High-voltage Impulse Research Articles

The Effect of High Voltage Impulses on PVC-Graphite Polymer Thick Film Resistors

This paper describes the effect of electric high voltage impulses on PVC-Graphite thick film resistors. It has been found that the resistance generally decreases with increase in number of high voltage impulses or impulse width, when the high voltage impulses amplitude is above the threshold value. It has also been found that the resistance decreases with increasing high voltage impulses amplitude above certain impulse amplitude (threshold). Two types of change were observed: reversible and irreversible. Experimental results on the resistors are discussed in terms of resistivity vs firing parameters.

Experience With Online Partial-Discharge Measurement in High-Voltage Inverter-Fed Motors

Partial-discharge (PD) testing has long been an important tool for assessing the condition of the high-voltage insulation in motor and generator stator windings. In the past several years, many motors have been powered from inverters, which facilitate variable-speed motor operation. The most common drive used today is the voltage-source pulse-width modulation (VS-PWM) type. VS-PWM drives rated up to 13.8 kV are becoming more common in natural gas processing plants, as well as in other petrochemical facilities. Such drives generate high-voltage impulses in the kilovolt range with rise times in the submicrosecond range. These impulses are a form of severe electrical interference that can make difficult the online detection of PD (with magnitudes 1000 times smaller) due to the overlapping frequency content in PD and in the impulses. Thus, PD detection on medium-voltage VS-PWM systems has been a challenge in spite of the serious stator winding insulation aging that such drives may cause to these motors. This paper discusses the stator winding failure mechanisms that produce PD, including the insulation problems that VS-PWM drives can accelerate. A research project that lasted several years is reviewed. This project culminated in a prototype online PD monitoring system suitable for motors fed by VS-PWM drives.

Генератор високовольтних імпульсів електроогорожі з системою керування на основі мікроконтролера

Генератор високовольтних імпульсів електроогорожі з системою керування на основі мікроконтролера

Effect of operating conditions of high voltage impulse on generation of hydroxyl radical

Effect of operating conditions of high voltage impulse on generation of hydroxyl radical

APPROXIMATE CALCULATION OF BASIC CHARACTERISTICS OF PLASMA AT THE AIR ELECTRIC EXPLOSION OF METAL CONDUCTOR

Purpose. Obtaining approximate calculation correlations for determination of maximal values of temperature Tm, and pressures Pm at a shock wave and speed vm distribution of a shock wave in the plasma products of air electric explosion (EE) of metall conductor under act of large impulsive current (LIC). Methodology. Theoretical bases of the electrical engineering, scientific and technical bases of electrophysics, thermal physics and electrophysics bases of powerful high-voltage impulse technique, related to the theory and practice of the phenomenon EE metallic explorer in gas environments under action of LIC. Results. New calculation correlations are got for approximate calculation in a local area of EE in atmospheric air of metallic explorer of maximal values of temperature Tm,, pressures Pm and speeds of vm of shock wave in «metallic plasma» appearing from an explosion under action of LIC of its conducting structure. It is set that numeral values of the sought after sizes of temperature Tm,, pressures Pm and speeds vm as it applies to air EE thin copper conductor under the action of LIC of the microsecond temporal range can arrive at a few ten of thousands of Kelvin, hundreds of technical atmospheres and thousands of meters in a second accordingly. It is shown that similar values of speed vm of shock wave in «metallic plasma» are comparable at speed of detonation wave in hard explosives. An accent is in this connection done on expedience of application air EE thin short metallic conductors at injury of live ammunitions with an ordinary and nuclear explosive. The real technical suggestions are offered on a possible receipt in the discharge circuit of powerful high-voltage generator of LIC of condenser type of «record» (most) values of the examined descriptions of «metallic plasma» at air EE thin metallic conductors. Comparison of the obtained results is executed for the probed descriptions of plasma at air EE of the metal conductor with known in the world information in area of electrophysics and thermal physics EE metal in gas environments. Originality. The obtained new theoretical results in area of high-current electrophysics and high-temperature thermal physics extend our physical views about the phenomenon of EE in atmospheric air of thin metallic conductors under action of LIC of the nanosecond and microsecond duration. Practical value. Application of the calculation correlations obtained in practice for the indicated descriptions of «metallic plasma» will allow technicians-and-engineers in a certain measure to accelerate and improve adjusting of difficult electric charts of powerful high-voltage generator of LIC at a receipt in his discharge circuit by air EE of thin metal conductors required on protocol of lead through of heavy-current electrophysics experiments of parameters of plasma in the local zone of its explosion.

Structure pattern peculiarities and electrical characteristics of surface dielectric barrier discharge in air driven by impulse and sine high voltage

Structure patterns and electric characteristics of surface dielectric barrier discharges in air driven by periodic unipolar impulse voltage with ns front duration and sine voltage of the same frequency f = 15 kHz are presented. An influence of voltage impulse polarity, amplitude and impulse duration on discharge characteristics is shown to exist. The currents extracted from the surface discharge plasma layer by d.c. voltage of additional third electrode are found to depend on the waveform of the applied high voltage impulses.

Reconfiguration of 3 MV Marx Generator into a Modern High Efficiency System

High voltage impulse generators are intended to last for long periods of time. Upon reaching the end of their technical lifetime, decisions concerning decommissioning, replacement, refurbishment or upgrading are needed. A new generator is a considerable investment. Significant reductions in material and labor costs can be made by repurposing still functional elements of the existing generator and redesigning the circuit for higher efficiency requiring fewer components. This paper describes the process of refurbishing the Mississippi State University (MSU) High Voltage Laboratory 3 MV, 56 kJ impulse generator originally built in 1962 into a modern digital impulse generator system.

Effect of High Voltage Impulses on Surface Discharge Characteristics of Polyethylene

This paper investigates the influence of high voltage impulses on the surface discharge characteristics of polyethylene (PE) during subsequent application of 50 Hz AC voltage. The investigation is done on two types of PE to examine the generality of the phenomena. The effect of impulses on the surface discharge features of PE are studied for both cases of having either a streamer or flashover. For each case, the consecutive surface discharges behave differently when the insulation has been exposed to the transient voltages. The effect of impulses on surface discharge of PE is shown by the change of PD numbers and phase-resolved PD patterns. The results show a prompt change in the total number of discharges which decays with the time. After a surface flashover has occurred due to the impulse, the PD behaves quite differently compared to the similar case without flashover.

APPROXIMATE CALCULATION OF ACTIVE RESISTANCE AND TEMPERATURE OF THE PULSE ELECTRIC ARC CHANNEL IN A HIGH-CURRENT DISCHARGE CIRCUIT OF A POWERFUL HIGH-VOLTAGE CAPACITOR ENERGY STORAGE

Purpose. To obtain calculation correlations for active resistance Rce and maximal temperature Tme of plasma channel of pulse electric arc in the air double-electrode system (DES) with metal (graphite) electrodes, and also practical approbation of the obtained correlations for Rce and Tme in the conditions of high-voltage laboratory on the powerful capacity energy storage (CES) of electric setting, intended for reproducing on the electric loading of protracted C- component of current of artificial lightning with the USA rationed on normative documents by amplitude-temporal parameters (ATP). Methodology. Electrophysics bases of high-voltage impulse technique, scientific and technical bases of development and creation of high-voltage high-current impulse electrical equipment, including powerful CES, and also measuring methods in discharge circuits of powerful high-voltage CES of pulse currents of millisecond temporal range. Results. On the basis of engineering approach the new results of approximate calculation of values of Rce and Tme are resulted in the plasma channel of pulse electric arc discharge in air DES of atmospheric pressure with metallic (graphite) electrodes. Practical approbation of results of calculation of values of Rce and Tme is executed as it applies to air DES, to connected in a discharge circuit of powerful high-voltage CES with protracted C- of component current of artificial lightning, characterized rationed ATP. It is shown that calculation of numeral value Rce approximately in 100 times exceeds the proper value of active resistance for the plasma channel of impulsive spark of electric discharge in air DES other things being equal, and a calculation of numeral value Tme well corresponds with the known thermodynamics information for classic electric arc in air DES of atmospheric pressure with graphite electrodes. Originality. New engineering approach is developed for the approximate calculation of values of Rce and Tme in electron-ion plasma of channel of pulse electric arc, arising in air DES of high-current discharge circuit of powerful high-voltage CES of proof-of-concept of electric setting of the technological setting. A formula is first obtained for the approximate calculation of equivalent active resistance of Rce of channel of pulse electric arc in air DES, remaining unchanging in the process of high-current discharge on RL- load of indicated CES. Practical value. Drawing on the got calculation results for the values of Rce and Tme in high-voltage impulse technique provides the rational choice of own electric parameters and construction elements of basic devices of powerful high-voltage CES of technological of electric setting, and also account of influence of electrical engineering descriptions of air DES on electromagnetic processes, taking place in the high-current discharge circuit of indicated CES with protracted C- of component current of artificial lightning.

Characteristics of the effect of an impulse supply voltage on the structure and characteristics of a surface discharge

Results of an experimental investigation of surface barrier discharge in a three-electrode system are presented. An analysis is done of the flow intensity of charged species extracted from the plasma layer of the surface discharge by the field of high dc potential of the third electrode. A high unipolar periodic impulse voltage of 15-kHz frequency, impulse duration from 0.5 to 45 ms, and 150-ns impulse-front duration is used to form the surface discharge. A It is revealed that the voltage-impulse duration has a significant effect on the intensity of charged species flow (extracted current), the character of the influence being dependent on the voltage-impulse polarity. The influence of voltage-impulse duration on the surface-discharge current is revealed as well. Pictures of the structure of surface discharge at the rise and the fall of the voltage impulse made by means of a high-speed camera are presented. The difference of the discharge structure for different polarities of voltage impulse is revealed. It is suggested that the surface-discharge characteristics are dependent on a combination of a number of factors, such as the parameters of the impulse voltage, volume charge in the gas gap, and the charge on the barrier surface, as well as the material and surface structure of the barrier.

Degradation effects on single crystalline silicon photovoltaic modules subjected to high impulse‐voltages

Scope of the current study is to examine the electrical characteristics of photovoltaic (PV) modules after being subjected to high impulse voltages, which are usually generated by lightning or switching surges. Tests were conducted at the High Voltage Laboratory of the University of Patras in Greece on PV modules of 5 and 195 Wp derived from different manufacturers, by performing various stress scenarios. The I-V and P-V characteristic curves of the examined modules, before and after the impulse voltage stress tests, are compared with each other considering the modules' ability to maintain their nominal electrical characteristics. After certain periods of time, the electrical performances of the stressed modules are examined again in order to ensure whether they regain some or all of their properties in case of prior differentiation. The experimental results are compared with theoretical estimations, so as to confirm the rightness of the presented procedure.

Solubilization of wasted sludge using high voltage impulse technique

Solubilization of wasted sludge using high voltage impulse technique

High Voltage Discharge Profile on Soil Breakdown Using Impulse Discharge

Grounding terminals are mandatory in electrical appliance design as they provide safety route during overvoltage faults. The soil (earth) been the universal ground is assumed to be at zero electric potential. However, due to properties like moisture, pH and available nutrients; the electric potential may fluctuate between positive and negative values that could be harmful for internally connected circuits on the grounding terminal. Fluctuations in soil properties may also lead to current crowding effect similar to those seen at the emitters of semiconductor transistors. In this work, soil samples are subjected to high impulse voltage discharge and the breakdown characteristics was profiled. The results from profiling discharge characteristics of soil in this work will contribute to the optimization of grounding protection system design in terms of electrode placement. This would also contribute to avoiding grounding electrode current crowding, ground potential rise fault and electromagnetic coupling faults.

Coherence and time-frequency analysis of impulse voltage and current measurements

The aim of this paper is to point out the advantages of the use of the time-frequency analysis in the digital processing of waveforms recorded in high voltage impulse tests. Impulse voltage tests are essential to inspect and test insulation integrity of high voltage apparatus. On the other hand, generated impulse currents are used for different test applications such as investigation of high current effects, electromagnetic interference (EMI) testing, etc. Obtained voltage and current waveforms usually have some sort of interferences originated from the different sources. These interferences have to be removed from the original impulse data in order to evaluate the waveform characteristics precisely. When the interference level is high enough, it might not be possible to distinguish signal parameters from the recorded data. Conventional filtering methods cannot be useful for some interference like white noise. In that case, time-frequency filtering methods might be necessary. In this study, the wavelet analysis, which is a powerful time-frequency signal processing tool, is used to recognize the noise of impulse current and voltage data. Thus, the noise sources can be determined by short time Fourier Transform, and a coherence approach is used to determine the bandwidth of noises.

Cold pressing of ferroelectric-ferromagnetic layered composites for nonlinear forming lines of high-voltage impulse generators

Cold pressing of ferroelectric-ferromagnetic layered composites for nonlinear forming lines of high-voltage impulse generators

One year of x-ray dosimetry in a high voltage laboratory

Reports of x-rays detection, produced by impulsive voltages in ordinary high voltage laboratories, can be found in the literature. These high voltages are very often to occur in the daily work of the laboratories around the world. This paper presents measurement results of x-ray dosimetry using thermo luminescent detectors (TLD) along 12 months of regular working in the High Voltage Laboratory of Institute of Energy and Environment (IEE) of the University of São Paulo (USP). Experimental tests applying high voltage impulses and placing TLDs in the vicinities of the electrode were performed and dosimetries in these conditions are also presented.

Laboratory demonstration of lightning strike pattern on different roof tops installed with Franklin Rods

Protection against lightning is always a challenging job for the researcher. The consequences due to lightning on different building shapes needs a comprehensive knowledge in order to provide the information to the common man. This paper is mainly concern with lightning pattern when it strikes on the building with different shape. The work is based on the practical experimental work in high voltage laboratory. Different shapes of the scaled structures have been selected in order to investigate the equal distribution of lightning voltage. The equal distribution of lightning voltage will provide the maximum probability of lightning strike on air terminal of the selected shapes. Building shapes have a very important role in lightning protection. The shapes of the roof tops have different geometry and the Franklin rod installation is also varies with changing the shape of the roof top. According to the ambient weather condition of Malaysia high voltage impulse is applied on the lightning rod installed on different geometrical shape. The equal distribution of high voltage impulse is obtained as the geometry of the scaled structure is identical and the air gap for all the tested object is kept the same. This equal distribution of the lightning voltage also proves that the probability of lightning strike is on the corner and the edges of the building structure.

「日本高電圧・インパルス試験所委員会」における高電圧測定の取り組み

1．はじめに

耐アーク試験時の過酷さに発弧用金属線が及ぼす影響評価

Metal wires are widely used for arc ignitions in power arc tests on electrical power installations, and their material and thickness are selected variously. However, the material and thickness of the metal wire are thought to be influential factors in the severity of the power arc test, because they may change the arc duration and the physical characteristics of arc. In this paper, we made the experiment, where arcs were generated in a closed chamber by two ignition methods. one was with using various metal wires for ignition, and another was without using them, namely with causing dielectric breakdown due to imposing the impulse high voltage. From the results, the difference of characteristics between arcs with and without using metal wires for ignition was investigated, focusing on the arc energy and the internal pressure rise, which can be seen as indexes of the severity of the power arc tests. Consequently, we pointed out that the severity of the power arc tests with using metal wires investigated in this study may be equal to or more than that of the tests with causing dielectric breakdown if there is little difference in the time integral of current during the arcing time.

Cavitation in liquid dielectric under nanosecond high-voltage impulse

We consider the appearance of a cavitation near a needle-shaped electrode under nanosecond high-voltage impulse. It was shown that the gas–liquid boundary moves in an opposite direction to the needle-shaped electrode under the influence of electric field on this boundary. It leads to an increase of the cavity volume. The comparison with experiment shows that the dependence of dielectric permeability on the electric field strength does not dramatically change the result of the numerical simulation whereas accounting for the liquid compressibility and the choice of the high-voltage electrode size are important. It was shown that the existence of the caviation bubbles do not always lead to electrical breakdown in dielectric liquid through the gas phase.