Search

In a Tesla-type pulse generator, self-inductance of the primary coil is a crucial parameter to determine the final oscillating condition. However, the accurate value of this inductance might be changed due to the uneven primary current distribution caused by practical configuration of the primary side. Consequently, in order to precisely design the transformer, it is helpful to evaluate the primary inductance based on electromagnetic simulation instead of conventional approximate calculation. In this paper, a simulation model based on the finite integration technique is established to solve the uneven primary current problem. A primary coil with multiple contacting points is designed, and hexahedral mesh generation of the coil is also discussed. Hence, a series of verification tests using different primary structures are performed to support the results of simulation. Both results of the simulation model and the verification test presented that the variation of the primary inductance will affect the performance of the generator, and the number of contacting points is the main cause to determine the maximum current density of the coil. [ABSTRACT FROM AUTHOR]

Calculation of geomagnetically induced current (GIC) flowing through power system during the geomagnetic storm has attracted more attention recently. However, for high voltage power systems with transmission lines over hundreds or even thousands of kilometers, the earth model and geomagnetical field generally vary significantly. So, it is essential to take them into consideration using limited earth survey sites and geomagnetic observatories. To address this problem, a Kriging method is introduced in this paper to make earth model and geomagnetical field interpolations. It has the characteristic of spatial autocorrelation by considering not only the distances between predicted points and training points but also the distances between training points themselves. Finally, a case study of the Central China 1000 kV ultra-high voltage (UHV) grid is carried out to illustrate the applicability and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this article, a nonparametric vulnerability assessment method is proposed for the equipment excited by transient electromagnetic disturbances. By carrying out the proposed method, the probability distributions of multistate failure thresholds could be obtained for the cases of lacking prior knowledge, such as the effect mechanism, related distribution characteristics and training data. In fact, the proposed method combines support vector machine (SVM) and Gaussian process regression (GPR). SVM may extract the classification hyperplane from a small number of test samples, and obtain the continuous classification indicators subsequently. Furthermore, the regression results of classification indicators based on GPR can provide both mean values and their confidence intervals. To deal with the multilevel effect assessment, the “one against the rest” strategy is applied and probabilities of each level can be assessed simultaneously. Finally, a case study of an electronic system is carried out to illustrate the applicability and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

A Tesla transformer with duplex winding is designed. The secondary winding of the transformer is divided into two parts, a 120-turn tapered winding and a 6-turn extra winding, which combine the transient oscillation of the main tapered winding and the main gap's trigger electrode. This configuration improves the performance of the main gap and makes the generator more compact. Two types of numerical techniques are introduced: a time-dependent finite element method model and a double transmission line lumped circuit model. To validate these models, calculated voltage signals on the extra winding are compared with the measured signal. The verification test shows that results of the two models are acceptable. Errors between the measured signal and simulation results are explained. [ABSTRACT FROM AUTHOR]

For typical Tesla transformers with open magnetic-core, a novel coaxial design of the primary side using a mechanically controlled spark gap is introduced to obtain a more compact configuration. The primary winding has several alternative ports to vary the current distribution by changing the position of the capacitor component, and the entire primary circuit is built inside the outer cylinder. For this new primary configuration, we estimate the series parameters and ohmic losses: Polypropylene film capacitors and combined metallized film capacitors are used in the verification tests, and the former capacitor exhibits a lower parasitic resistance below 10 mΩ. The ohmic losses caused by the windings and spark gap are also considered. The results of the experiments show that the voltage gain has an 8.2% drop when the parasitic resistance of C1 increased from 10 mΩ to 24 mΩ, and we deduce that the contact resistance of this primary structure can be limited to below 10 mΩ according to the circuit analysis results and the verification test. [ABSTRACT FROM AUTHOR]

This paper illustrates the formation of a volume pulsed glow discharge in air stressed by a single pulse with tens of nanosecond rise time in a nonuniform electric field gap. The images presented here show that diffuse discharges can be obtained in air with no filamentation at different pressures. With the increase of air pressure, the transform appears from diffuse discharge channels to discrete discharge channels because of the inhibiting effect of electron avalanches. Index Terms--Gas pressure, glow discharges, pulsed discharge.

The lightning electromagnetic field which illuminated the overhead line is the nonuniform field. When analyzing the lightning induced overvoltages on overhead lines by in frequency domain, to get an accurate response, the observation points of the horizontal electric field along the overhead line should be as many as possible. However, the expression of the horizontal electric field is formulated in the integral form and should be solved by the time-consuming numerical integration process at every observation point, which leads to a low calculation efficiency. This paper proposes an efficient method to avoid the numerical integration process at all the observation points and to enhance the calculation efficiency. In this method, the horizontal electric field at a few observation points along the line are calculated in the numerical way first, then the amplitudes and phases of the horizontal electric field along the line are fitted separately at every frequency with the fitting functions of the position $x$ along the line. The amplitudes are fitted by the Fourier series, and the phases are fitted by the polynomial functions. Based on the obtained analytical fitting representations, the transmission line response could be solved efficiently. The two different lightning electromagnetic pulse (LEMP) validation examples show the validity and general applicability of the proposed method. [ABSTRACT FROM PUBLISHER]

With the rapid developments in pulse power technology, the gas spark switch has broadened its application in both industrial fields and research fields, such as the extraction of unconventional gas resources and underwater electrical wire explosion. Thus, the repetitive switch needs high current capability, small breakdown voltage variance, and long lifetime in an airtight cavity. The performances of the switch directly influence the output characteristics of the system, but electrode erosion is inevitable, which may decrease the self-breakdown voltage and the lifetime. The purpose of this paper was to investigate the electrode erosion characteristics under adverse conditions. The cathode showed a worse erosion surface. Compared with the central zone of the electrodes, the outer zone showed a worse surface roughness for both the cathode and the anode. [ABSTRACT FROM PUBLISHER]

Self-integrating Rogowski coil has been widely used for measurements of pulsed currents from nanosecond timescale to microsecond timescale in pulsed power systems. Appropriate designs of coil’s structure are vital to high-frequency response. This paper proposed a new structure of Rogowski coil so as to provide a better response to fast pulsed current. Four Rogowski coils with different structures were tested in three different platforms. Experimental results showed that the hybrid Printed Circuit Board Rogowski coil had the best performance in this paper, which could respond to square waves with fronts of $\sim 2$ ns and had a sensitivity of 0.585 V/kA. The designed maximal peak current was 100 kA. [ABSTRACT FROM PUBLISHER]

In order to solve many problems occurred in the initial development period of the new coal reservoir fracturing and permeability improvement technology with high accumulated energy electric impulse stress wave, the electric impulse stress wave loading experiment and micro-location observation means were applied to the study on the micro crack occurred development process of the fat coal sample from Ordos Basin and the influence factors. The results showed that in the repeated electric impulse stress loading experiment, with the impact number increased, the micro crack line density would be increased and the formation of the new generated micro crack would come from the shearing stress occurred by the impact wave. The stress failure process of coal could be divided to three stages generally. The micro crack network of coal would be basically formed when the coal was impacted fourthly, there would be no coal cuttings occurred obviously, so impacted fourthly was the best condition. The micro crack network of coal would be mainly developed in the vitrinite band, new generated micro cracks would have a priority to start the expansion in the large size original structural defects. The electric impulse stress wave would have obvious fracturing and permeability effect of the coal and the original structural defects existed in the coal would be main part to have the coal micro cracks. The coal and rick bands type and other combined mode would be the important geological factor considered to set up the coal reservoir permeability improvement and reconstruction measures. [ABSTRACT FROM AUTHOR]

A coal reservoir excitation by the repeated strong pulse waves of high energy accumulation was an originality new technology developed by Chinese scientists based on the principle of the nuclear explosion shock wave. The discovery of the preliminary work showed the permeability improved feasibility and availability of the coal reservoir. But the basis study lagged behind the engineering discovery and the further research and development and the promoted application of the technology were urgently needed to make a breakthrough at the bottleneck of the basis study. Faced to the major technical requirement of the high efficient economic development of the coalbed methane in China, the paper analyzed the study status on the shock wave fracturing and permeability improved field of the coal reservoir, stated the basic principle of the coal reservoir fracturing and permeability improved with the repeated strong pulse wave of the high energy accumulation, summarized the preliminary site experiment of the technology and the engineering discovery effect, and refined the scientific problems to be solved along the direction. The paper discussed the breaking dynamics features of the coal reservoir and the coupling role mechanism of the geological and engineering factors under the guidance of the repeated strong pulse waves of the high energy accumulation, in detail explained the key scientific problem of the wave-flow-coal interreaction under the guidance of the repeated pulse waves, which would be the most important basis to further research and development and to improve and apply the permeability improved technology of the coal reservoir. [ABSTRACT FROM AUTHOR]

X-pinch experiments have been carried out on a 100 kA, 100 ns linear transformer driver stage recently built up. The X-pinches exhibited a source size of about 10 μm, a pulse duration of 3 ns, 3-5 keV radiation energy of 3.9 mJ, and a burst time jitter of tens of nanosecond with the 2-wire 8 μm W X-pinch load. The generator output current and the X-pinch characteristics depended on the X-pinch wire materials in the tests. X-ray backlighting images from the insects showed the significant phase-contrast effect. [ABSTRACT FROM AUTHOR]

In pulsed power systems, pulsed currents with risetimes from nanosecond to microsecond can be effectively measured by self-integrating Rogowski coils. Appropriate design of the structure and the integrating resistor is crucial to the high-frequency response of a coil. In this paper, several novel designs of Rogowski coil's integrating resistors were proposed and tested. Experimental results showed that the optimized coil could response square waves with fronts of ∼1.5 ns and had a sensitivity of ∼0.75 V/kA. The maximal peak current was designed as 100 kA.