High Arcing Research Articles

Benefit of Modern Arc Management in MF Dual Magnetron Sputtering Power Supplies

For modern large area coatings reactive dual magnetron sputtering (DMS) is a widespread technology. Economic constraints and advanced technology calls for increasing process flexibility regarding target utilization as well as the use of new materials. This in turn raises demands to the arc handling capabilities of the power supplies. On the one hand, a stable process at high arcing rates demands short arc blanking times and fast recovery to full output power. On the other hand, some materials tend to the formation of so-called “hard” arcs, with hot cathode spots. In this case, longer treatment times are needed. The benefit of modern arc handling capabilities is demonstrated for reactive SiO2 deposition from heavily used targets. For other demanding materials with low melting point, favourable operating modes are investigated.

Arc characteristics and metal transfer behavior of CMT + P welding process

The cold metal transfer (CMT) with addition of pulses (CMT+P) process is a new CMT welding method. The CMT+P transfer mode is a combination of a projected transfer mode with one droplet per pulse and a short circuit transfer mode during the cold metal transfer period. The results indicate that the current and voltage waveforms of the CMT+P welding process were quite different from those of the traditional CMT process. The appearance of the high initial arcing current and the current pulse steps as well as the low current for the pulse time phase for the first CMT period indicate a stable, smooth CMT+P transfer process. The high pulse current of the CMT+P process results in a higher heat input compared to the CMT process. A greater penetration and contact angle of the weld bead can be obtained by increasing the pulse number.

Transient selectivity for enhancing autonomous fault management in unearthed distribution networks with DFIG-based distributed generations

This paper proposes a method for identifying the faulty section in unearthed distribution networks connected with Doubly-Fed Induction Generator (DFIG)-based distributed generation. The proposed method depends on a dedicated transient-based selectivity function that is incorporated in an autonomous fault management procedure. Faulty section discrimination is performed by extracting the relative polarities of the front slopes at the terminals of each section generated by the fault current. The integration procedure of the protection selectivity function with the autonomous control is designed for the unearthed MV networks. Both earth and phase faults are considered in order to realize a broad, versatile and practical classification for such networks. Simulation cases are prepared using the ATP-EMTP package for testing purposes. The results corroborate the efficacy of the proposed method for classifying the faulty segment in distribution networks even for high impedance arcing faults as well as with considerable amounts of distributed wind turbines.

A method to predict possibility of arcing in EDM of TiB2p reinforced ferrous matrix composite

Electrical Discharge Machining (EDM) is very popular for machining conductive metal matrix composites (MMCs) because the hardness rendered by the ceramic reinforcements to these composites causes very high tool wear and cutting forces in conventional machining processes. EDM requires selection of a number of parameters for desirable results. Inappropriate parameter selection can lead to high overcuts, tool wear, excessive roughness, and arcing during machining and adversely affect machining quality. Arcing leads to short circuit gap conditions resulting in large energy discharges and uncontrolled machining. Arcing is a detrimental phenomenon in EDM which causes spoiling of workpiece and tool electrode and tends to damage the power supply of EDM machine. Parameter combinations that lead to arcing during machining have to be identified and avoided for every tool, work material, and dielectric combination. Proper selection of parameter combinations to avoid arcing is essential in EDM. In the work, experiments were conducted using L27 design of experiment to determine the parameter settings which cause arcing in EDM machining of TiB2p reinforced ferrous matrix composite. Important EDM process parameters were selected in roughing, intermediate, and finishing range so as to study the occurrence of arcing. Using the experimental data, an artificial neural network (ANN) model was developed as a tool to predict the possibility of arcing for selected parameter combinations. This model can help avoid the parameter combinations which can lead to arcing during actual machining using EDM. The ANN model was validated by conducting validation experiments to ensure that it can work accurately as a predicting tool to know beforehand whether the selected parameters will lead to arcing during actual machining using EDM. Validation results show that the ANN model developed can predict arcing possibility accurately when the depth of machining is included as input variable for the model.

Ultra-high voltage capillary electrophoresis >300 kV: Recent advances in instrumentation and analyte detection

Instrumentation has been developed for the implementation of ultra-high voltage capillary electrophoresis (UHVCE) with potentials up to and exceeding 300kV. Several separations have been used to demonstrate the utility of higher applied voltages for improving the resolution of peptide, protein, and nucleic acid separations. Previously reported instrumentation was limited to 120kV and required submersion in a bath of transformer oil to prevent corona and high voltage arcing between the components of the instrument [Hutterer, 1999, 2000, 2005] [1–3]. A modular design that uses plastic dielectric materials to overcome these obstacles enabling simplified operation of the instrument in air is described here in detail. A forced air system developed to control the temperature of the instrument to within a few degrees over a range of 25–60°C for use with ultra-high voltage capillary gel electrophoresis is also described. UHVCE instrumentation and its applications with UV absorption and laser induced fluorescence detection are further developed, and the first demonstration of UHVCE coupled to electrospray ionization-mass spectrometry is shown.

Reducing Arc-Flash Risk

This article analyzes methods to reduce the exposure of personnel to high energy arcing faults to levels below 40 cal/cm and also defines a method to determine the limits of coordination among protective devices to identify where the selectivity could be jeopardized.

Performance of the Scattering Matrix Arc Detection System on the JET ITER-like ICRF antenna

Ion Cyclotron Radio Frequency (ICRF) antennas operating under high voltage to couple high power to fusion plasmas are at risk of electrical arcing. The standard Voltage Standing Wave Ratio (VSWR) system does not protect low impedance areas, which are used in antennas to achieve load tolerance to variations in plasma loading during Edge Localised Modes (ELMs). The Scattering Matrix Arc Detection System (SMAD) was designed to create additional protection for these areas, and 4 complete systems were implemented and tested on the ITER-like antenna (ILA) on JET. This paper describes the performance under relevant experimental conditions of load tolerance and/or high voltage and electrical arcing causing generator trip events.

Gigawatt power microwave devices and vacuum

Low pressure breakdown is a major concern for developing high power microwave (HPM) devices, especially when going to more compact designs and to extreme powers, typically cm-size gaps in the tube and GW level output. In connection with the vacuum quality, we will consider the general aspects which may contribute to limit the operation of a HPM device: high voltage arcing, electrode erosion and degassing, rf breakdown in the cavities, surface breakdown at the windows, repetition rate. Vacuum measurement and electromagnetic compatibility with vacuum equipment will be treated too. As an example, we will consider in details the development of a compact magnetically insulated line oscillator (MILO) operating successfully at the Gigawatt level in the S-band.

MEMS-based power disconnect for <inline-formula><math display="inline" overflow="scroll"><mrow><mn>42</mn><mtext>-</mtext><mi mathvariant="normal">V</mi></mrow></math></inline-formula> automotive power systems

We present the design of a micro-electro-mechanical-system(MEMS)-based power disconnect for use with the proposed 42-V automotive power systems. High-voltage power systems are prone to arcing, which occurs during power disconnections. The high arcing current may lead to severe damage on the systems and may expose electric shock hazards to humans. The objective of the MEMS-based power disconnect we propose is to eliminate arcing occurrence in the systems. To eliminate arcing, one alternative is to electronically terminate the power supply to the system prior to the physical disconnection. The integrated MEMS force sensor on the power disconnect will be activated as a service technician disconnects the connector. The power supply to the system will be electronically shut off to prevent arcing during the physical interruption. The MEMS force sensor on the disconnect has an overall dimension of 3600 μm××1000 μm×10 μm and is fabricated with the Micragem fabrication process. A displacement reduction mechanism is incorporated into the sensor design to increase the sensitivity of the force sensor. Results show that the sensor is capable of measuring a maximum force input of 10.7 mN, resulting from a 20-μm displacement on the sensing structure.

Migration of Composite Contact Materials Components at High Current Arcing

The paper presents a method for testing transport of composite contacts materials under electrical arc conditions at high currents and for polarized electrodes. Tests and the discussion of results were carried out for silver-metal, silver-metal oxide and silver-tungsten carbide contact materials. Additionally, tungsten electrode was used as the second contact which was either cathode or anode. Spectrometric analysis of arc erosion components transported onto the second electrode and into the surroundings was carried out.

A novel selectivity technique for high impedance arcing fault detection in compensated MV networks

AbstractIn this paper, the initial transients due to arc reignitions associated with high impedance faults caused by leaning trees are extracted using discrete wavelet transform (DWT). In this way, the fault occurrence is localized. The feature extraction is carried out for the phase quantities corresponding to a band frequency 12.5–6.25 kHz. The detection security is enhanced because the DWT corresponds to the periodicity of these transients. The selectivity term of the faulty feeder is based on a novel technique, in which the power polarity is examined. This power is mathematically processed by multiplying the DWT detail coefficients of the phase voltage and current for each feeder. Its polarity identifies the faulty feeder. In order to reduce the computational burden of the technique, the extraction of the fault features from the residual components is examined. The same methodology of computing the power is considered by taking into account the residual voltage and current detail coefficients where the proposed algorithm performs best. Test cases provide evidence of the efficacy of the proposed technique. Copyright © 2007 John Wiley & Sons, Ltd.

Modeling and experimental verification of high impedance arcing fault in medium voltage networks

A high impedance arcing fault due to a leaning tree in medium voltage (MV) networks is modeled and experimentally verified. The fault is represented in two parts; an arc model and a high resistance. The arc is generated by a leaning tree towards the network conductor and the tree resistance limits the fault current. The arcing element is dynamically simulated using thermal equations. The arc model parameters and resistance values are determined using the experimental results. The fault behavior is simulated by the ATP/EMTP program, in which the arc model is realized using the universal arc representation. The experimental results have validated the system transient model. Discrete wavelet transform is used to extract the fault features and therefore localize the fault events. It is found that arc reignitions enhance fault detection when discrete wavelet transform is utilized

The influence of contacts erosion on the SF6 arc

In circuit breakers, high temperature arcing may lead to material erosion at the contacts. In this paper, numerical investigations have been performed in order to study the arc behaviours under the influence of copper vapours contamination in a simple Laval nozzle. The arc is assumed to be in local thermodynamic equilibrium. The erosion rate is estimated by considering the energy balance processes at the contact surface. Computations have been performed by a commercial computational fluids dynamics package (PHOENICS). The effects of contact polarity have also been investigated. It has been found that the presence of copper vapours cools down the arc temperature at the region close to the contacts. However, at current zero, the copper vapours concentration is very low. Post arc simulation has been performed in order to determine the critical rate of rise of recovery voltage (RRRV). Good agreement has been achieved with the experimental measurement of RRRV. It has been predicted that the contact erosion has a negligible effect on the interruption capability of the breaker.

Heating at Electrical Contacts: Characterizing the Effects of Torque, Contact Area, and Movement on the Temperature of Residential Receptacles

Testing was performed using 120 volt, 15-amp receptacles and copper wire to determine the effect of torque and wire contact area on temperature elevation at receptacle screw terminals. Torque was varied on both the hot and neutral terminals from 0 to 12 in-lbs, and the apparent wire contact at the screw terminal was varied by 1/8″ and 5/8″. There was no significant difference in temperature when changing apparent wire contact. Increased temperatures were observed with reduced torque, however, they were not significant enough to initiate a glowing connection, nor high enough to cause rapid oxidation. Further testing showed that movement of a loose connection was necessary to cause significantly high temperature changes, arcing and sparking, rapid oxidation, and in some cases, glowing connections.

Comparison of optimal low thrust ascent and descent trajectories for upper stages and planetary landers

Parallels may easily be drawn between powered ascent and descent from a planet without atmosphere. The lack of any explicit time dependence and no dissipative forces allows a simple time reversal. Departure from the Earth is complicated by the presence of the atmosphere. However, the upper stage phase of a multi-stage launcher shows similarities to ascent and descent from atmosphere-free planets. The use of relatively low thrust propulsion systems results in a more difficult problem, but when used for upper stages can ultimately yield payload advantages. Low thrust propulsion systems can also be used to advantage for planetary landers. This paper describes an efficient, multi-purpose optimisation technique used in the solution of these problems and compares the characteristics of solutions so obtained. The optimisation tool uses a direct multiple shooting method and variational calculus techniques for gradient calculation. The behaviour of an Earth departing upper stage is compared with landers on planets without atmosphere, such as Mercury. Optimisation of both classes of trajectories, when relatively low thrust engines are considered, shows a significant variation from more traditional, high thrust trajectories. In particular, high arcing phases are observed. This feature can also be seen in solutions of a simplified Pontryagin problem of minimum time ascent with low thrust, providing an insight into the nature of the full ascent and landing problems.

Discussion of "A novel fault detection technique of high impedance arcing faults in transmission lines using the wavelet transform"

The authors comment on the paper by C.-H. Kim et al. (see ibid., vol.17, p.921-9, 2002). They ask the authors to describe the circumstances for 154 kV system arcing faults. They also comment on the fault inception angle, wavelet selection, and the advantages of the wavelet transform in relation to its use.

Closure on "a novel fault detection technique of high impedance arcing faults in transmission lines using the wavelet transform"

The authors reply to the comments by A. Lazkano et al. (see ibid., vol.18, p.1596, 2003) on their original paper (see ibid., vol.17, p.921-9, 2002). They respond to all four points raised on the arcing faults, fault inception angle, and wavelet selection and use.

Dielectric recovery characteristics of a high current arcing gap

Experimental measurements of the dielectric breakdown strength of an arcing gap after current zero were made to determine the effects of arc chamber venting on the reverse recovery voltage needed to break down a recovering gap. The recovery conditions applied closely matched those created in a molded case circuit breaker under power line fault conditions. Three different vent sizes were used to determine the effect of gas pressure on the recovery characteristics of the plasma with recovery time between 170 /spl mu/s to 280 /spl mu/s, and currents from 3 kA/sub p/ to 15 kA/sub p/. Larger venting, providing increased cooling of the plasma, resulted in increased breakdown strength over the full range of currents. Based on the approximation that the recovering plasma breakdown strength is inversely proportional to plasma thermal temperature, breakdown voltage values were fitted to an exponential model to obtain plasma time constants and the initial hold-off voltage. Comparing these results to curve fits of E/p values showed E/p was a more accurate representation of the data. It is proposed to use E/p values when there is significant post current-zero chamber pressure. These results could be used as a guide to predicting molded case breaker interruption performance, especially for small arc chambers and short gaps.

Nonlinear behavior of 0-3 type ferroelectric composites with polymer matrices

The nonlinear electric and mechanical behavior of 0-3 type (particle-reinforced) ferroelectric composites with different viscoelastic and dielectric relaxation polymer-matrixes was observed experimentally. The analysis of the experimental results was carried out in the present study by examining the effects of the viscoelasticity and dielectric relaxation of the polymer matrices, the loading rate and the volume fraction of the PZT particles on the nonlinear behavior of the composites. The composite sample was isolated from the test frame to prevent high voltage arcing in the setup, which was employed to make precise measurement to systematically provide experimental results. Using a high voltage amplifier and a servo-hydraulic test frame, the hysteresis loops of electric displacement versus electric field at different loading amplitudes and rates, and the piezoelectric curves of the ferroelectric composites were measured. The results show that the effects of viscoelasticity and dielectric relaxation of the matrices on the electric and mechanical behavior of the ferroelectric composites are significant. The nonlinear behavior of ferroelectric composites with a viscoelastic and dielectric relaxation matrix is also related to the frequency of the applied loads.

Better interpretation of vacuum interruptor tests

In this article, we step through the development process, from fundamental investigations of the arc-contact interaction to performance and precertification testing of manufactured vacuum interrupters (VI). We also describe how VI models are tested above their arc-contact interaction to performance and rated current to monitor the quality of their materials and processing. The present work began with movies of arcs between spiral-type VI contacts, which generate a radial magnetic field to drive the high-current arc column along the spiral arms. The end-of-life condition of identical contacts and shields from manufactured VIs tested repeatedly under the corresponding conditions, was also systematically studied, along with the arc voltage traces. From the integration of these experimental results, guidelines have been developed for using the arc voltage waveforms of spiral-contact VIs to determine when in a high power arcing cycle the arc is stationary, moving, breaking up, diffuse or causing melting of the arc-contacts. In particular, anchoring of a high-current arc, and the resultant intense localized heating of the contacts, can increase the probability of long VI arcing times. Inspection of arc voltage traces is thus a method to monitor for contact damage and reduced internal performance during testing. The results are applicable to analysis of arc voltages and contact travel records from breaker certification tests.