Voltage Rise Rate Research Articles

Upgrading of the Vyborg Converter Substation: Analysis of Lightning Impulse Voltage Withstand Capability

The basic design of the high-voltage thyristor valve developed for the Vyborg converter substation is described. The parameters of the design impulse voltage across the valve and the model of the converter bridge valve assembly are justified. It is established that when subject to a design lightning impulse voltage, the designed valve ensures safe operation in terms of the voltage amplitude and voltage rise rate in the thyristors. It is shown that the difference between the detailed and simplified model does not exceed 3%.

Evaluation of voltage endurance characteristics for new and aged XLPE cable insulation by electrical treeing test

The voltage endurance coefficient of solid insulating materials can be determined by electrical treeing tests. The measured value is influenced by the test conditions, and its effectiveness remains to be further demonstrated. In this study, samples were made from the XLPE insulation of three 110 kV AC cables, two new and one operated for 16 years. In treeing tests performed with a pin-plane electrode system, the tree initiation times were measured under both progressive and constant voltage, and voltage endurance coefficients were determined by the residual voltage method. The material properties of XLPE were measured using the FTIR, DSC and TSC methods. For the same sample, the voltage endurance coefficient measured with a 10 μm needle electrode was larger than that measured with a 5 μm electrode, indicating the influence of space charges on the electrical field around the needle tip. For the insulation samples of the two new cables, the measured voltage endurance coefficients were different, and the difference became more significant when the rise rate of the progressive voltage decreased. The superior resistance to electrical aging of the insulation with a higher voltage endurance coefficient was confirmed via material property measurements. For the insulation samples of the aged cable, along with a decrease of the progressive voltage rise rate, the tree initiation voltage increased, which was opposite to the test results obtained for the new cable insulation samples. The voltage endurance coefficient could not be measured using the residual voltage method because the trees always initiated at the rising edge of the constant voltage, except for a low value measured at the lowest constant voltage. The abnormal performance of the aged cable insulation might be the result of increased defects and impurities caused by operation aging, which enhanced the space charge effect, especially in the pin-plane electrical field of the electrical treeing test.

Зависимость потенциала пробоя от скорости роста напряжения в длинной разрядной трубке при низком давлении

The dynamical breakdown voltage in a long (80 cm) discharge tube is measured for neon, argon, their mixture, and argon with mercury vapors at a pressure of 80 – 400 Pa in a wide range of anode voltage rise rate (dU/dt ~ 10–4 – 102 kV/ms). Non-monotonous dependence of the breakdown potential on the dU/dt magnitude is found, with the minimum at 0.1 – 10 kV/ms values. The growth of the breakdown voltage at higher dU/dt is caused by existence of the breakdown delay time. The increase in the breakdown potential in a lower voltage rise rate is presumably due to specialty of the breakdown in long tubes and is a result of the deposit of the surface charge on the tube wall. The charge diminishes potential difference between the anode and the wall, so obstructing the initial breakdown between them. The data of additional experiments with the pulses raised to the constant level pedestal confirm the possibility of such explanation.

The method of processing the droplet-air flow by non-equilibrium plasma

The paper considers a fundamentally new installation for the processing of a droplet-air environment in a non-equilibrium plasma. Its various designs are presented. This installation is built on the basis of pulsed energy devices and is intended for water disinfection and decomposition of dissolved organic compounds, the production of nanomaterials, research in physics and chemistry, etc. We have conducted research of the performance and energy efficiency of this method of processing. It is established that in obtaining the target product, this method of processing has an advantage over the known methods: due to high performance and energy efficiency, as well as the simplicity of this processing method. In addition, the parasitic load capacity of the nanosecond generator is reduced several times, this fact increases the voltage rise rate on the cells of the plasma plasmatrons, which improves performance and energy efficiency.

Features of Switching Memristor Structures to a High-Resistance State by Sawtooth Pulses

It has been experimentally established that the time of switching by triangular pulses in Ti—TiN–ZrO2(Y)–Zr–Au memristor structures from the state of low resistance to the state of high resistance is inversely proportional to the voltage rise rate, i.e., the bias current through the memristor structure. A mechanism for the influence of a bias current on the switching time of the structure has been proposed.

A phase-stabilized superradiant Ka-band oscillator driven by nanosecond voltage pulses with amplitude variations and reduced rise rates

This paper presents the results of experiments and a numerical simulation of the conditions for phase stabilization (standard deviation < 0.5 rad) of a subgigawatt relativistic superradiant Ka-band backward wave oscillator with the accelerating voltage amplitude varying within 15%. It is shown that phase stabilization can be achieved for the voltage rise rate (dU/dt)max ∼ 2 MV/ns by using our recently developed approach. Particular emphasis is given to the cases of substantially lower voltage rise rates at which stabilization of the microwave oscillation phase is also possible. The mode with (dU/dt)max ≪ 1 MV/ns is considered for specific voltage waveforms that ensure efficient kinematic peaking of the beam current. In this case, stabilization of the microwave oscillation phase can be achieved by initiating a voltage prepulse, provided that the accelerating pulse leading edge has a segment of stable rise rate and stable shape.

Semiconductor opening switch generator with a primary thyristor switch triggered in impact-ionization wave mode.

The results of the investigation involving a thyristor switch triggered in the impact ionization wave mode are presented. This switch is intended for operation as a primary switch in a nanosecond pulse generator with a semiconductor opening switch (SOS). The thyristor switch is based on commercial low-frequency tablet thyristors stacked in a joint assembly of up to 6 pieces connected in series. At a charging voltage of 2-12 kV and switching energy of up to 16 J, the switch operates with a discharge current of up to 8 kA, a current rise rate in the range from 14 to 54 kA/μs, and a switching efficiency of ∼0.9. It is shown that an increase in a voltage rise rate on thyristors at the triggering stage reduces energy loss in the thyristor switch during the current flow. The SOS pumping circuit contains one magnetic element-a pulse transformer, which simplifies the generator and increases its efficiency. The SOS generator has an output voltage of up to 300 kV and a peak power of up to 250 MW with a pulse duration of ∼50 ns. The thyristor switch in the generator operates at a voltage of 12 kV and provides current flow with the amplitude of up to 7.5 kA with a duration of ∼500 ns and a current rise rate of ∼54 kA/μs. The pulse repetition frequency of the generator is 1 kHz in the burst mode of operation.

Joint effect of temperature and voltage rise rate on the switching process of Si thyristors triggered in impact ionization wave mode

The joint effect of temperature and voltage rise rate in the structure of Si thyristors on the process of their switching to the conductive state by impact ionization wave has been studied by experimental and numerical simulation methods. In the experiments, the rate of voltage rise dV/dt across the structure varies from 0.5 to 10 kV ns−1, and the temperature varies from 25 °C to 180 °C. It is shown that the main factor determining the nature and parameters of the thyristor switching process is the value of dV/dt. For dV/dt ≥ 4 kV ns−1, the impact ionization wave is triggered upon switching of the thyristor at the temperature of the structure up to 180 °C. However, at dV/dt ≤ 1 kV ns−1, the wave switching effect disappears when the temperature becomes over ∼110 °C–120 °C. Numerical simulation demonstrates that an increase in the value of dV/dt will increase the electric field in the structure and compensate for the decrease in the intensity of impact ionization processes with increasing temperature.

Effects of Pulsed Power Control on Plasma Water Treatment Using LTD

We have studied a water treatment by pulsed discharge plasma. To produce the plasma, pulsed high voltage is applied to an electrode. At previous studies, effects of peak, width, rise rate, and repetition rate of pulsed voltage have been confirmed. According to the studies, there is more loss at a latter part of a pulse. To reduce the loss, we investigated an effect of lowering the latter part of the pulse. In addition, an effect of periods between pulses was also investigated for optimization of pulse application timing. Those are new investigations, which were able to be carried out by various pulse forming technologies using a solid-state linear transformer driver. As the result, energy efficiency for organic compounds decomposition increased with a decrease of the latter part of pulses and with an increase of periods between pulses. A possible reason of that is the decrease of disappearance reactions of radicals owing to the decrease of those concentrations. Hence, short pulse and long periods realizes water purification of high-energy efficiency.

Investigation of the prebreakdown stage of the self-sustained subnanosecond discharge in high pressure nitrogen

The results of the investigations of the prebreakdown stage of the self-sustained subnanosecond discharge in nitrogen at pressures between 5 and 40 atm are presented. A high voltage pulse with a front of approximately 250 ps at the level of 0.1–0.9 in amplitude (full duration of the pulse front was 500 ps) was applied to the studied gas gap. In this case, the voltage rise rate in the discharge gap at the prebreakdown stage reached up to 7 × 1014 V/s. Breakdown occurs at the front of the voltage pulse. During these experiments, the parameters of the voltage pulse at the output of the pulse generator were not modified. In this study, it was discovered that increasing of the pressure from 5 atm to 40 atm leads to a significant decrease in the overvoltage in the discharge gap. It is shown that at pressures above 10 atm, the delay time of breakdown is less than the time of growth for electron avalanches to reach a critical size. The critical length of avalanche is approximately one order of magnitude less than the length of the discharge gap. Hence, the avalanche-streamer model is inapplicable in this situation. A mechanism of subnanosecond breakdown initiation with a help of runaway electrons at pressures above 10 atm has been suggested.

Solid-state repetitive generators of short GW-range pulses: a review

The paper presents a brief review of solid-state repetitive generators of nano- and subnanosecond pulses with GW-range of peak power developed by Institute of Electrophysics. The base of the described approach for obtaining such pulses consists in using solid-state generators with its output unit containing intermediate inductive storage and semiconductor opening switch (SOS). The most powerful SOS generator of S-500 type is described. The generator provides a peak power of up to 6 GW, an output voltage of 500–900 kV, a voltage rise time of 2–3 ns, a pulse length (full width at half maximum, FWHM) of 5–7 ns across external loads of 40–100 Ω, and a pulse repetition frequency up to 1 kHz in the burst mode of operation. To reduce the voltage rise time of S-500 generator semiconductor sharpeners are used. The sharpeners are made as stacks of series-connected dynistor structures built into an oil-filled coaxial line at the place of an inner conductor. An input voltage pulse has the amplitude of 540 kV with the rise time of ∼1.2 ns and voltage rise rate of ∼0.3 MV/ns. After pulse propagation through the sharpening sections, its rise time is reduced down to 360 ps, and the voltage rise rate is increased up to ∼0.95 MV/ns. Peak power of the sharpened pulse is within the range of 4.5–5.5 GW. It is shown, that gyromagnetic nonlinear transmission line (NLTL) can operate as a magnetic pulse compressor. At such an operating regime, the duration of the input pulse is close to the period of generated oscillations, and the main part of the input pulse energy is transmitted only to the first peak of the oscillations. In energy compression experiments, the input pulse with amplitude of 500 kV and FWHM of 7 ns is applied to the NLTL. At the output of the NLTL in 40 Ω coaxial transmission line, the pulse amplitude is increased to 740 kV and the pulse duration is reduced to ∼2 ns, which correspond to power amplification of the input pulse from ∼6 to ∼13 GW. In pulse sharpening experiments, a three-stage NLTL is used. The system provides a peak power of 15 GW in 44-Ω line, FWHM of 120 ps, and a record high level of the voltage rise rate of 10 MV/ns. Applications of the developed generators are given.

Void discharge behaviours as a function of cavity size and voltage waveform under very low‐frequency excitation

Measurement of partial discharge (PD) is a vital method to assess the health of the electrical insulation in high-voltage power equipment. As diagnostic testing at very low frequency (VLF) is increasingly being used, it is important to investigate PD behaviours under such a low-frequency voltage excitation. This study presents the PD characteristics at VLF excitation under different applied voltage waveforms, including sinusoidal and trapezoid-based waves. Also, the effects of cavity size on PD behaviours at VLF are investigated. Experiments were performed to measure PDs in a cylindrical void bounded by solid insulation. The results show that discharge activities at VLF, in general, exhibit lower magnitude and repetition rate when compared with power frequency. Also revealed is the strong dependency of discharge parameters on the rate of voltage rise. Physical mechanisms to explain discharge behaviours are given.

Facile Fabrication of Ordered Anodized Aluminum Oxide Membranes with Controlled Pore Size by Improved Hard Anodization.

We have fabricated highly ordered anodized aluminum oxide (AAO) membranes with different diameter through improved hard anodization (HA) at high temperature. This process can generate thick AAO membranes (30 μm) in a short anodizing time with high growth rate 20-60 μm h-1 which is much faster than that in traditional mild two-step anodization. We enlarged the AAO pore diameter by adjusting the voltage rise rate at the same time, which has a great influence on current density and temperature. The AAO pore diameter varies from 60-110 nm to 160-190 nm. The pore diameter (Dp) of the AAO prepared by this improved process is much larger than that prepared by HA (40-60 nm) when H2C2O4 as electrolyte. It can expand potential use of the AAO membranes such as for the template-based synthesis of nanowires or nanotubes with modulated diameters and also for practical separation technology. We also has used the AAO with different diameters prepared by this improved HA to fabricate Co nanowires and γ-Fe2O3 superparamagnetic nanorods.

Characteristics of a Pulse-Periodic Corona Discharge in Atmospheric Air

Pulse-periodic corona discharge in atmospheric air excited by applying a voltage pulse with a subnanosecond or microsecond rise time to a point electrode is studied experimentally. It is shown that, at a voltage rise rate of dU/dt ~1014 V/s, positive and negative ball-shaped streamers with a front velocity of ≥2 mm/ns form near the point electrode. As dU/dt is reduced to 1010−1011 V/s, the streamer shape changes and becomes close to cylindrical. The propagation velocity of cylindrical streamers is found to be ~0.1 mm/ns at dU/dt ~ 2 × 1010 V/s. It is shown that the propagation direction of a cylindrical streamer can be changed by tilting the point electrode, on the axis of which the electric field strength reaches its maximum value. It is established that, for the negative polarity of the point electrode and a microsecond rise time of the voltage pulse, a higher voltage is required to form a cylindrical streamer than for the positive polarity of the point electrode.

Formation of 1.4 MeV runaway electron flows in air using a solid-state generator with 10 MV/ns voltage rise rate

Fulfillment of the condition that the voltage rise time across an air gap is comparable with the time of electron acceleration from a cathode to an anode allows a flow of runaway electrons (REs) to be formed with relativistic energies approaching that determined by the amplitude of the voltage pulse. In the experiment described here, an RE energy of 1.4 MeV was observed by applying a negative travelling voltage pulse of 860-kV with a maximum rise rate of 10 MV/ns and a rise time of 100-ps. The voltage pulse amplitude was doubled at the cathode of the 2-cm-long air gap due to the delay of conventional pulsed breakdown. The above-mentioned record-breaking voltage pulse of ∼120 ps duration with a peak power of 15 GW was produced by an all-solid-state pulsed power source utilising pulse compression/sharpening in a multistage gyromagnetic nonlinear transmission line.

Research on the detecting effectiveness of on-site lightning impulse test for GIS equipment with insulation defects

On-site lightning impulse (LI) test waveform, restricted by the large load capacitance and impulse generator's inherent inductance, has a long wavefront time Tf compared with standard LI, called non-standard LI. The non-standard LI test has been carried out in the field. But its insulation defect detecting effectiveness is not clear. In this paper, a generating system of impulses with different waveform parameters, including double-exponential impulses with different wavefront times in the range of 0.08 ∼ 23.5 μs and an oscillating LI with wavefront time around 10 μs, was established. The insulation characteristics of SF6 gas gap with highly inhomogeneous electric field under impulses with different waveform parameters were investigated. Experimental results show that the insulation defects detecting effectiveness of oscillating LI with long Tf around 10 μs is lower than that of standard LI. Tf plays an important role in the insulation defects detection. With Tf increases, the 50% breakdown voltages for rod-plane gaps have an increased trend. The V-t curve presents a U-shape. Prospective voltage is introduced to evaluate the insulation defects detecting effectiveness. The prospective voltage-time characteristics confirm the conclusion that with the increase of impulse voltage Tf, the detection effectiveness for GIS insulation is reduced. The gap distance has influence on the shape of V-t curve. With distance increase, the 50% breakdown voltage of the gap is more sensitive to the wavefront time Tf and voltage rise rate dU/dt. Corona stabilization effect is not just in relationship with the rise rate of impulse, but also with electrode structure and gas pressure. The critical dU/dt for corona stabilization is calculated for different rod-plane gaps.

Radial Distribution of the Nanosecond Dielectric Barrier Discharge Current in Atmospheric-Pressure Air

Experimental results on the radial distribution of the nanosecond dielectric barrier discharge (DBD) current in flat millimeter air gaps under atmospheric pressure and natural humidity of 40–60% at a voltage rise rate at the electrodes of 250 V/ns are presented. The time delay of the appearance of discharge currents was observed to increase from the center to the periphery of the air gap at discharge gap heights above 3 mm, which correlated with the appearance of constricted channels against the background of the volume DBD plasma. Based on the criterion of the avalanche-streamer transition, it is found out that the development of a nanosecond DBD in air gaps of 1–3 mm occurs by the streamer mechanism.

Особенности переключения мемристорных структур в высокоомное состояние пилообразными импульсами

AbstractIt has been experimentally established that the time of switching by triangular pulses in Ti—TiN–ZrO_2(Y)–Zr–Au memristor structures from the state of low resistance to the state of high resistance is inversely proportional to the voltage rise rate, i.e., the bias current through the memristor structure. A mechanism for the influence of a bias current on the switching time of the structure has been proposed.

Study on the streamer inception characteristics under positive lightning impulse voltage

The streamer is the main process in an air gap discharge, and the inception characteristics of streamers have been widely applied in engineering. Streamer inception characteristics under DC voltage have been studied by many researchers, but the inception characteristics under impulse voltage, and particularly under lightning impulse voltage with a high voltage rise rate have rarely been studied. A measurement system based on integrated optoelectronic technology has been proposed in this paper, and the streamer inception characteristics in a 1-m-long rod-plane air gap that was energized by a positive lightning impulse voltage have been researched. We have also measured the streamer inception electric field using electrodes with different radii of curvature and different voltage rise rates. As a result, a modified empirical criterion for the streamer inception electric field that considers the voltage rise rate has been proposed, and the wide applicability of this criterion has been proved. Based on the streamer inception time-lag obtained, we determined that the field distribution obeys a Rayleigh distribution, which explains the change law of the streamer inception time-lag. The characteristic parameter of the Rayleigh distribution lies in the range from 0.6 to 2.5 when the radius of curvature of the electrode head is in the range from 0.5 cm to 2.5 cm and the voltage rise rate ranges from 80 kV/μs to 240kV/μs under positive lightning impulse voltage.

Semiconductor sharpeners providing a subnanosecond voltage rise time of GW-range pulses.

The article describes semiconductor sharpeners providing a subnanosecond voltage rise time of GW-range pulses. The sharpeners are made as stacks of series-connected dynistor structures built into an oil-filled coaxial line with 48 Ω wave impedance at the place of an inner conductor. Two sequential sections of pulse sharpening are used. An input voltage pulse has the amplitude of 540 kV with the rise time of ∼1.2 ns at 0.2-0.9 level from the amplitude and voltage rise rate of ∼0.3 MV/ns. After pulse propagation through the sharpening sections, its rise time is reduced down to 360 ps, and the voltage rise rate is increased up to ∼0.95 MV/ns. Peak power of the sharpened pulse is within the range of 4.5-5.5 GW. The sharpeners are tested at a pulse repetition frequency of up to 1 kHz. Sharpener operation is studied by numerical simulation methods. Experimental waveforms of output pulses and the corresponding calculated voltage-time dependences are in statistical agreement.