In order to further improve the output voltage amplitude and repetitive operation reliability of nanosecond pulse generator (PG) based on avalanche transistor (AT), the method of power synthesis of modularized Marx circuits with transmission line transformer (TLT) is employed in this article. The modified positive $4\times11$ -stage Marx circuit introducing base-triggering method is designed and implemented to improve the operation reliability. The triggering synchronization and the consistence of output characteristics of multiple Marx modules with an identical trigger pulse are validated. The feasibility of combining pulses generated from four Marx modules with an optimized four-stage TLT is demonstrated. The influences of the type and quantity of magnetic core and the superimposed stage number of TLT on the output performance of the generator are investigated. The operation characteristics of the generator including output parameters, trigger time-delay, and loop efficiency in the whole working range are evaluated. The experimental results show that the working range of the overall device has been widened significantly with the injection of additional initial carrier. Accordingly, the generator prototype is capable of achieving the output performance with an adjustable voltage amplitude in the range of 7.8–26.7 kV on a matched 300- $\Omega $ resistive load and 12.2–38.9 kV on the high-resistance load, respectively, a 10%–90% rise time of 3.6 ns, and a full-width at half-maximum (FWHM) of 12.2 ns. A long-term test with the maximum repetition rate of 3 kHz is conducted to realize high-voltage output and high-frequency operation simultaneously.

With the development of the ultrahigh voltage (UHV) and extra high voltage (EHV) electric power industry in China, gas insulated substation (GIS) is applied widely. Very fast transient overvoltage (VFTO) caused by disconnector operations in GIS may damage the insulation of equipment due to its high frequency and amplitude. As one of the main overvoltage protection equipments, the protection behavior of surge arresters has received extensive attention. In this paper, the residual voltage behavior, the impedance behavior, and the response behavior of five different representative arrester blocks when excited by VFTO and lightning are investigated, respectively. Experimental results present that when the current peak keeps constant, the residual voltage under VFTO is approximately 14.7%–18.2% higher than under the standard lightning impulse voltage (8/20 μs, LI). The arrester block presents different impedance behavior under VFTO and LI. It behaves dominantly inductively under LI and expresses an impedance converting behavior under VFTO. Furthermore, the diameter and the shape of arrester blocks have little impact on the ratio of $V_{0}$ to $V_{{\rm 1mA}}$ under VFTO. Therefore, the protective effect of arresters varies slightly under VFTO and LI. Investigating behavior of arrester blocks under VFTO in comparison with under LI could be applied not only in VFTO simulation and insulation coordination but also in the design and the operating of metal oxide surge arrester in GIS.

Avalanche transistor (AT)-based repetitive nanosecond pulse generators with high amplitude, fast rise time, narrow pulse width, and low jitter have been widely developed and applied in numerous fields. However, relatively little research has been carried out on the positive nanosecond pulse generation with high flexibility in a wide range of output voltage amplitude. In this article, a novel AT-based Marx circuit (MC) topology adopting base-triggering method is proposed to avoid the formation of current filamentation inside the transistors and resolve the contradiction between high-voltage output and high repetition rate operation. A 6×10-stage MC prototype is implemented with optimized parameters to validate the feasibility of the proposed topology. The conduction processes of transistors show that, with the injection of additional base current, the switched-ON modes are transformed, which contributes to reliable conduction of transistors even without sufficient overvoltage ramp. With the adoption of inner triggering loops, the minimum working voltage of the prototype is extended to 1150 V. The operation characteristics of the generator in the whole operation range are investigated in depth. Experimental results illustrate that, at the 75- Ω match-ended coaxial cable, the prototype is capable of generating positive pulses with an adjustable voltage amplitude in the range of 6.50 to 12.39 kV, a basically consistent rise time of 3.6 ns and pulse width of 19.5 ns. Over 10 ⁷ successive pulses are generated at a maximum repetition rate of 1 kHz without any device failure.

This paper presents theoretical and experimental results on the energy loss characteristics of reversely switched dynistor (RSD) under high-current conditions. Theoretical analysis was performed based on a 1-D modified model by taking account into the carrier-carrier scattering effect and auger recombination effect during the conducting process. The experimental results of energy losses in RSD at various amplitudes of high pulse current were accurately obtained using the direct current injection method. The typical experimental results show that a single RSD has a voltage drop of approximately 9 V with a pulse current of 150 kA, transferred charge of 26.5 C. The theoretical calculated voltage drop based on 1-D modified model is approximately 7.7 V under the same conditions. The theoretical results based on the 1-D modified model almost agree well with the experimental results.

Due to its low-loss and high dielectric strength, polypropylene is widely used as electrical insulation material in pulse capacitors. In order to study its breakdown characteristics for nanosecond voltage pulses, an experimental setup was designed to generate voltage pulses with a 10%-90% rise time of 38 ns and a full width at half maximum of about 90 ns. Tests of the three polypropylene films with thicknesses of 12, 15, and 18 μm were performed. In addition, hundreds of nanoseconds pulse and dc voltage were also applied for comparison. The experimental results reveal that most of the breakdown occurs during the front edge of the pulse for tens of nanoseconds pulse, and the breakdown strengths of the three kinds of polypropylene films are almost identical for different applied voltages, which show a weak correlation between the thickness of the dielectric and the breakdown field. The expected breakdown strength of tens of nanoseconds pulse defined in this paper is not significantly higher than the mean value of the hundreds of nanoseconds pulse and the dc condition, suggesting that the breakdown of a thin polypropylene film is mainly determined by the electrical field but not the voltage-time cumulative effect. All these observations strengthen the conclusion that the breakdown of a thin polypropylene film is an intrinsic phenomenon.