압의 크기의 증가에 따라 접지임피던스는 감소하였다. 본 연구결과는 뇌서지에 대하여 우수한 성능을 가지는 접지시스템의 설계에 유용한 정보가 될 것이다.

Effects of a high-voltage electrical impulse and an anticancer drug on in vivo growing tumors.

Application of a high-voltage electrical impulse (5 kV/cm, 2 msec) after bleomycin administration resulted in a significant size decrease of subcutaneously inoculated AH-109A hepatocellular carcinoma in Donryu rats. The tumor size decreased to an average of 17% of the initial mass 4 days after the treatment. Neither the high-voltage electrical impulse nor bleomycin administration alone showed an inhibitory effect on the tumor growth. It was concluded that the concomitant use of a high-voltage electrical impulse and an anticancer drug has the potential to be applicable for cancer treatment.

Electric-discharge cutting of rocks

The test data are reported on rock cutting by the electric discharge with movable and stationary electrodes. The specific crushing energy is determined, the electrode system design is optimized, and the high-voltage impulse parameters selected for highly efficient fracture. The study results make the grounds to develop an electric-discharge cutter for rocks and concrete.

FDTD Analysis of the Unit Step Response of a Circuit Measuring Chopped Lightning Impulse Voltages

Unit step response (USR) parameters of a circuit for measuring chopped lightning impulse voltages are calculated using the finite-difference time-domain method for solving Maxwell's equations, and compared with those of a USR-measuring circuit recommended by the International Electrotechnical Commission (IEC). Although the circuit for measuring chopped lightning impulse voltages is quite different from the IEC-recommended USR measuring circuit, USR parameters calculated for the former circuit are not much different from those calculated for the latter circuit except the case when the former circuit includes both a low-impedance impulse high voltage generator and a damping resistor.

Digital measurement system for high-voltage impulse tests on transformers

More information from test data can be obtained when digital measuring techniques are used. A description of a tailor made measurement system in use by a Dutch high-voltage laboratory is presented. Schematic diagrams of the test setup and the measurement system are shown and the precautions taken to avoid electromagnetic compatibility (EMC) problems are described. Software facilities and their realization are described together with algorithms for waveshape determination. The use of a digital signal processor board for transfer function calculations is explained. Examples of tests with full and chopped lightning impulses are presented both in time and frequency domain.

Establishment of National Standard on High Voltage Impulse Measurement

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Piezoelectrets from thermo-formed bubble structures of fluoropolymer-electret films

Cellular and porous polymers with internal bipolar space charge can exhibit large piezoelectric thickness coefficients and have therefore led to significant advances in the understanding and the application of piezoelectricity in polymer electrets. As possible alternatives to these cellular ferroelectrets, other potentially useful configurations of space-charge electrets, such as bi-layer or multi-layer stacks of at least one soft porous and one hard non-porous electret film have been suggested and investigated. Extending the concept of cellular or porous polymer electrets with microscopic voids, we propose and describe novel piezoelectret structures with regular arrays of millimeter-sized bubbles that are formed between fluoro-ethylene-propylene (Teflonreg-FEP) films via a vacuum-assisted thermal process. After internal charging by means of high impulse voltages, the bubble structures exhibit rather large piezoelectric activities in their thickness direction, with phenomenological quasi-static d33 coefficients of up to 500 pC/N (or pm/V) which quite strongly decrease with the amplitude of the applied force. The electromechanical behavior of the new piezoelectrets has been modeled in analogy to the operation of electret microphones

Piezoelectrets from thermo-formed bubble structures of fluoropolymer-electret films

Cellular and porous polymers with internal bipolar space charge can exhibit large piezoelectric thickness coefficients and have therefore led to significant advances in the understanding and the application of piezoelectricity in polymer electrets. As possible alternatives to these cellular ferroelectrets, other potentially useful configurations of space-charge electrets, such as bi-layer or multi-layer stacks of at least one "soft" porous and one "hard" non-porous electret film have been suggested and investigated. Extending the concept of cellular or porous polymer electrets with microscopic voids, we propose and describe novel piezoelectret structures with regular arrays of millimeter-sized bubbles that are formed between fluoro-ethylene-propylene (Teflonreg-FEP) films via a vacuum-assisted thermal process. After internal charging by means of high impulse voltages, the bubble structures exhibit rather large piezoelectric activities in their thickness direction, with phenomenological quasi-static d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">33</sub> coefficients of up to 500 pC/N (or pm/V) which quite strongly decrease with the amplitude of the applied force. The electromechanical behavior of the new piezoelectrets has been modeled in analogy to the operation of electret microphones

HV Impulse Measuring Systems Analysis and Qualification by Estimation of Measurement Errors via FFT, Convolution, and IFFT

Quality of high-voltage (HV) impulse measurements requires adequate dynamic performance of measuring systems (MS) with respect to the waveforms to be measured. Qualification of MSs for various impulses is a prerequisite for repeatability and reproducibility of HV testing results. Alternative qualification procedures are considered with respect to the standard full lightning impulse including evaluation of significance of its frequency components. Duality of step responses and amplitude-frequency responses is described in detailed examples. Special attention is paid to creeping, encountered with some converting devices. Variations of MS response parameters can lead to improper conclusions when only conventional examination of the dynamic behavior is used. Evaluation of the response parameters is an unnecessary step, which brings additional errors to the HV measurements. The paper is pointing out advantages and practical achievements of the frequency-domain qualification of dynamic properties based on the step response data obtained both experimentally and analytically. Measurement errors of the impulse peak value and time parameters have been evaluated via fast Fourier transform (FFT), convolution, and inverse discrete Fourier transform (IFFT) for a commercial divider. Direct determination of the HV impulse measurement range, no need for any additional parameters, and illustrative graphical presentation of results are the main advantages of this approach. Limitations of different qualification approaches are discussed.

Dual-Choice Testing of the Discharge-Stroke Susceptibility of Bare- and Insulated-Line Conductors

This paper reports on the relative vulnerabilities of bare- and insulated-line conductors to hits from discharge strokes coming from sources at voltages too high to prevent flashovers, like lightning. Protection against such strokes must be based on diversion strategies, where the conductor to be protected is made as unattractive as possible compared to alternative, usually grounded conductors nearby. As a first attempt to quantify this discharge-stroke susceptibility for some commonly used line conductors, we have performed measurements where high-voltage impulses, applied to a rod 1-2 m above a ground plane, launch streamer-leader sequences propagating downwards toward a wire or insulated cable or both, suspended horizontally 0.25-0.5 m above the ground plane. The ensuing will thus always have a dual choice, either between the wire/cable and ground, or between the wire and the cable. The percentage of hits to the wire/cable is counted and plotted as a function of the sideways displacement of the wire/cable from the rod axis, and is a measure of the spark appeal of the wire/cable. The measurements confirm that streamers emitted from an object are especially important for attracting sparks from negative sources. Our results indicate that three-phase overhead lines should be as thick and as closely spaced as possible to minimize lightning-stroke risks. The effect of line insulation is both to increase the effective thickness and to permit closer spacing between the phases.

Low energy single stage high voltage impulse generator

High voltage (HV) impulse generators are employed widely for testing of HV apparatus, as such tests are codified in a range of standards. As a result, insulation properties under impulse waveforms are of interest in the design of HV apparatus. This creates a need for very low energy laboratory impulse generators which can be used to test laboratory scale samples, often in conjunction with sensitive electronic instrumentation to measure sample dielectric properties. Since the sample is often the only isolation between the impulse generator and the electronics, failure of the sample will result in exposure of the electronics to the energy stored in the generator. This paper provides design details for a very low energy (/spl sim/1 nF storage), single-stage impulse generator which provides clean double exponential waveforms.

On the accuracy of high impulse voltage measurements

Measurements and tests on solid dielectrics with lightning or switching impulses have received considerable attention because they are concerned in the optimal design of internal insulation for high voltage apparatus. Accuracy of measurements relating to the above phenomena is generally deemed very important. In this paper a model is proposed and an investigation is attempted regarding the accuracy of such measurements. The results are confirmed through laboratory measurements. According to the results presented, the value of the grounding resistance is a crucial parameter that affects measurement accuracy; it must never exceed the value of 0.5 Ω.

On the accuracy of high impulse voltage measurements

Measurements and tests on solid dielectrics with lightning or switching impulses have received considerable attention because they are concerned in the optimal design of internal insulation for high voltage apparatus. Accuracy of measurements relating to the above phenomena is generally deemed very important. In this paper a model is proposed and an investigation is attempted regarding the accuracy of such measurements. The results are confirmed through laboratory measurements. According to the results presented, the value of the grounding resistance is a crucial parameter that affects measurement accuracy; it must never exceed the value of 0.5 Ω.