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The objective of this paper is to propose a method for quantitatively estimating the breakdown voltage of double short vacuum gaps in series under the lightning impulse voltage. The study found a quantitative relationship between the breakdown voltage and the maximum electric field strength at the cathode. This relationship is validated by previous experimental works when the total gap distance is less than 20 mm. [ABSTRACT FROM AUTHOR]

At present, the method of obtaining the voltage of transmission lines by using the inverse problem of the electric field is generally faced with the difficulties of solving data equations. Aiming at the above problems, the method that solves transmission wire voltage through spatial electric field integration based on D-dot sensor is proposed. In this paper, with the ground as the reference potential and the vertical line of the transmission line to the ground as the integral path, D-dot electric field sensor is applied to measure the instant electric field values of several nodes on the integral path and the transmission wire voltage is directly solved combined with Gauss–Legendre numerical integration algorithm. The Gauss–Legendre algorithm is verified by the electric field distribution data on the integration path obtained by simulation. Furthermore, the improvement of the Gauss–Legendre algorithm is realized through optimizing the integral interval so that the location of integral nodes is more reasonable. Finally, the measurement system based on LabVIEW is designed and the experiment platform of the analog transmission line is constructed. Experiment results show that the measurement method of transmission wire voltage through the improved Gauss–Legendre algorithm based on D-dot sensor owns high accuracy with an error of less than 1%. [ABSTRACT FROM AUTHOR]

Both Standards EN 50522 and IEEE 81 propose the fall of potential method (FPM) to carry out the measurement of the resistance to earth ($R_{\text{ES}}$) of an earthing system (ES). However, in urban areas, the recommended distances between the ES and auxiliary electrodes are not easy to respect, due to the presence of buildings and tarmac. Furthermore, unknown buried metallic parts and interconnections among ESs could modify the earth potential profile of the area, affecting the measurement results. In this paper, the key-issues that influence the measured $R_{\text{ES}}$ when the FPM is used in an urban environment are presented. A parametric analysis, carried out with Comsol Multiphysics, quantifies the errors due to wrong positioning of the auxiliary electrodes and due to the presence of interconnected ESs in the proximity of the ES under test. In addition, a real case of field measurement is described, emphasizing the main aspects that could compromise the results. Finally, practical suggestions to reduce errors are provided. [ABSTRACT FROM AUTHOR]

In urban and industrial areas, a relevant presence of buried metallic objects (e.g., gas and water pipes, etc.) can be detected. Usually, these elements are imagined as widespread meshed metallic grids in a good contact with the soil. In the last years, an arising interest on their role in the identification of a global earthing system has been expressed by the scientific community. Unfortunately, the geometrical and electrical properties of this kind of buried metallic parts cannot be provided by any documentations. This is mostly due to the fact that no trustworthy schemes are provided, as the management of these metallic parts is responsibility of different companies, which have installed them during several years. In order to characterize the buried metallic elements with reference to the electrical safety issue, the main quantity of interest is their resistance to earth. With this aim, a field measurement campaign was organized and the resistance to earth of more than 800 metallic objects has been evaluated through a simplified measurement protocol. In this paper, the measurement protocol, the setup, the results, and their analysis are reported. [ABSTRACT FROM PUBLISHER]

The payload of the four Cluster spacecraft dedicated to multipoint measurements in the earth’s magnetosphere includes ion emitters that can emit currents up to a few tens of microamperes to partially compensate for the photoemission current originating at the spacecraft surfaces and thereby achieve a reduction in the spacecraft potential from values often as high as several tens of volts positive to values well below 10 V. This effect is highly desirable to improve on-board particle measurements, especially of electrons, by reducing the photoelectron flux into the sensors and by reducing the distortions of particle trajectories in the spacecraft sheath. On the other hand, a perfectly stable spacecraft potential precludes the utilization of the spacecraft as a plasma probe, including the useful technique to estimate ambient plasma density from the spacecraft potential. This paper shows that the small residual variations of the potential still allow the determination of ambient plasma density, albeit at reduced accuracy. We present an outline of the applied method with examples. In spring 2002, in the cusp region, the Cluster interspacecraft distances were well below 1000 km. For selected intervals, the potentials of controlled and uncontrolled spacecraft are compared, taking advantage of the fact that the ion emitters were not operating on all spacecraft. Special considerations regarding the secondary electron production and its effect on the controlled spacecraft potential were found to be necessary, and examples of this aspect are presented as well. Finally, the effect of the potential control on the double-probe electric field measurements is assessed. It is found that the normal sun-aligned offset of the electric field caused by the asymmetric spatial distribution of photoelectrons around the spacecraft can be affected by the potential control. Nonetheless, the information about plasma density is not lost when active spacecraft potential control (ASPOC) is applied. This is also relevant for future missions with ASPOC, particularly the NASA Magnetospheric Multiscale mission launched in March 2015. Regular intercalibration of controlled and uncontrolled potentials is nonetheless advisable to increase the reliability of the method. [ABSTRACT FROM PUBLISHER]

An accurate model of nonlinear load is important for the evaluation of power quality (PQ). Among different PQ disturbance sources, alternating current electric arc furnace (AC EAF) is one of most complicated and serious loads. To provide effective operation prediction of AC EAF, a data-driven modeling approach based on time- and frequency-domain voltage-current (v -i) characterization is proposed in this paper. With the prediction of the proposed model in the time domain, the dynamic and short-term behavior of AC EAF can be observed. And the quasistationary and long-term features of AC EAF would be extracted via the frequency-domain phase of the proposed model. From the comparison on the field measurement data, the performance of the proposed model can be verified in the applications of PQ studies. [ABSTRACT FROM AUTHOR]

A method of predicting the residual breakdown electrical field strength of an epoxy-mica paper insulation system is described. This method was developed by using data on service?aged stator bars from generators as well as accelerated aging model bars. Thermal aging, mechanical aging, and combined thermal and mechanical aging were done individually as accelerated aging. The partial discharge characteristics, dissipation factor, and breakdown voltage were measured on the model bars and service?aged bars from generators. From these results, the residual breakdown electrical field strength was predicted based on the partial discharge characteristics and dissipation factor. First, the dominant type of deterioration (thermal or mechanical aging) on a bar?s insulation was determined by the pattern of voltage?partial discharge magnitude characteristics. Then the residual breakdown electrical field strength was predicted by using a predicting equation for both thermal and mechanical aging. Each predicting equation uses dissipation factor tip-up (i.e. difference in dissipation factor values between 2 kV and rated voltage) and partial discharge inception electrical field strength. The accuracy of this method was confirmed using data measured on 112 service-aged stator bars from generators and 10 accelerated aged model bars. The 95% confidence interval level included 94% of the measured residual breakdown electrical field strength values. This result shows that the method enables precise predictions of the residual breakdown electrical field strength of an epoxy-mica paper insulation system. [ABSTRACT FROM AUTHOR]

A methodology for extracting the lateral electric field ( \boldsymbol E\boldsymbol {x} ) in the drain extension of thin silicon-on-insulator high-voltage field-plate assisted reduced surface field (RESURF) devices is detailed including its limits and its accuracy. Analytical calculations and technology computer-aided design device modeling corresponding to experimental data are used. It is shown how to obtain trapped interface charge distributions (e.g., due to hot-carrier injection) from the extracted fields. Thus, a new method for determining the position and quantity of injected charges in the drain extension of RESURF power transistors is introduced. [ABSTRACT FROM AUTHOR]

Based on the similarity theory, a reduced-scale model is proposed to study the voltage distribution characteristics in ultrahighvoltage direct current converter transformer windings under the impulse voltage. Through comparing the distribution characteristics of electric field intensity and magnetic flux intensity of the scale model with that of the original model, the effectiveness of the reduced-scale method is verified. Furthermore, the actual production design is also considered in the model. The matrices of the inductance, capacitance, and resistance parameters for the reduced-scale model are obtained by finite element method. Then, the multi-conductor transmission line model is set up to study the propagation process of impulse voltage along the windings of the converter transformer. The voltage distribution curve is obtained under a standard lighting impulse voltage and the turn-to-turn fault is taken into consideration as well. The simulation results are the basis for the following experimental study. [ABSTRACT FROM AUTHOR]

The acceptability of pulsed electric field (PEF) processing as an alternative method for liquid food preservation requires the elimination, or at least the reduction, of all the effects accompanying the flow of electric current. Metallic particles might be released from the electrode material as a result of electrically driven electrochemical reactions. The presence of such metallic particles can affect the quality and the safety of PEF-processed food. This paper investigates the effect of varying the parameters of applied electric pulses on the amount of released metals, aiming to reach the optimum conditions. It is expected that reducing the rate of releasing metals from the electrodes will extend their lifetime and reduce the running cost of the PEF process. [ABSTRACT FROM PUBLISHER]