Post Arc Research Articles

Observation of the dynamic evolution process of vacuum arc microscopic particles based on the emission spectrum principle

The distribution of microscopic particles directly affects the recovery of the post arc insulating medium and determines whether the fault current can be interrupted. Based on the principle of vacuum arc emission spectrum, a high-speed spectrum observation platform was built to study the distribution of microscopic particles during the arc burning, and the axial and radial spectral line intensity and density distributions of atoms and ions under different current amplitudes were obtained. The results show that the CuI spectral line intensity has two peaks near the cathode and anode, while in the arc column it is relatively low. The peak of the CuI spectral line intensity near the electrode is caused by electrode evaporation. The peak duration of the CuI spectral line intensity near the cathode is always longer than that near the anode. The CuII spectral line intensity is lower, appears later and disappears earlier, which in the arc column increased obviously, compared with CuI. The CuII density near the cathode is higher than that near the anode, and the CuII density in the arc column is higher than in the two electrodes, which is similar to the axial distribution of electron density. The radial distribution curve of CuI and CuII density is similar to the radial distribution curve of spectral line intensity, and displays the characteristics of a high center and low edge in the radial direction of the arc gap. The difference is that the width of the atomic spectral line is larger than that of the corresponding ionic spectral line, the distribution curve of the ionic spectral line is smooth and symmetrical, and the radial attenuation rate of the CuII density is larger than that of the corresponding CuI. This reflects the ionization of atoms and the effect of magnetic fields. The radial and axial distribution of the particle density is opposite to that of the excitation temperature. Electrode emission will first affect the atom formation.

Step-cut, biplanar, elongation and angulation ulnar osteotomy with annular ligament reconstruction in neglected Monteggia fracture dislocation in children: a retrospective study

Monteggia fracture dislocation is an infrequent injury in children, with around 20-50% cases being missed on initial consultation; leading to their chronic and neglected forms leading to number of complications; thus justifying their operative management. Various treatment modalities have been suggested in the literature for these neglected injuries. A retrospective study of 7 patients (5 males and 2 females), with mean age of 9.58 years (7-14 years); with neglected Monteggia fracture dislocation undergoing corrective reconstructive surgery in the form of elongation and angulation proximal ulnar osteotomy with radial head reduction combined with annular ligament reconstruction was conducted and was then evaluated clinically and functionally using Mayo Elbow Performance Index (MEPI) score; and radiographicaly were graded as good, moderate or poor. The mean interval from time of injury to the time to corrective surgery was 10.58 weeks (range 6-16 weeks). The mean improvement in the post operative MEPI score was 23.57. The mean improvement in the post operative flexion-extension arc was 28.57˚, while that in the supination-pronation arc was 20.72˚. We concluded that Step-cut, biplanar, elongation and angulation proximal ulnar osteotomy with additional reinforcement in the form of annular ligament reconstruction is an effective technique to treat neglected Monteggia fracture dislocations in children; having excellent clinical, functional and radiological outcomes.

Lifetime estimation and surface degradation of MCCB contact tips due to multiple electrical interruptions

This paper presents the surface degradation analysis of contact tips of commercial (20A, 110 V) molded case circuit breaker due to multiple electrical interruptions during experimental electrical test. In the experimental electric test, and according to the post arc current observation, the arc voltage and current were categorized. Multiple high-current interruption has been identified, and the phenomena that regulate the interruption failure have been established. Also, post-arc current sprinted for a short period of time (10–200 µs) during multiple electrical interruptions. These interruptions cause the failure of the contact tips of MCCB. The metallurgical changes were also observed on the contact tips. The braze joints between contacts tips and copper base is also affected by thermal and electrical conductivity during the electrical interruptions. The optical microscope reveals the typical metallurgical changes that occur during a breakdown, such as surface degradation, wear, cracks adjacent to the braze interface, oxide layer formation, cracks on the contact tips, and cracks that penetrate into the copper base. The experimental investigation of the factors influencing the post arc current was carried out to learn more about the link between the post arc current and the degradation of the interruption characteristics. This investigation’s primary objective is to explore the interruption performance and failure analysis of commercial MCCBs.

The conceptual design of upgraded 100 kA quench protection system for CRAFT superconducting magnet

In the previous scheme of 100 kA Quench Protection System (QPS) in Comprehensive Research Facility for Fusion Technology (CRAFT) project, advanced artificial current zero-crossing technology was used to interrupt the current. Also, the feasibility was verified by both simulation and experiment. However, some significant issues were exposed, including the breaking reliability problems caused by randomness of the post arc and uneven distribution of the recovery voltage in vacuum circuit breaker. In view of the problems, it is of great significance to upgrade the QPS design scheme in CRAFT project. In this paper, a new 100 kA/10 kV QPS topology is proposed, and the working principle of the new topology is introduced firstly. Then the complete commutation process is divided into three stages to carry out a more effective analysis of the theoretical feasibility of the new topology. Furthermore, a series of simulations including the electrical performance of each device in commutation process and temperature prediction simulation of the used semiconductors are carried out. Finally, the optimized design scheme is obtained to meet the technical requirement of CRAFT project. Compared with the previous QPS scheme, the new scheme has much higher action speed and lower cost.

Recovery Time Representation Based on Post Arc Plasma Dissipation Using a Vertical Extension Arcing Horn

A suitable reclosing time is important to guarantee the reliability of the power supply after a temporary failure in dc transmission lines. The design of the reclosing time mainly depends on the recovery time of the insulation strength. Here, an experimental platform was built that can simulate a real situation using a vertical extension arcing horn based on the post arc plasma dissipation. The entire macroperformance process, voltage and after-current characteristics were analyzed. The recovery times were measured under the conditions of the output current from 10 to 200 A and an initial gap length from 1 to 80 mm. The results show that the after-current can better represent the recovery time. The recovery time is a double-exponential function of the gap length and a power function of the initial current. The longest recovery time is 210 ms when the current is 200 A and the initial gap length is 1 mm, while the shortest recovery time is only 60 ms when the current is 10 A at an initial gap length of 40 mm. The entire process of the macroperformance contains three periods: the arc fuse burst, the transient arc extinction, and the post arc plasma dissipation. The maximum gap length for generating a continuous dc arc via the arc fuse is 0.4 mm when the terminal voltage is 560 V and the minimum current for this dc arc's maintenance is 3.5 A under the condition of the maximum gap length. This article is aiming to provide some references for the reset of the reclosing times used in dc transmission grounding lines.

Analysis of electron and heavy particle velocity distribution under consideration of nonthermal equilibrium arc

AbstractThe circuit breaker is required to interrupt the current in order to prevent the spreading fault current. The reignition caused by the remaining high‐temperature gas in the opening of circuit breaker occurs. As this countermeasure, the external magnetic field application and blast gas to arc are used in order to decrease the arc temperature. It has been reported that the nonthermal equilibrium of arc is remarkable near the electrode and post arc. However, few reports have the analysis of separating electron and heavy particle momentums under consideration of the nonthermal equilibrium because the physical phenomena are complicated in the nonthermal equilibrium. In this paper, the electron and heavy particle velocity distribution under consideration of nonthermal equilibrium arc were analyzed. As a result, it is possible to quantify the electron and heavy particle velocity. The electron velocity distribution is dominant to the electric potential distribution. On the other hand, the heavy particle velocity distribution is dominant to the pressure gradient. Therefore, the difference between the electron and heavy particle velocity distribution was elucidated.

Post-Arc Characteristics of High-Current Arcs in Vacuum Circuit-Breakers

The post-arc (PA) characteristics of vacuum arcs in transverse magnetic field contacts are studied for short-circuit currents of up to 123 kA peak and transient recovery voltages below 875 V. The measured PA currents are interpreted in terms of an Electric Resistance Model and the models of Andrews-Varey, Langmuir-Child, and Slepian-Schmelzle. Whereas in the late PA period, the calculations do not agree well with the measurements, the PA behavior is well described in the early period after current-zero. It is concluded that the PA discharge is amplified by ionization of metal vapor particles in the boundary sheath due to electron impact.

Experimental Assessment of PTFE Post-Arc Ablation

The study addresses the post arc ablation (PAA) of PTFE (Polytetrafluoroethylene) material after being stressed by high current arcs. Arcs were generated in ambient air applying AC or DC current profiles to reach energy input in the range 7-22 kJ. The characterization has been performed essentially based on standard optical measurement techniques. The shadowgraph technique enabled us to show that the PAA flow is composed by a significant amount of carbonaceous soots lasting for several dozens of milliseconds after current interruption. The pyrometry technique allowed to estimate the soots temperature in the range 1400-2200 K.

Characteristics of high frequency interruption for vacuum DC breakers

Post arc current can reflect the residual plasma in the electrode gap and the zero zone characteristics, so it has a great influence on the interruption of the breakers. In this paper, a permanent magnet-repulsive force hybrid actuator is designed, and the post arc current measurement system is established. Based on the forced current zero method, a series of high frequency DC interruption experiments are carried out in the synthetic test circuit with vacuum interrupters. The influence of the commutation frequency and recovery voltage on the vacuum DC interruption is investigated. The results show that a short lag phase about 80 ns exists between the post arc current and recovery voltage. High commutation frequency leads to the rise of the post arc current, which is disadvantageous for the vacuum DC interruption. The post arc current also rises with the increase in the recovery voltage. The interruption is not just affected by the di/dt and du/dt. In this study, failing interruption at the first current zero happens when the transient recovery voltage is near 2800 V. The current chopping occurs easily at high commutation frequency. And the chopping current value is proportional to the commutation frequency, which is up to 120 A at 4.0 kHz.

Experimental and theoretical study of decay and post-arc phases of a SF6 transfer arc in DC hybrid breaking

During DC hybrid breaking, the transfer arc temperature decays quickly due to fast current commutation from the mechanical switch to the parallel connected branch, which may lead to deviation from thermal equilibrium. In this study, numerical investigation on a two-temperature calculation for SF6 transfer arc has been performed in order to study the arc’s behavior under the effect of thermal non-equilibrium. The free decay and post-arc phase have been studied. This model allows us to calculate electron and heavy-species temperatures, gas velocity, and electron number density. In addition, various energy exchange mechanisms including radiation, ohmic heating, and elastic collision energy are discussed. It has been predicted that the departure from thermal equilibrium appears near the arc edge and electrodes due to insufficient collision energy exchange between electrons and heavy species. Particularly the formation of a circular velocity vortex makes the gas temperature in the vortex zone exceed the arc core temperature at zero current, which does not favor the residual plasma withstanding the recovery voltage at post arc. After carrying out a simulated hybrid breaking experiment, the dynamic motion process of the transfer arc and post-arc current were determined experimentally and compared to theoretical results obtained from a two-temperature model. This comparison validated the model and showed that the presence of a vortex high-temperature zone is more prone to cause the breakdown.

The study on limited asynchronous breaking based on the adjustment of breaking time

Multi-interrupter in series is the only way for high voltage circuit breaker to develop Ultra high voltage levels. It is especially important for multi-interrupter in series to keep synchronization in breaking, but synchronous breaking of multi-interrupter is relative, and asynchronous breaking is absolute, so the conception of limited asynchronous breaking is brought up in this paper. Research on the compensation of dynamic dielectric recovery based on active asynchronous, and make each vacuum circuit breaker (VCB) has a different instantaneous gap length at current zero-crossing, to realize active compensation for dynamic dielectric recovery. In this paper, the model of post arc resistance will be established by ATP DRAW within the research of VCB with triple-interrupters as background, research the limited asynchronous breaking and the dynamic dielectric recovery characteristics of the various interrupter by adjusting the breaking time of the VCB, and the gain analysis of insulation breakdown voltage is analyzed. At last, the module of double-break VCB is established, and the correctness of simulation results is proved by tests.

Influence of the pulsed AMF arc control on the vacuum arc and post arc characteristic in vacuum interrupters

The paper investigates the influence of the pulsed AMF arc control on the vacuum arc and the post arc characteristic to reveal the mechanism of AMF arc control in different control time and find the proper AMF arc control. The pulsed AMF control system is designed and the pulse width is adjusted from 1.5 ms to 10 ms by changing the capacitors. The test circuit is set up in the synthetic test circuit and the test vacuum interrupter (VI) is transparent in order to observe the development of the vacuum arc by the high speed CMOS camera. The rated voltage and current of the test VI is 10 kV and 25 kA respectively. The post arc current of the test VI is measured in order to analyze the post arc characteristic, such as the post arc charge, post arc conductance and dynamic dielectric strength. The development of vacuum arc and the post arc characteristic influenced by the pulse width, magnitude and control time of the pulsed AMF is obtained, which is useful to special magnetic contacts design.

Investigating influence of the magnetic arc blow in multi-break vacuum circuit breakers

This paper investigates the influence of the interactive magnetic field in multi-break vacuum circuit breakers (VCBs) on the arc plasma and the post-arc characteristics. The magnetic field of multi-break VCBs is asymmetric and off-center because of the interactive magnetic field, which is also called bias magnetic field (BMF). The BMF distribution of double-break VCBs is gained by electromagnetic analysis. The test circuit of the magnetic arc blow in multi-break VCBs is established by simplifying as the interaction between the vacuum arc and the BMF. The influence of the magnetic arc blow on the arc plasma is studied by the high-speed CMOS camera and the post-arc current measure. While the vacuum arc is in the direction of the Ampere force with the BMF at 200 mT, it is in the retrograde direction when the BMF is below 100 mT, which results in the post-arc charge obviously varying from 9 μC to 50 μC. The relationship between the BMF and the post arc charge is gained. The mechanism of the magnetic arc blow in multi-break VCBs is discussed. Therefore, this paper can provide the base of construct and configuration to avoid the influence of the magnetic arc blow.

Investigation on the current-zero characteristic of vacuum circuit breakers

The current-zero characteristic of vacuum circuit breakers (VCBs) has an important influence on the dynamic dielectric recovery and the success of the breaking test. In the paper, the characteristic of the post-arc current, post-arc charge and the post-arc conductance at current-zero is researched to obtain the influence of the arc memory on the current-zero characteristic and the post-arc characteristic. Based on the synthetic test circuit, the test plat of the current-zero characteristic is set up and the test VCB is a transparency vacuum interrupter in order to observe the development and extinguishing process of the vacuum arc by the high speed CMOS camera. The distribution law of post-arc characteristic is gained by measuring and processing the post-arc current. The relationship between the post arc charge and the final position of last cathode spot is investigated. The current-zero characteristic of VCBs supply the base for controlling vacuum arc, improving the breaking capacity, which maybe also useful to VCBs with multi-break.

Research of Arc Chamber Optimization Techniques Based on Flow Field and Arc Joint Simulation

The preliminary design of an arc chamber in the 550 kV SF6 circuit breaker was proposed in accordance with the technical requirements and design experience. The structural optimization was carried out according to the no-load flow field simulation results and verified by no-load pressure measurement. Based on load simulation results such as temperature field variation at the arc area and the tendency of post arc current under different recovery voltage, the second optimal design was completed and its correctness was certificated by a breaking test. Results demonstrate that the interrupting capacity of an arc chamber can be evaluated by the comparison of the gas medium recovery speed and post arc current growth rate.

Dielectric recovery process in vacuum interrupters regarding to contact materials during post arc interval

This investigation presents new practical achievements concerning the velocity of dielectric recovery process inside a vacuum interrupter chamber. According to Andrews- Varey equations, a new model is developed using Matlab-Simulink software. This model is used for doing a new research on inter electrode plasma diffusion, which is the most important factor during insulation recovery interval. The developed model is performed so that it can predict the ionic sheath expansion velocity and post-arc current waveform caused by transient recovery voltage (TRV). One of the faced challenges is to obtain plasma parameters to be utilized based on the previous experimental results. Considering the initial conditions and the related software model Applied to nine different contact materials, and similar 100A quenching current, the achieved results are investigated in details. The main goal is to specify the influence of material (ion mass) and other parameters on the speed of inter-electrode plasma dispersion and voltage recovery process which will guide the designer towards selecting suitable contact material with regard to TRV waveform. Furthermore the effect of TRV value which is applied to the chamber is also investigated in details. In future works this model may be developed so that it can be applied to new metallic alloys made of doped various chemical elements.

Study on Static and Dynamic Voltage Distribution Characteristics and Voltage Sharing Design of a 126-kV Modular Triple-Break Vacuum Circuit Breaker

The static and dynamic voltage distribution characteristics and voltage sharing design of a 126-kV modular triple-break vacuum circuit breaker (VCB) was discussed in this paper. The finite-element method and power frequency tests were used to calculate and verify the static voltage distribution ratios and distributed capacitance parameters of multi-break VCBs, respectively. A model combining the post arc current model and equivalent capacitance model was proposed for simulations of dynamic transient recovery voltage (TRV) distribution characteristics of the triple-break VCB. The simulation results indicated that besides the stray capacitances, the TRV sharing design should take the influence of residual charge (RC) into account, and the influence of RC on the TRV distribution is relevant to the differences of RC parameters among the series interrupters. Therefore, the appropriate value of grading capacitors should meet the requirement of the worst case. Based on the investigation of this paper, a 126 kV U-shaped triple-break VCB prototype with 1000 pF grading capacitors has been produced, and the successful large current breaking tests indicate the good breaking capacity and suitable voltage sharing design of the triple-break VCB.

Removal of Methylene Blue from Aging Water Solutions Treated by a Submerged Arc

Low voltage, low energy submerged pulsed arcs with a pulse repetition rate of 100 Hz, energies of 2.6–192 mJ and durations of 10–40 μs, followed by aging in the dark, were used to decompose 10 mg/l methylene blue (MB) dissolved in 40 ml of water, with the addition of 0.5 % H2O2. Electrode pairs composed of Fe/Fe, Ti/Ti, Cu/Cu, Cu/Fe, Fe/Cu, Ti/Fe, Fe/Ti, Cu/Ti and Ti/Cu were used. MB degraded during arc treatment, and during post arc treatment aging. The aging degraded MB faster (by a factor of ~2–3) when the MB solution was subjected to arcing with dissimilar electrodes when one of them was Cu, than for arcing with other used electrode pairs. The impact of the arc treatment time and the electrode materials on the MB removal ratio (C0–Cta)/C0 was determined as a function of aging time ta, where C0 and Cta are the MB concentrations initially and after ta. For a pulse duration of 10 μs and pulse energies of 2–20 mJ, the MB removal rate increased linearly with treatment time and its growth rate increased with pulse energy. The linear dependence of the MB removal rate on treatment time was violated with pulse duration of 40 μs and pulse energies of 30–200 mJ. Kinetics of the MB degradation during aging of the arc treated solution was well described by the 1st order linear rate equation.

Influencing Factors of Breaking Capacity of Double-Break Vacuum Circuit Breakers

Using a series arrangement of two vacuum interrupters (VIs) has been proved to be an effective way of developing higher voltage vacuum circuit breakers (VCBs), which are known as double-break VCBs. The uniform distribution of the transient recovery voltage (TRV) across each VI is very critical for the breaking capacity of double-break VCBs. In this paper, the TRV distribution characteristics of double-break VCBs was studied by the synthetic test and the PSCAD/EMTDC simulation based on a vacuum arc interruption model. The results show that the bias of the TRV distribution ratio is caused by the stray capacitance and the imbalanced post arc plasma characteristic in each VI, which is consistent with the theoretical analysis. Moreover, the negative effect of grading capacitors was discussed. The results show that it is advisable to limit the value of grading capacitors to those ranges which can guarantee sufficiently improve the voltage distribution. DOI: http://dx.doi.org/10.11591/telkomnika.v11i6.2140

Relationship Between the Voltage Distribution Ratio and the Post Arc Current in Double-Break Vacuum Circuit Breakers

In many cases, single-break vacuum circuit breakers are used as circuit breakers, and so the characteristics of double-break vacuum circuit breakers have not received sufficient attention. This report describes our investigations of the interruption characteristics of double-break vacuum circuit breakers. We have investigated and clarified the relationship between the voltage distribution ratio and the post arc current in double-break vacuum circuit breakers by measuring the post arc current in the single-break vacuum circuit breaker, the voltage distribution ratio, and the post arc current in double-break vacuum circuit breakers. Our investigation has shown that the post arc current scatter of the spiral contact is much larger than that of the axial magnetic field contact. This result shows that the bias of the voltage distribution ratio was caused by the imbalanced post arc current in each vacuum interrupter in the double-break vacuum circuit breaker. Therefore, we conclude that axial magnetic field contacts are suitable for double-break vacuum circuit breakers.