Impulse Voltage Generator Research Articles

Study on debugging of lightning impulse voltage waveform for large capacity ±800kV converter transformer in high altitude area

The Qinghai-Henan ±800kV UHV DC power transmission project is an UHV channel specially constructed for clean energy delivery, ±800kV converter transformers of the project are assembled and tested in Xining at an altitude of 2500 m, full-wave lightning impulse test is one of the main means to evaluate converter transformer insulation performance, its valve side lightning impulse voltage waveform parameters often fail to meet IEC60076-3 standards because of the large winding to the ground capacitance. In order to effectively assess the lightning tolerance of converter transformer, a simulation model of impulse test circuit of ±800kV converter transformer was built based on the existing 6000kV/560kJ impulse voltage generator and ATP-EMTP simulation software, three kinds of optimization methods are proposed, which include increasing the wavetail resistance, increasing load capacitor, and connecting the wave head in parallel with different inductors, the results show that the single optimization method can not meet the waveform requirements. Therefore, a combinatorial optimization test method of increasing the wavetail resistance and connecting the wave head in parallel with different inductors is proposed, which is completed and verified in the full-wave lightning impulse test on the valve side of Qinghai ±800kV high-end converter transformer, the results show that the optimized test waveform parameters meet the standard requirements.

Modernization of gas discharge visualization for application in medical diagnostics

The object of research is the processes of the emergence and glow of a discharge around biological structures in a pulsed electric field. Such processes have found use in the method of gas discharge visualization. In medical diagnostics, the general state of human health is assessed by the characteristics of gas-discharge images of fingers. One of the most problematic areas of the correctness of medical diagnostics is the dependence of the visual components of the image on the electrical characteristics of the discharge and the physical and chemical characteristics of the surrounding environment. In the course of the study, methods of modeling the electric discharge current circuit and electrical properties of biostructures were used. The proposed solution allows taking into account: the amplitude of the impulse voltage of the discharge, the frequency of the impulses, the duration and intensity of the impulses, the polarity, which act as additional diagnostic parameters of the gas-discharge visualization process. Physical processes are considered, and a model of a chain of gas discharge around a biological object in a pulsed electric field is proposed. It is shown that the occurrence of a discharge and the characteristics of the glow depend on the amplitude, duration, frequency, and polarity of the pulse voltage. These additional parameters determine the correctness of further visual diagnostics. Their quantitative measurement and the possibility of objective comparison should be attributed to the advantages of registering the proposed parameters of gas discharge visualization. The specified properties of these parameters provide an additional opportunity to digitally describe the condition of the object under study, and subsequently to automate diagnostics. The structural diagrams of the device for conducting research using the method of gas discharge visualization, the high-voltage impulse voltage generator unit for the hardware consideration of additional gas discharge parameters and their connection with medical and biological indicators have been developed. The use of the method and means of gas discharge visualization to assess the functional state of the flight crew in the pre- and post-flight period requires the development of special equipment. The proposed technical solutions require experimental verification. Comparative studies of diagnostic conclusions by the method of gas-discharge visualization with traditional medical diagnostics are necessary.

Solving EMC problems in the design of new HV test laboratory

The paper deals with solving electromagnetic compatibility (EMC) problems in the design of a new, case study, industrial high voltage test laboratory, intended to be used for testing of transformers and other apparatus up to 550 kV rated voltage. Modern high voltage test facilities are equipped, apart from primary test devices like AC, DC and impulse voltage generators etc., also with sophisticated numerical measuring instruments and informatics technology. Since such devices are sensitive to transient overvoltages, the highest degree of EMC is to be secured. This can be achieved by proper earthing and screening of test laboratory, what shall be designed in a way to satisfy all requirements conditioned by building lightning protection, personal protection and system earthing, avoiding electromagnetic compatibility disturbances at the same time. One of the main tasks is solving electromagnetic compatibility problems caused by outdoor electromagnetic disturbances originating from various unknown sources. Those disturbances and interferences may seriously influence measuring accuracy and readings of test devices, what consequently leads to false results. The stated is especially relating to partial discharge measurements. As to avoid such disturbances, the laboratory shall be completely screened with a net forming optimally designed Faraday cage. On the other hand, at high voltage tests with impulse voltages, especially with chopped tail waves, steep transient overvoltages may be generated. As a consequence, high transient potential differences between particular points along the earth electrode may occur, what can even lead to flashovers between parts of it. Therefore is of utmost importance to provide proper earthing and low inductance current return path for impulse high voltage test equipment where high frequency transients are to be anticipated. Improper earthing and bonding may result, apart from mentioned flashovers, in severe induced voltages in secondary cables with consequential influence on test results, possible destruction of measuring instruments and hazardous touch voltages for personnel. For analyzing transient potential differences, it is important to model, with maximum accuracy, impulse test circuit (impulse generator, chopping spark gap, voltage divider, Faraday cage, fundament earth electrode, earthing strips, earthing rods etc.). Magnitude of transient potential difference between particular points is proportional to earth electrode inductance, i.e. low inductance of earth electrode will result in decrease of transient potential difference.

Usage of high voltage impulse generator to research the process of electropulse destruction of locust larvae in the soil

In accordance with announced technology, a laboratory research complex is needed for researching the influence of electropulse effects on locust larvae (capsules) and identification of the processing modes and construction design required to cause their irreversible (fatal) damage. In this regard, a schematic diagram of a laboratory research complex for electropulse processing has been developed and its structure has been determined. A separate question concerned a source of high voltage and a shaper of high-voltage impulses. A special design of a high-voltage impulse generator has been developed. This design can produce impact impulses of various durations - the impulse duration depends on the capacitive storage; with maximum amplitude of 16 kV and current per impulse of up to 400 A. The generator uses a capacitive storage discharge through a thyratron controlled by a microcontroller to the load. The proposed high-voltage impulse generator is necessary for researching the effect of electropulse high-voltage technology on the irreversible damage of locust larvae located in the soil layer, and for the experimental identification of the operating modes of the electrical part of the designed electrotechnological system, which allows for destruction of locust capsules directly in the field. The designed high-voltage generator was tested in operational mode when working with a load, which was the soil volume placed between the electrodes in the working chamber. The shape of the operational impulse and its parameters comply with predefined characteristics for electropulse cultivation of soil massif with locust larvae (capsules). After the tests, minor structural adjustments were made, and the generator itself was prepared for experimental studies in the laboratory.

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.

Research on the Time-Domain Dielectric Response of Multiple Impulse Voltage Aging Oil-Film Dielectrics

Power capacitors suffer multiple impulse voltages during their lifetime. With the multiple impulse voltage aging, the internal insulation, oil-film dielectric may deteriorate and even fail in the early stage, which is called accumulative effect. Hence, the time-domain dielectric response of oil-film dielectric with multiple impulse voltage aging is studied in this paper. At first, the procedure of the preparation of the tested samples were introduced. Secondly, an aging platform, impulse voltage generator was built to test the accumulative effect of capacitor under multiple impulse voltage. Then, a device was used to test the time-domain dielectric response (polarization depolarization current, PDC) of oil-film dielectric in different aging states. And finally, according to the PDC data, extended Debye model and characteristic parameters were obtained by matrix pencil algorithm identification. The results indicated that with the increase of impulse voltage times, the time-domain dielectric response of oil-film dielectric changed accordingly. The polarization current curve moved up gradually, the insulation resistance decreased when subjected to the repeated impulses. In frequency domain, the frequency spectrum of tan δ changed along with the impulse accumulation aging, especially at low frequency. At last, combined with the aging mechanism of oil-film dielectric under multiple impulse voltage, the test results were discussed.

Design of 4-stage Marx generator using gas discharge tube

In this paper, a Marx generator voltage multiplier as an impulse generator made of multi-stage resistors and capacitors to generate a high voltage is proposed. In order to generate a high voltage pulse, a number of capacitors are connected in parallel to charge up during on time and then in series to generate higher voltage during off period. In this research, a 6kV Marx generator voltage multiplier is designed using gas discharge tube (GDT) as an electronic switch to breakdown voltage. The Marx generator circuit is designed to charge the storage capacitor for high impulse voltage and current generator applications. According to IEC 61000-4-5 class 4 standards, the storage capacitor must be charged up to 4 kV. The results show that the proposed Marx generator can produce voltages up to 6.8 kV. However, the storage capacitor could be charged up to 1 kV, instead of 4 kV in the standard. That is because the output impulse voltage has narrow time period.

Simulation and Experimental Analysis of an Impulse Voltage Generator

This paper presents the simulation and experimental analysis of an impulse voltage generator (IVG) used for atmospheric discharge voltage tests. The electrical equivalent circuit of the IVG was simulated using the electromagnetic transients program EMTP-VR. Besides the simulation of the generator operation, it was necessary to make a detailed revision of the IVG components and determine their working condition to carry the laboratory experiments. The lack of a high DC voltage source to feed the IVG led to developing a high-voltage dc supply. Although the IVG was designed and built in February 1982, this equipment was out of operation due to its DC power supply failure. Due to the interest in rehabilitating the equipment to perform high voltage experiments, and with the need to characterize insulation materials and electrical equipment subject to electrical stress, it was decided to put it back into operation. Capacitor tests were carried out for each IVG stage to determine if they fulfilled the electrical charging function. Other components were also repaired, such as damaged resistances and sphere gaps. The impulse generator was configured with a maximum of six stages which is half of the original design. Before doing an experiment with the IVG, a simulation analysis was made to study the IVG. The simulation results allow evaluating before the experimentation whether the impulse generator is working correctly; the model allows to analyze the charge and discharge of each capacitor and the electrical currents at each branch of the IVG equivalent circuit. Performance Simulation and experimental results are presented to demonstrate the IVG functionality. The IVG will be used for carrying out insulation tests made by power engineering graduate students.

Measurements of radiation induced by a spark discharge under laboratory conditions

Terrestrial gamma and neutron flashes can result in considerable radiation exposure of aircraft crew and passengers in their close vicinity. Lightning impulse voltage generators imitate selected stages of natural lightning processes and can serve as a test environment for the development and calibration of detector systems for such short term radiation events. This work presents the results of measurements of absorbed dose using thermoluminescent dosimeters for 400 negative discharges at the lightning impulse voltage generator. The thermoluminescent dosimeter CaSO4:Dy and the combination of lithium-fluoride detectors MTS–6, MTS–7, and MTS–N were used to quantify the photon and neutron components of the radiation field. The detectors were placed in four positions near the generator spark gap. The results confirm the presence of thermal neutrons and photon radiation in two positions at the lightning impulse voltage generator.

Experimental analysis of artificial lightning breakdown and ignition characteristics in grassland

Lightning fire is an important influencing factor of grassland ecology. It is one of the important ignition sources of grassland fire. The previous researches on lightning fires were mainly focused on forests, but researches on grassland were insufficient. In this paper, the impulse voltage generator was used to evaluate the breakdown characteristics of grass bed. The relationship of breakdown voltage to moisture content and bulk density was obtained. Based on the impulse current generator, an artificial lightning ignition prediction model of impulse current was derived. Results show that the breakdown voltage of grass bed decreases rapidly with the increase of moisture content. With the increase of peak current, the total lightning energy increases, while the heating efficiency decreases.

Proposal of New Base Curve for IEC 60060-1 and Compensated Impulse Voltage Generator's Waveform Parameters

Proposal of New Base Curve for IEC 60060-1 and Compensated Impulse Voltage Generator's Waveform Parameters

Stimulatory growth effect of lightning strikes applied in the vicinity of shiitake mushroom bed logs

Since ancient times, the anomalous occurrence of mushrooms has been observed in and around locations struck by lightning. Based on this phenomenon, various cultivation techniques using a high voltage to cultivate shiitake mushroom in bed log (wood) have been proposed. Undoubtedly, the fruiting capacity of shiitake mushrooms is significantly promoted by direct application of a high voltage to the cultivation bed logs. However, mushroom bed logs are rarely struck directly by lightning in the natural environment. Thus, it is important to devise a stimulation method that matches conditions in the natural environment. In this study, we performed experiments involving indirect lightning strikes using a new method that mimics the natural environment as closely as possible. Specifically, we used the electric discharge created by an impulse voltage generator to create lightning but did not apply it directly to the cultivation bed log. Instead, the cultivation bed logs were placed a few meters away from the lightning rod. Subsequently, the fruiting capacity of the shiitake mushrooms with and without the indirect lightning strikes was compared. The experimental results indicated that, with the indirect lightning strikes, the extent of shiitake fruiting almost doubled compared to the case without the indirect lightning strikes. Furthermore, the results confirm that an increased shiitake mushroom production is possible using lightning strikes, even if the associated high voltages are not applied directly to the bed logs.

Lightning attachment behavior of wind turbine generator with blades equipped with two lightning receptors

Lightning striking of wind turbine generators (WTGs) has taken place frequently in recent years and usually results in severe blade damages. In order to study the lightning attachment behavior of the WTG, a scaled‐down model with a ratio of 1:100 was assembled to simulate a 2 MW‐class wind turbine for which each blade is equipped with two pairs of lightning receptors. In order to simulate the lightning strikes from different directions, the high‐voltage rod electrode was repositioned at 29 orientations with respect to the WTG model, and by energizing the rod electrode via an impulse voltage generator, which can generate the switching impulse voltage and the lightning impulse voltage, the negative and positive impulses were generated. Obtained results show that the negative impulses tend to be intercepted by the blade‐tip receptor, whereas the positive ones are also likely to attach to the insulation parts of blade and the nacelle. Moreover, the switching impulse is prone to being intercepted by the insulation parts of blade, more distinctly than that in the case of lightning impulse. The interception efficiency of the WTG model, represented by the ratio of number of discharges intercepted by blade receptors and lightning rod against the total applied strikes, is larger in the case of negative impulse than that of the positive impulse. Our test results show important implications for the phenomenon of lightning damage and the attachment behavior of WTGs affected by lightning polarity and waveform. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Study on Influence Factors of Lightning Impulse Test Waveform of UHV GIS Equipment

The lightning impulse withstand voltage test is a test item that must be carried out for type testing, factory test or even field test of electrical equipment such as gas insulated metal-enclosed switchgear (GIS).However, the factors affecting the lightning impulse test waveform are complex and diverse. In this paper, the discharge principle of the impulse voltage generator is studied. Combined with simulation, the influence of different factors on the waveform parameters of lightning impulse test of UHV GIS equipment is obtained. The common methods and improvement measures of waveform debugging are pointed out, and the main factors affecting the parameters of lightning waves are studied.

Measurement of the voltage distributions over transformer winding in standard lightning impulse voltage

This paper mainly focuses on the distribution of the standard lightning impulse (LI) voltage over transformer windings. In order to obtain the voltage waveform of different windings, the test platform contains an impulse voltage generator and a 35kV transformer model with multiple winding taps is built. Results of the distribution voltage are provided. The lightning impulse voltage distributes in a nonlinear way. The distort waveforms show the internal oscillations of the winding and resonant frequencies are in the range of several hundreds of kilohertz. The voltage difference between windings is larger in some specific windings, which gives some references for interturn insulation design.

Development of an innovative repetitive impulse voltage generator [News from Japan

It is well recognized that our modern world would not be so developed without the advancement of power electronics. Almost all electrical and electronic machines use various power electronic technologies. Among many power electronic devices or systems, the contribution of a converter–inverter system is most significant. Here, converters are the devices that convert AC voltages to DC voltages, and inverters convert them in the opposite way. Electric power conversion devices that use both converters and inverters are often called “converters,” although they are usually called “inverters” in Japan. We can say that all electronic devices require converters. In addition, converters can significantly increase the efficiency of a driving system using electric motors. A typical example, Tokyo Metro Co. Ltd. and Mitsubishi Electric Corporation, both in Tokyo, announced that they achieved the reduction of electric power consumption of commuter subway trains by 38.6% by introducing SiC-based pulse-wave-modulation converters in 2012 [1].

Experimental evaluation of discharge characteristics in inhomogeneous fields under air flow

The impact of high velocity air flow on discharge characteristics generated in strongly inhomogeneous electrical fields has been investigated under DC and combined DC + impulse voltages. In the laboratory, a needle plane electrode configuration with a gap distance of 20 cm was exposed to high voltages and a laminar air flow up to 22 m/s. In the first setup, the gap was exposed to a variable DC potential of up to 100 kV in order to create space charges in the vicinity of the electrode. The impact of the air flow on partial discharges and the dynamic behavior of the space charges is evaluated by means of partial discharge measurement and ultraviolet photography. The results show that the air flow increases the frequency of partial discharges in the gap due to an increased rate of space charge removal in the high field area around the tip of the electrode. The partial discharge behavior shows higher dependency on air flow at positive tip polarity as compared to the negative polarity. In the second setup, the standard impulse voltage created by a multistage impulse voltage generator was superimposed to a DC voltage, which continuously created corona and space charges around the tip of the electrode. Breakdown of the gap was triggered by means of the impulse voltage. The DC offset was varied from 0 kV to 100 kV in 20 kV steps and the 50 % flashover voltage was determined for both polarities. The results show that the impact of the air flow is highest at negative DC potential with negative impulse voltage, with an increase in flashover voltage of 40 % when air flow is applied. At positive polarity, the impact of air flow is only observable at 100 kV when the wind extinguishes the stable streamer stem.

Applications of impulse current and voltage generators dedicated to lightning tests of avionics

Applications of impulse current and voltage generators dedicated to lightning tests of avionics

Measurement of the electric field strength in transformer oil under impulse voltage

The electric field distribution of the oil-pressboard structure under impulse voltage provides vital reference for the design of transformer insulation. The electric field distribution under impulse voltage is usually held equivalent to that of the capacitive field and calculated by simulation software. An appropriate margin to the calculation results is then selected according to the allowable strength. The design value identified in such a manner, however, falls short of support and verification of actual measurement. The present paper proposes a non-contact real-time measuring method to explore the electric field distribution of the oil-pressboard structure under impulse voltage, using a created measuring apparatus that is composed of optical system, photoelectric converter device, sealed cavity, and impulse voltage generator. Calibrated and verified by a pair of plate electrodes which generated uniform electric field along the propagating direction of the laser beam, the measured values proved to tally well with the actual values of the electric field in terms of both variation trend and numerical value. The minimum sensitivity of the established measuring apparatus was recorded as 3.5 kV/mm and the maximum deviation was 3.6%.

Design and Fabrication of a High Voltage Lightning Impulse Generator

This paper reports 10 kV to 100 kV high voltage impulse generator. Generation of variable outputs impulse generator can be designed by combination of flyback transformer and Marx generator which can produce different high voltages. It is a portable device for field. The experimental final results have been taken by using spark gap measurements and voltage divider technique. This high voltage lightning impulse generator produces standard T1/T2 waveshape impulses. The testing of protection devices such as SPD (surge protection device) is extremely important to find out whether these devices can operate in standard conditions or not. That’s why the high voltage lightning impulse generator is developed for such testing. Similarly, our research work consists of modeling and practical design of a 100 kV impulse generator.