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Although vacuum technology is commonly used in power systems, challenges still remain for vacuum circuit breakers (VCBs) to cope with the requirements of capacitor bank switching duties as the insulation performance can deteriorate by inrush current. In order to reduce the restrike probability, vacuum interrupters (VIs) in series are recommended. The objective of this paper is to investigate the field emission current I e characteristics and voltage distribution in series vacuum gaps after making inrush current. The results show that I e of the VI pre-stressed by inrush current is much higher than that of the new one and I e has a conditioning effect. It is found that the insulation performance of two pre-stressed VIs in series is not significantly improved compared to a single VI. But the insulation performance of a new VI and a pre-stressed VI in series is significantly improved. Moreover, the voltage distribution of two VIs in series can be estimated by I e. It is found that each VI only withstands about 50% of the applied voltage when two pre-stressed VIs are in series. However, the new VI can withstand >70% of the applied voltage when a new and a pre-stressed VI are in series. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate the effect of a high-frequency high-voltage impulse conditioning technique on the inrush current interruption phenomena. In this paper, the inrush current interruption phenomena referred to the actual interruption and the currentless period following interruption. First, Six 7.2 kV vacuum interrupters (VIs) were conditioned by 400 batches of voltage impulses. The duration of each batch were set to 0.1 s. The peak value of each impulse could reach up to 100 kV. The repetition frequency of the impulse was set to 1000 Hz. The contact gap was 0.8 mm. The VIs were tested for the inrush current interruption performance with inrush current set to 2 kA and 5 kA, with a frequency of about 3800 Hz. The experimental results showed that there were two different types of inrush current interruption depending on high-frequency high-voltage impulse conditioning. The inrush current interruption type I referred to the inrush current interruption during the prestrike process before the contacts touched. This type inrush current interruption could be caused by the erosion of prestrike arc. Moreover, the high frequency voltage impulse conditioning influenced the occurrence frequency, the number of interruptions and the duration of the inrush current interruption type I. The inrush current interruption type II referred to the inrush current interruption during the contact bouncing process after the contacts touched. The inrush current interruption type II occurred only in the case of the VIs after conditioning. Furthermore, the occurrence frequency of the inrush current type II decreased with increasing inrush current. [ABSTRACT FROM AUTHOR]

The fracture behavior of metallized electrode (ME) under pulsed current with current density of 1011∼1012 A/m2 and pulse with width of microseconds is studied in this paper. High-speed camera is applied to record the surface state of metallized electrode. Based on photos of the surface state and waveforms of the current and voltage, the fracture behavior under the stages of melting, liquefaction, vaporization and plasma are acquired. The process of the exploding phenomenon is discussed in detail. The photos show that the fracture direction is perpendicular to the current. Joule heating and electromagnetic force is the reason for the development direction of the fracture. The influencing factors of electric explosion are experimentally analyzed. Results indicate that the specific action integral (h) can not be considered as a constant. The specific action integral (h) and energy transfer efficiency (?) will decrease with the increasing of di/dt (ratio of peak current value to peak time) and current density (j). The energy transfer efficiency (?) increases from 36% to 71% when the current density ranges from 2.3?1011 A/m2 to 1.1?1011 A/m2, which means the threshold value of electric explosion of 5 nm ME is closely to 1?1011 A/m2. The research results indicate that the high current density (1011~1012 A/m2) and high di/dt may lead to the electrode fracture in the metallized film capacitor. The safe-use current density of capacitors must be below 1?1011 A/m2. [ABSTRACT FROM AUTHOR]

This paper proposes a novel topological solution for pulsed power converters based on capacitor-discharge topologies, integrating a Fast Voltage Compensator which allows an operation at constant power consumption from the utility grid. This solution has been retained as a possible candidate for the CLIC project under study at CERN, which requires more than a thousand synchronously-operated klystron modulators producing a total pulsed power of almost 40 GW. The proposed Fast Voltage Compensator is integrated in the modulator such that it only has to treat the capacitor charger current and a fraction of the charging voltage, meaning that its dimensioning power and cost are minimized. This topology can be used to improve the AC power quality of any pulsed converters based on capacitor-discharge concept. A prototype has been built and exploited to validate the operating principle and demonstrate the benefits of the proposed solution. [ABSTRACT FROM PUBLISHER]

This paper describes the implementation of a load voltage observer into the control algorithms of a Rapid Capacitor Charger controlled by a digital signal controller (DSC) with a fast DSP core. A hybrid peak current mode control algorithm with digital control of the PWM signal and high speed analog current sensing is used to control the inverter of the charger. The DSC controller keeps the current loop stable using adaptive slope compensation. In addition to providing fast adaptive digital control of the current loop, the DSC can perform additional functions such as estimation of the voltage level of the load capacitor. This avoids the cost, bandwidth limitations and insulation challenges of a conventional HV-sensor. To evaluate the performance of the load voltage observer, we measured the output voltage with a laboratory grade HV probe to establish a reference to test the results of the digital algorithm. [ABSTRACT FROM PUBLISHER]

When the metallized polypropylene film capacitor (MPPFC) is used under high electric field in pulsed power systems, an obvious voltage decay phenomenon will occur. The voltage decay is mainly resulted from the relaxation polarization in dielectric applied under high electric field. This paper focuses on the relaxation polarization in metallized biaxially oriented polypropylene (BOPP) film capacitors. The extended Debye model of relaxation polarization is discussed and the parameters of each RC branch are obtained. Meanwhile, the relationship between the increasing proportion of polarization charge (ΔQa/Qh) and temperature is investigated. The experimental results show that under 1kV, ΔQa/Qh varies from 0.018 to 6.868 with the temperature varing from 10 to 70 /spl deg. Moreover, the equivalent capacitance of capacitors in frequency domain is analyzed with consideration of slow polarization. The analysis shows that both a lower frequency and a higher temperature can accelerate the relaxation polarization and increase the voltage decay. Based on the extended Debye model developed from the polarization charge test, the voltage drop is calculated and the results can match well with those of the voltage maintaining test. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate an impact of the inrush current on the prestrike and restrike characteristics of vacuum interrupters (VIs) during capacitive current switching duty. Eleven 7.2 kV VIs are used. Their contact parameters are contact gap 4 mm and contact material CuCr25 (25%weight of Cr). A series of 80 CO operations are executed for each test VI. The amplitude of inrush current Iinrush (3800 Hz) is set to 0 kA, 2 kA, 5 kA and 10 kA, respectively. The switching current is less than 1 A rms. The (1-cosωt) shape of the recovery voltage with a peak of 15 kV is applied to the test VI. The experimental results show that the prestrike and restrike phenomena are significantly influenced by the contact surface conditions damaged by the inrush current. The cumulative probability of the prestrike gap dpre follows a 3- parameter Weibull distribution. When Iinrush increases from 2 kA to 5 kA, the prestrike gap increases accordingly. The 10% dpre increases from 0.5 mm to 0.7 mm. The 50% dpre increases from 0.7 mm to 1.0 mm. The 90% dpre increases from 1.0 mm to 1.5 mm. The scale in the Weibull distribution, which can describe the scattering of dpre, is 0.2 mm and 0.6 mm in the case of Iinrush = 2 kA and Iinrush = 5 kA, respectively. It is found that the occurrence frequency of the inrush current interruption increases from 37.9% to 68.3% with the increase of Iinrush from 2 kA to 5 kA. Moreover, the inrush current also has an impact on the restrike types, which are classified into three types according to the waveform features. The average restrike probability increases from 4.6% to 17.9% and further to 30.4% with the increase of the inrush current from 0 kA to 2 kA and 5 kA, respectively. In addition, the higher the inrush current, the restrike tends to occur earlier during the recovery voltage period. [ABSTRACT FROM AUTHOR]

Iron-based nanocrystalline ribbon has been widely used in pulsed power devices such as transformer, magnetic switch and linear transformer driver, due to its fast response to the high-frequency pulse, high permeability and low loss of magnetization. In this paper, the ns- and μs-range insulation characteristics of iron-based nanocrystalline ribbon coated by TiO2 film with μm-range thickness are studied in detail. In order to evaluate the induced inter lamina voltage of the stacked ribbons, a method for withstand voltage test of the nanocrystalline ribbon is put forward under short voltage pulses. In air and transformer oil, breakdown voltages of the nanocrystalline ribbons were investigated under the conditions of different pulse widths and repetition rates. Breakdown voltages of multiple layers of the ribbon samples in stacked were also studied, and many important conclusions were revealed. The conclusions show great value on the design and manufacture of the magnetic pulsed power devices at the range of several hundred kV. [ABSTRACT FROM AUTHOR]

Capacitor charging power supply (CCPS) is one of the most important components of a pulsed power system. The CCPS studied in this paper is used in power conditioning systems for Laser Nuclear Fusion. With a view to enabling multiple CCPSs to work concurrently in an environment of high voltage, high power and strong electromagnetism, this paper carries out a profound and systematic research into the characteristics of a capacitor charging power supply, including charging rate, harmonic features, efficiency and voltage precision, etc. Furthermore, some measures to improve the characteristics of CCPS are put forward. The advantages of high charging rate, low harmonic, high efficiency and accurate charging voltage are proved by the results of experiments and the performance in practical operation on a 23.5 kV, 50 kW, 4400 μF CCPS. [ABSTRACT FROM AUTHOR]

The presence of partial discharges is one of the most prominent indicators of defects and ongoing degradation processes of electrical insulation. As a high percentage of failures are associated with partial discharges, the need for the classification, extraction and evaluation of partial discharge signals is essential. Consequently, an electrical model of a breakdown void, modeled as part of the power system, is more than a necessity. In this paper an improved capacitive model of void based on streamer concepts is proposed for the study of the transients generated at the void location. Further, the high frequency model of the cable is employed in order to examine the propagated partial discharge simulated transients of the improved capacitive model. The simulated transients of both models are compared and discussed on a theoretical basis. [ABSTRACT FROM PUBLISHER]

In this paper athree-stage pulse generator architecture capable of generating high voltage, high current pulses is reported and system issues are presented. Design choices and system dynamics are explained both qualitatively and quantitatively with discussion sections followed by the presentation of closed-form expressions and numerical analysis that provide insight into the system?s operation. Analysis targeted at optimizing performance focuses on diode opening switch pumping, energy efficiency, and compensation of parasitic reactances. A compact system based on these design guidelines has been built to output 8 kV, 5 ns pulses into 50 ?. Output risetimes below 1 ns have been achieved using two different compression techniques. At only 1.5 kg, this light and compact system shows promise for a variety of pulsed power applications requiring the long lifetime, low jitter performance of a solid state pulse generator that can produce fast, high voltage pulses at high repetition rates. [ABSTRACT FROM AUTHOR]

This paper presents a novel topology for the generation of high voltage pulses that uses both slow and fast solid-state power switches. This topology includes diode-capacitor units in parallel with commutation circuits connected to a positive buck-boost converter. This enables the generation of a range of high output voltages with a given number of capacitors. The advantages of this topology are the use of slow switches and a reduced number of diodes in comparison with conventional Marx generator. Simulations performed for single and repetitive pulse generation and experimental tests of a prototype hardware verify the proposed topology. [ABSTRACT FROM AUTHOR]

This paper describes the operation of a solid-state series stacked topology used as a serial and parallel switch in pulsed power applications. The proposed circuit, developed from the Marx generator concept, balances the voltage stress on each series stacked semiconductor, distributing the total voltage evenly. Experimental results from a 10 kV laboratory series stacked switch, using 1200 V semiconductors in a ten stages solid-state series stacked circuit, are reported and discussed, considering resistive, capacitive and inductive type loads for high and low duty factor voltage pulse operation. [ABSTRACT FROM AUTHOR]