Research

13 pages, 3860 KiB

Open AccessArticle

Properties of Vacuum Arcs Generated by Switching RMF Contacts at Different Ignition Positions

by Sergey Gortschakow, Steffen Franke, Ralf Methling, Diego Gonzalez, Andreas Lawall, Erik D. Taylor and Frank Graskowski

Energies 2020, 13(21), 5596; https://doi.org/10.3390/en13215596 - 26 Oct 2020

Cited by 5 | Viewed by 1670

Abstract

The influence of initiation behavior of the drawn arc on the arc motion, on arc characteristics during the active phase, as well as on the post-arc parameters, was studied. The study was focused on arc dynamics, determination of the anode surface temperature after [...] Read more.

The influence of initiation behavior of the drawn arc on the arc motion, on arc characteristics during the active phase, as well as on the post-arc parameters, was studied. The study was focused on arc dynamics, determination of the anode surface temperature after current interruption, and diagnostics of metal vapor density after current zero crossing. Different optical diagnostics, namely high-speed camera video enhanced by narrow-band optical filters, near infrared spectroscopy, and optical absorption spectroscopy was applied. The initiation behavior of the drawn arc had a clear influence on arc parameters. Higher local electrode temperature occurs in case of the electrodes with ignition point near the outer electrode boundary. This further causes an enhanced density of chromium vapor, even in cases with lower arc duration. The results of this study are important for design development of switching RMF contacts for future green energy applications. Full article

(This article belongs to the Special Issue Environmental Compatible Circuit Breaker Technologies)

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23 pages, 12267 KiB

Open AccessArticle

Effects of Fast Elongation on Switching Arcs Characteristics in Fast Air Switches

by Ali Kadivar and Kaveh Niayesh

Energies 2020, 13(18), 4846; https://doi.org/10.3390/en13184846 - 16 Sep 2020

Cited by 6 | Viewed by 2680

Abstract

This paper is devoted to investigating the effects of high-speed elongation of arcs inside ultra-fast switches (u_contact

\approx

5–80 m/s), through a 2-D time-dependent model, in Cartesian coordinates. Two air arcs in series, one between a stationary anode and a moving [...] Read more.

This paper is devoted to investigating the effects of high-speed elongation of arcs inside ultra-fast switches (u_contact

\approx

5–80 m/s), through a 2-D time-dependent model, in Cartesian coordinates. Two air arcs in series, one between a stationary anode and a moving cathode and the other between a stationary cathode and a moving anode in the arc chamber, are considered. A variable speed experimental setup through a Thomson drive actuator is designed to support this study. A computational fluid dynamics (CFD) equations system is solved for fluid velocity, pressure, temperature, and electric potential, as well as the magnetic vector potential. Electron emission mechanisms on the contact surface and induced current density due to magnetic field changes are also considered to describe the arc root formation, arc bending, lengthening, and calculating the arc current density, as well as the contact temperatures, in a better way. Data processing techniques are utilized to derive instantaneous core shape and profiles of the arc to investigate thermo-electrical characteristics during the elongation progress. The results are compared with another experimentally verified magnetohydrodynamics model of a fixed-length, free-burning arc in the air. The simulation and experimental results confirm each other. Full article

(This article belongs to the Special Issue Environmental Compatible Circuit Breaker Technologies)

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15 pages, 3754 KiB

Open AccessArticle

Research on Vacuum Arc Commutation Characteristics of a Natural-Commutate Hybrid DC Circuit Breaker

by Dequan Wang, Minfu Liao, Rufan Wang, Tenghui Li, Jun Qiu, Jinjin Li, Xiongying Duan and Jiyan Zou

Energies 2020, 13(18), 4823; https://doi.org/10.3390/en13184823 - 15 Sep 2020

Cited by 10 | Viewed by 1970

Abstract

Vacuum arc commutation is an important process in natural-commutate hybrid direct current (DC) circuit breaker (NHCB) interruption, as the duration of vacuum arc commutation will directly affect the arcing time and interrupting time of NHCB. In this paper, the vacuum arc commutation model [...] Read more.

Vacuum arc commutation is an important process in natural-commutate hybrid direct current (DC) circuit breaker (NHCB) interruption, as the duration of vacuum arc commutation will directly affect the arcing time and interrupting time of NHCB. In this paper, the vacuum arc commutation model of NHCB was established by simplifying solid-state switch (SS) and vacuum arc voltage. Through theoretical analysis and experiments, the vacuum arc commutation characteristics of NHCB were studied. The mathematical formula of the effect of main parameters on the duration of vacuum arc commutation is obtained, and the changing law of the influence of the main parameters on the duration of the vacuum arc commutation is explored. The concept of vacuum arc commutation coefficient is proposed, and it is a key parameter that influences the vacuum arc commutation characteristics. The research on the characteristics of vacuum arc commutation can provide theoretical foundation for the structure and parameter optimization of NHCB and other equipment that uses vacuum arc commutation. Full article

(This article belongs to the Special Issue Environmental Compatible Circuit Breaker Technologies)

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17 pages, 3805 KiB

Open AccessArticle

Ablation-Dominated Arcs in CO₂ Atmosphere—Part II: Molecule Emission and Absorption

by Ralf Methling, Nicolas Götte and Dirk Uhrlandt

Energies 2020, 13(18), 4720; https://doi.org/10.3390/en13184720 - 10 Sep 2020

Cited by 2 | Viewed by 1870

Abstract

Molecule radiation can be used as a tool to study colder regions in switching arc plasmas like arc fringes in contact to walls and ranges around current zero (CZ). This is demonstrated in the present study for the first time for the case [...] Read more.

Molecule radiation can be used as a tool to study colder regions in switching arc plasmas like arc fringes in contact to walls and ranges around current zero (CZ). This is demonstrated in the present study for the first time for the case of ablation-dominated high-current arcs as key elements of self-blast circuit breakers. The arc in a model circuit breaker (MCB) in CO

_{2}

with and an arc in a long nozzle under ambient conditions with peak currents between 5 and 10 kA were studied by emission and absorption spectroscopy in the visible spectral range. The nozzle material was polytetrafluoroethylene (PTFE) in both cases. Imaging spectroscopy was carried out either with high-speed cameras or with intensified CCD cameras. A pulsed high-intensity Xe lamp was applied as a background radiator for the broad-band absorption spectroscopy. Emission of Swan bands from carbon dimers was observed at the edge of nozzles only or across the whole nozzle radius with highest intensity in the arc center, depending on current and nozzle geometry. Furthermore, absorption of C

_{2}

Swan bands and CuF bands were found with the arc plasma serving as background radiator. After CZ, only CuF was detected in absorption experiments. Full article

(This article belongs to the Special Issue Environmental Compatible Circuit Breaker Technologies)

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20 pages, 3924 KiB

Open AccessArticle

Ablation-Dominated Arcs in CO₂ Atmosphere—Part I: Temperature Determination near Current Zero

by Ralf Methling, Alireza Khakpour, Nicolas Götte and Dirk Uhrlandt

Energies 2020, 13(18), 4714; https://doi.org/10.3390/en13184714 - 10 Sep 2020

Cited by 1 | Viewed by 1703

Abstract

Wall-stabilized arcs dominated by nozzle–ablation are key elements of self-blast circuit breakers. In the present study, high-current arcs were investigated using a model circuit breaker (MCB) in CO

_{2}

as a gas alternative to SF6 (gas sulfur hexafluoride) and in addition a long [...] Read more.

Wall-stabilized arcs dominated by nozzle–ablation are key elements of self-blast circuit breakers. In the present study, high-current arcs were investigated using a model circuit breaker (MCB) in CO

_{2}

as a gas alternative to SF6 (gas sulfur hexafluoride) and in addition a long polytetrafluoroethylene nozzle under ambient conditions for stronger ablation. The assets of different methods for optical investigation were demonstrated, e.g., high-speed imaging with channel filters and optical emission spectroscopy. Particularly the phase near current zero (CZ) crossing was studied in two steps. In the first step using high-speed cameras, radial temperature profiles have been determined until 0.4 ms before CZ in the nozzle. Broad temperature profiles with a maximum of 9400 K have been obtained from analysis of fluorine lines. In the second step, the spectroscopic sensitivity was increased using an intensified CCD camera, allowing single-shot measurements until few microseconds before CZ in the MCB. Ionic carbon and atomic oxygen emission were analyzed using absolute intensities and normal maximum. The arc was constricted and the maximum temperature decreased from >18,000 K at 0.3 ms to about 11,000 K at 0.010 ms before CZ. The arc plasma needs about 0.5–1.0 ms after both the ignition phase and the current zero crossing to be completely dominated by the ablated wall material. Full article

(This article belongs to the Special Issue Environmental Compatible Circuit Breaker Technologies)

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14 pages, 5138 KiB

Open AccessArticle

DC Current Interruption Based on Vacuum Arc Impacted by Ultra-Fast Transverse Magnetic Field

by Ehsan Hashemi and Kaveh Niayesh

Energies 2020, 13(18), 4644; https://doi.org/10.3390/en13184644 - 07 Sep 2020

Cited by 8 | Viewed by 2156

Abstract

In this paper, the effect of an external ultrafast transverse magnetic field (UFTMF) on a vacuum arc in the diffused mode has been studied. According to the results of studies, a novel approach for making a zero-crossing in a DC arc current has [...] Read more.

In this paper, the effect of an external ultrafast transverse magnetic field (UFTMF) on a vacuum arc in the diffused mode has been studied. According to the results of studies, a novel approach for making a zero-crossing in a DC arc current has been presented. Plasma voltage fluctuations of the vacuum arc, which are caused by UFTMF, have been investigated via finite element simulation and two-fluid description of plasma physics. By making an appropriate UFTMF through an external circuit, the arc current can be commuted successfully from the vacuum interrupter (VI) to a parallel capacitor and charge it up. In this way, a zero-crossing in the arc current can be achieved, and the current will be interrupted by the VI. Simulation results, which are supporting physical backgrounds for this analysis, have been presented in this paper while technological issues for industrial implementation of this concept have been discussed in detail. Full article

(This article belongs to the Special Issue Environmental Compatible Circuit Breaker Technologies)

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22 pages, 5509 KiB

Open AccessArticle

Breakdown at Multiple Protrusions in SF₆ and CO₂

by Odd Christian Feet, Martin Seeger, Daniel Over, Kaveh Niayesh and Frank Mauseth

Energies 2020, 13(17), 4449; https://doi.org/10.3390/en13174449 - 27 Aug 2020

Cited by 4 | Viewed by 2370

Abstract

The electric breakdown at single and multiple protrusions in SF₆ and CO₂ is investigated at 0.4 and 0.6 MPa, respectively. Additionally, the breakdown fields at rough surfaces of two different areas were determined. From the measurements, breakdown probability distributions for single [...] Read more.

The electric breakdown at single and multiple protrusions in SF₆ and CO₂ is investigated at 0.4 and 0.6 MPa, respectively. Additionally, the breakdown fields at rough surfaces of two different areas were determined. From the measurements, breakdown probability distributions for single protrusions were determined and fitted by Weibull distributions. This allowed the determination of statistical enlargement laws for the 50% breakdown probability fields E₅₀. Such enlargement laws describe, for example, the scaling of breakdown field with electrode area or number of protrusions. The predictions were compared to the experimental data, and both agreement and discrepancies were observed depending on polarity and number of protrusions and gas. Discharge predictions including first electron, streamer inception and crossing, as well as leader propagation, gave further insight to this. It was found that predictions from enlargement laws based on statistical processes may not describe the measured breakdown fields well and that relevant physical breakdown criteria must also be considered. Full article

(This article belongs to the Special Issue Environmental Compatible Circuit Breaker Technologies)

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17 pages, 5379 KiB

Open AccessArticle

Experimental Investigation of the Prestrike Characteristics of a Double-Break Vacuum Circuit Breaker under DC Voltages

by Yun Geng, Xiaofei Yao, Jinlong Dong, Xue Liu, Yingsan Geng, Zhiyuan Liu, Jing Peng and Ke Wang

Energies 2020, 13(12), 3217; https://doi.org/10.3390/en13123217 - 20 Jun 2020

Cited by 12 | Viewed by 2599

Abstract

The prestrike phenomenon in vacuum circuit breakers (VCBs) is interesting but complicated. Previous studies mainly focus on the prestrike phenomenon in single-break VCBs. However, experimental work on prestrike characteristics of double-break VCBs cannot be found in literature. This paper aims to experimentally determine [...] Read more.

The prestrike phenomenon in vacuum circuit breakers (VCBs) is interesting but complicated. Previous studies mainly focus on the prestrike phenomenon in single-break VCBs. However, experimental work on prestrike characteristics of double-break VCBs cannot be found in literature. This paper aims to experimentally determine the probabilistic characteristics of prestrike gaps in a double-break VCB consisting of two commercial vacuum interrupters (VIs) in series under direct current (DC) voltages. As a benchmark, single-break prestrike gaps were measured by short-circuiting one of the VIs in a double break. The experimental results show that the 50% prestrike gap d₅₀ of each VI in a double break, which is calculated with the complementary Weibull distribution, was significantly reduced by 25% to 72.7% compared with that in a single break. Due to the voltage-sharing effect in the double-break VCB, scatters in prestrike gaps of each VI in a double break was smaller than that in a single break. However, without the sharing-voltage effect, d₅₀ of the low-voltage side in the double break was 65% higher than that of the same VI in the single break, which could be caused by the asynchronous property of mechanical actuators, the difference of the inherent prestrike characteristics of each VI and the unequal voltage-sharing ratio of VIs. Full article

(This article belongs to the Special Issue Environmental Compatible Circuit Breaker Technologies)

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