Electrical Contact Testing Research Articles

Arc erosion behavior of Ag-8 wt.%ZrO2 contact materials with CuO additions

To clarify the effect of CuO on the arc erosion behavior of AgZrO2 contact materials, the Ag-8 wt.%ZrO2 contact materials without and with CuO addition were prepared by the combination of three-dimensional vibrating mixing and hot-pressing sintering, and the electrical contact tests were performed 5000 times on a JF04D electrical contact testing system. The effect of CuO additive on the arc erosion behavior of Ag-8 wt.%ZrO2 contact material was studied, and the arc erosion mechanism was discussed as well. The results show that an appropriate CuO addition can significantly improve the hardness, electrical conductivity and arc erosion resistance of Ag-8 wt.%ZrO2 contact material. At 0.5 wt%CuO, the optimal combination of relative density, hardness and electrical conductivity can be achieved, which are 99.48 %, 79.0 HV and 79.3 %IACS, respectively. Furthermore, the Ag-8 wt.%ZrO2 contact material with 0.5 wt%CuO addition exhibits the lowest arc energy and shortest arc duration, least mass loss, and silver splashing as well as the formation of pores are also significantly inhibited, displaying excellent arc erosion resistance. This can be ascribed to the improved electrical conductivity and enhanced interface bonding together with CuO decomposition under high temperature arc.

Arc erosion resistance of Al2O3–Cu/35Mo composites reinforced by trace graphene oxide

In this study, Al2O3–Cu/35Mo composites were prepared by rapid hot-press sintering-internal oxidation method, and the materials were modified by adding trace amounts of graphene oxide (GO). The results show that the relative densities of the composites are above 99%, the γ-Al2O3 generated by internal oxidation is diffusely distributed on the copper matrix. The incorporation of GO produced a small number of hard MoC particles at the interface, which facilitated the interfacial bonding of the composites. In the 30 V DC, 10–30 A electrical contact test, the anode mass of the composites increases, while the cathode mass decreases. And GO reduces the total mass loss of the electric contact by 63.6%, 38.9%, 51.3% and 20.9%, respectively. A comparison of the electrical contact properties of the two materials showed that the addition of GO dispersed the concentrated erosion of the arc. At 10 A and 30 A, the arc energy is reduced by 75.5% and 12.5%, respectively. With the gradual increase in electric current, GO makes the Al2O3–Cu/35Mo composites more stable during the electric contact process, improves the anti-welding ability of the contact and reduces contact resistance.

Simultaneously enhanced mechanical and electrical performance of Cu-10wt.%Mo contact material by the addition of graphite

To disclose the effect of graphite (G) addition on the mechanical and electrical performance of CuMo contact material, the Cu-10wt.%Mo contact materials without and with 1wt.%G addition were prepared by mechanical wet-mixing and spark plasma sintering. The electrical performances of the resultant materials were comparatively studied by electrical contact test under different currents, and the surface morphology and composition of the eroded electrodes were characterized by scanning electron microscope and energy dispersive spectrometer. As compared to the Cu-10wt.%Mo contact material, the hardness, tensile strength, flexural strength of Cu-10wt.%Mo-1wt.%G contact material are respectively increased by 33.7 %, 21.7 % and 9.7 %, while the electrical and thermal conductivity are only reduced by 2.3 % and 1.0 %, respectively. With increase of current, the Cu-10wt.%Mo-1wt.%G contact material presents lower make-arc-energy and shorter make-arc-duration with less fluctuations than the Cu-10wt.%Mo contact material without G addition. The average make-arc-energy and make-arc-duration of Cu-10wt.%Mo-1wt.%G contact material are decreased by 45.1 % and 62.6 %, respectively. Moreover, the addition of graphite remarkably alleviates the arc erosion. The total mass loss and relative transfer mass of the Cu-10wt.%Mo-1wt.%G contact material after 5000 operations are respectively reduced by 33.3 % and 14.3 % when compared with Cu-10wt.%Mo contact material. This can be ascribed to arc erosion preferentially occurred on the graphite with low work functions, and the released CO2 which promotes arc extinguishment. Furthermore, the addition of graphite increases the viscosity of the molten pool, restraining the splashing and evaporation of the molten Cu.

First-principles and experimental investigations on physical properties and arc erosion behavior of metal-doped AgSnO2 electrical contact materials

The effects of metal doping on the structural and physical properties of AgSnO2 contactors were investigated using simulations and experiments based on first-principles calculations. The electrical contact test system was tested for 20,000 electrical contacts to check the physical properties under 24 V/15 A DC resistive load and analyze the relationship between the parameters. The erosion morphology of the contact material was characterized by a 3D surface profilometer, and the mechanism of the molten pool force, material transfer, and arc erosion behavior was studied in detail. The results show that metal doping can improve the thermal stability, mechanical properties and electrical conductivity of the materials, and significantly affect the crystalline and electronic structure of the materials, resulting in better stability and resistance to arc erosion. The best arc erosion performance of AgSnO2–Y is related to its superior thermal stability and electrical properties, while the better arc erosion performance of AgSnO2–Cu is probably related to its good mechanical properties. In addition, metal doping has a significant effect on the arc formation and interruption of AgSnO2 contactors and leads to a change in the material transfer mode. This study provides a feasible method for the analysis of metal doping to improve the erosion performance of contact materials and provides a valuable reference for the further development of research on arc erosion resistance of contactors.

Fabrication and Arc Erosion Behavior of Ag-SnO2-ZnO Electrical Contact Materials.

This study investigated the synthesis of Ag-SnO2-ZnO by powder metallurgy methods and their subsequent electrical contact behavior. The pieces of Ag-SnO2-ZnO were prepared by ball milling and hot pressing. The arc erosion behavior of the material was evaluated using homemade equipment. The microstructure and phase evolution of the materials were investigated through X-ray diffraction, energy-dispersive spectroscopy and scanning electron microscopy. The results showed that, although the mass loss of the Ag-SnO2-ZnO composite (9.08 mg) during the electrical contact test was higher than that of the commercial Ag-CdO (1.42 mg), its electrical conductivity remained constant (26.9 ± 1.5% IACS). This fact would be related to the reaction of Zn2SnO4's formation on the material's surface via electric arc. This reaction would play an important role in controlling the surface segregation and subsequent loss of electrical conductivity of this type of composite, thus enabling the development of a new electrical contact material to replace the non-environmentally friendly Ag-CdO composite.

Arc erosion resistance of WC/CuCr30 composites based on changing of Cr particle morphology and orientation

CuCr30 composite was commonly applied in medium and low voltage vacuum interrupters. The WC/CuCr30 composites based on changing of Cr particle morphology and orientation were successfully prepared by vacuum hot press sintering and hot extrusion, and the arc erosion resistance behavior at different voltages along the deformation direction of Cr particles was investigated on the JF04C electrical contact material testing system. The microstructure characterization of WC/CuCr30 composites shows that the Cr particles in the WC/CuCr30 composite have been elongated and the long axis direction is close to parallel to the extrusion direction after the hot extrusion deformation. Compared with the longitudinal section, the thermal conductivity of CuCr30 and WC/CuCr30 composites in the cross section is increases by 3.75% and 3.63%, respectively. The electrical contact testing results under different voltages shows that the addition of WC particles can extend the service life of the CuCr30 composite, and the operation times of WC/CuCr30 composite (4850 times) increases by 34.72% compared to CuCr30 composite (3600 times) at 30 V DC. The welding force decreases more obviously with the increase of the voltage, and the average welding force of WC/CuCr30 composite decreases by 8.57% and 20.9% at 24 V DC and 30 V DC compared with CuCr30, respectively. The arc erosion mechanism analysis shows that addition of WC particles is beneficial for the decrease of arc duration. And WC particles can effectively inhibit the arc erosion process and delay the formation of bumps and pits.

Arc erosion behaviour of in-situ TiB2/Cu composites with a three-dimensional network structure

Copper matrix composites (CMCs) with tailored heterogeneous structures at the mesoscopic scale are promising candidates for electrical contact materials. In this work, CMCs reinforced by an in situ formed three-dimensional network of TiB2 particles were synthesized from Cu, Ti and B powder mixtures by reactive hot-pressing. The arc erosion behaviour of the fabricated CMCs was investigated by an electrical contact test. The distribution state of in situ TiB2 depends on the particle size of the Cu powder. The critical size for forming a continuous network in 3 wt%TiB2/Cu composites is estimated to be 24 μm. Once the continuous network is formed in CMCs, the arc energy and duration suddenly change to ultrasmall and stable values, and the erosion area and total mass loss after 5000 cycles of the contact test remarkably decrease. The results indicate that the CMCs reinforced by in situ networks of TiB2 particles exhibit excellent arc erosion resistance.

Characteristics and GWO–ANN Model Based on Prior Knowledge for Contact Resistance in a Pantograph–Catenary

The current-collection performance of a pantograph–catenary directly influences the safe operation of high-speed electric locomotives. The contact resistance is a primary indicator to evaluate the stability and reliability of the current-collection performance. The effects of sliding speed and electric current on the contact resistance between the carbon strip and the contact wire under a dynamic pressure load were studied using a sliding electrical contact testing machine. To predict the contact resistance under various working conditions, an artificial neural network (ANN) regression model, based on the gray wolf optimizer (GWO) algorithm and prior knowledge, was developed. The GWO algorithm was used to optimize the initial biases and weights of the ANN to avoid becoming trapped in local optima. The performance of the GWO–ANN can be further enhanced by the use of prior knowledge. The results showed that the GWO–ANN model that included prior knowledge can be introduced as a new technique for estimating the contact resistance in pantograph–catenary systems.

Effect of in situ graphene-doped nano-CeO2 on microstructure and electrical contact properties of Cu30Cr10W contacts

Abstract The graphene oxide (GO)-doped nano-CeO2 was introduced into Cu30Cr10W electrical contact composites by ball milling dispersion, freeze-drying, and spark plasma sintering, resulting in excellent mechanical strength and high arc erosion resistance. The effects of GO and CeO2 on the microstructure and properties of the composites were investigated. The arc erosion behavior was investigated by the JF04C electrical contact testing apparatus. Consequently, the uniform distribution of CeO2 nanoparticles hinders the movement of dislocations, GO transformed into reduced graphene oxide (rGO) during high-temperature sintering, and the in situ formation of Cr3C2 between trace carbon atoms and chromium particles at the C–Cu interface, which enhanced the interface combination. Compared with Cu30Cr10W composites, the tensile strength of the two composites was increased by 47 and 36% by importing GO and nano-CeO2, respectively. Finally, electrode material migrated from the cathode to the anode, and the rGO delayed the formation of pits and sharp bumps on the contact surface of the electrode and inhibited diffusion of molten metal; when compared with Cu30Cr10W, the GO/CeO2–Cu30Cr10W composites have better welding force.

Arc erosion resistance of hybrid copper matrix composites reinforced with CNTs and micro-TiB2 particles

Synergistic strengthening is increasingly explored for developing high-performance copper matrix composite. In this work, the hybrid copper matrix composites reinforced with carbon nanotubes (CNTs) and micro- TiB2 particles（（CNTs-TiB2）/Cu composites）were prepared by electroless copper plating, powder metallurgy and hot extrusion. The arc erosion resistance of the hybrid copper matrix composites was studied in JF04C electrical contact testing system. And the synergistic effect of CNTs and TiB2 particles in different content ratios on the arc erosion resistance of composites was analyzed emphatically. The action mechanism of CNTs and TiB2 particles in arc erosion process is discussed in detail. Results show that the arc duration and arc energy of the hybrid copper matrix composites are lower than that of copper matrix composites single reinforced with CNTs or TiB2 particles. When the volume fraction of CNTs is 4.2% (The content of TiB2 particles is 1.6%), the arc erosion resistance of the hybrid copper matrix composites is optimal. In arc erosion process, CNTs can form a network structure parallel to the extrusion direction in copper matrix, and the continuous CNTs network structure can effectively disperse cathode arc, promote arc movement, increase work function of copper matrix composites, inhibit electron emission and reduce total emission current density. And the micro- TiB2 particles are helpful to improve the viscosity of molten pool, which can reduce the material mass loss and erosion pit on the surface of composites. Under the combined actions of CNTs and TiB2 particles (4.2CNTs-1.6TiB2)/Cu composite presents better arc erosion resistance stability, lower arc duration and energy.

Electrical contact performance of various electro-deposited graphene reinforced silver-based nanocomposites

Abstract Silver and silver(Ag)-graphene(Gr) nanocomposite coatings were prepared via direct current, pulse current and pulse reverse current on copper electrical contacts for evaluating electrical contact performance. The effects of the addition of Gr and current types on microstructure, crystallographic orientation, mechanical properties and electrical contact performance were investigataed via a scanning electron microscope, an X-Ray diffractometer, microhardness test device and an electrical contact test device, respectively. The addition of Gr changed the Ag surface morphology and decreased grain sizes. Moreover, the addition of Gr significantly improved arc erosion resistivity and decreased the average working temperature during the contact test. In addition, pulse current and pulse reverse current provided a significant improvement in microhardness and electrical contact erosion resistance owing to increased embedded graphene amounts in silver layers.

Investigation of Arc Erosion Mechanism for Tin Dioxide-Reinforced Silver-Based Electrical Contact Material Under Direct Current

To get an in-depth insight into the arc erosion mechanism for tin dioxide-reinforced silver-based (Ag-SnO2) contact material, the contact pairs made of Ag-4wt%SnO2 contact material were, respectively, performed for 20,000 switching operations under the direct currents of 19 A and 29 A and the voltage of 12 V, together with the electrode gap of 4 mm. The eroded surfaces and cross-sectional morphologies and the chemical compositions were characterized by scanning electron microscopy equipped with an energy dispersive spectrometer (EDS). The results show that there is a deep erosion pit at the cathode and an apparent protrusion at the anode, suggesting that a serious material transfer generates from cathode to anode. The EDS results show that the Sn contents at the protrusion and at the region around the crater are below 0.75 wt.% and 4 wt.%, respectively. This reveals that SnO2 undergoes severe evaporation during electrical contact testing. Moreover, arc stability decreases with increasing the load current, and the Ag-SnO2 contact material has larger arc power (make arc: 68.2 J/s; break arc: 58.53 J/s at 29 A) as compared to Ag-TiB2 contact material (make arc: 62.85 J/s; break arc: 50.01 J/s at 29 A). As a result, it is thought that SnO2 evaporation reduces Ag dissipation, thus shortening the lasting time of the make arc. However, the emission current is increased owing to the low work function of SnO2, which further promotes the improvement in the density of the charged particles, thereby enhancing the arc power. Additionally, the large density of charged particles can sustain arc burning for a longer time, resulting in an extended break arc duration.

Electrical contact performance of various electro-deposited graphene reinforced silver-based nanocomposites

Abstract Silver and silver(Ag)-graphene(Gr) nanocomposite coatings were prepared via direct current, pulse current and pulse reverse current on copper electrical contacts for evaluating electrical contact performance. The effects of the addition of Gr and current types on microstructure, crystallographic orientation, mechanical properties and electrical contact performance were investigataed via a scanning electron microscope, an X-Ray diffractometer, microhardness test device and an electrical contact test device, respectively. The addition of Gr changed the Ag surface morphology and decreased grain sizes. Moreover, the addition of Gr significantly improved arc erosion resistivity and decreased the average working temperature during the contact test. In addition, pulse current and pulse reverse current provided a significant improvement in microhardness and electrical contact erosion resistance owing to increased embedded graphene amounts in silver layers.

Effect of Ni addition on the arc-erosion behavior of Ag-4 wt.%SnO2 electrical contact material

To disclose the effect of Ni addition on the arc-erosion behavior of Ag-4 wt.%SnO2 contact material, the Ag-4 wt.%SnO2 contact materials with and without 4 wt%Ni were comparatively studied. The sintered materials were examined by scanning electron microscopy and transmission electron microscopy. The electrical contact tests were performed for different operations on an electrical contact testing system. The eroded morphology evolution and ingredients of the electrical contact surface under the action of arc were characterized, and the mass loss and welding behavior were studied as well. The results show that the Ag-4 wt.%SnO2 contact material has large break-arc-energy, which aggravates the SnO2 evaporation or decomposition. The reduced SnO2 content further decreases the arc erosion resistance and, in turn, causes much serious arc erosion, thereby resulting in larger mass loss and serious welding. However, for the Ag-4 wt.%SnO2-4 wt.%Ni contact material, Ni addition reduces the evaporation and decomposition of SnO2 due to its high melting point and poor thermal conductivity. Additionally, the reiterative dissolution and precipitation of Ag and Ni under the action of arc lead to the formation of fine precipitation phase, which is beneficial for the arc dispersion and generation of stable arc. As a consequence, the evaporation, splash, mass loss and welding are decreased, and the arc erosion resistance is significantly improved.

Graphene oxide effects on the properties of Al2O3-Cu/35W5Cr composite

Graphene oxide (GO) nanosheets were dispersed into premixed powders (Cu-0.4 wt% Al/35W5Cr) by wet grinding and vacuum freeze-drying process. The 0.3 wt% GO/Al2O3-Cu/35W5Cr and 0.5 wt%GO/Al2O3-Cu/35W5Cr composites, used for electrical contacts, were fabricated by vacuum hot-pressing sintering. The microstructure was analyzed by field emission scanning electron and transmission electron microscopy. In addition, the Raman spectroscopy and X-ray photoelectron spectroscopy were used to investigate the structural changes of GO before and after sintering. The arc erosion behavior was investigated by the JF04C electrical contact testing apparatus. Consequently, the Al2O3 nanoparticles were evenly dispersed in the matrix, causing dislocation tangles. GO was converted to reduced graphene oxide after sintering. A group of carbon atoms combined with Cr forming Cr3C2 in situ during sintering, which enhanced the interface bonding. Compared with the Al2O3-Cu/35W5Cr composite, the tensile strength of the two contact materials containing 0.3 wt% GO and 0.5 wt% GO was increased by 45% and 34%, respectively. Finally, pips and craters were present on the anode and cathode surfaces, respectively. Tungsten has undergone re-sintering during arcing and formed needle-like structures. Compared with Al2O3-Cu/35W5Cr, the GO/Al2O3-Cu35W5Cr composites have better welding resistance. The final mass transfer direction of the two composites was from the cathode to anode.

Study on Electrical Properties of AgSnO2 Contact Materials Doped With Rare-Earth La, Ce, and Y

The proposed method is based on the first principles of density functional theory to calculate the electronic structure of SnO2 and rare-earth elements-doped SnO2. The energy band and density of state of undoped SnO2 and SnO2-X (La, Ce, and Y) are calculated and apply Origin Pro 9.0 for quantitative calculation. Conducting experimental verification of AgSnO2 and AgSnO2-X (La, Ce, and Y), contact materials prepared by sol–gel and powder metallurgy methods and the contact resistance and arcing energy are measured by the simulated electrical contact test. In the simulation results of SnO2-X (La, Ce, and Y), the relative electrical conductivity of Y-doped SnO2 is the largest. In the experimental results, the minimum and maximum values and the range of the variation of the arc energy and contact resistance after AgSnO2-X (La, Ce, and Y) are reduced. The effect of Y-doped AgSnO2 is more obvious and has the highest density. The final simulation and experimental results can be well matched. The best electrical performance is Y-doped AgSnO2, followed by La-doped AgSnO2.

Arc erosion behavior of the Al2O3-Cu/(W, Cr) electrical contacts

Al2O3-Cu/(25)W(5)Cr and Al2O3-Cu/(35)W(5)Cr electrical contact materials were fabricated by vacuum hot-pressing sintering and internal oxidation. The relative density, electrical conductivity, and Brinell hardness were measured. The microstructure was analyzed by scanning electron microscopy and transmission electron microscopy. JF04C electrical contact testing apparatus were used to investigate the electrical contact performance of composites. Arc erosion morphologies were analyzed by scanning electron microscopy and three-dimensional profilometer. The material transfer as well as electrical contact performance were studied during contact make and break operations at 30 V DC with current between 10 and 30 A. It indicates that the nano-Al2O3 particles pinned dislocations. Material transfers from the cathode to the anode. With the melting, evaporation, and sputtering of Cu during arcing, W particles gather and generate needle-shaped skeletons. Finally, liquid droplets, needle-like structures, craters, and bulges were formed on electrode surfaces after arc erosion. Furthermore, their quantity and morphology are affected by tungsten content. When the content of W in the dispersed copper matrix increases from 25 wt% to 35 wt%, welding force is reduced during the steady operations. In addition, when the arc duration is greater than 8.86 ms, the Al2O3-Cu/(35)W(5)Cr contact material has a shorter average arc duration than Al2O3-Cu/(25)W(5)Cr at the same arc energy.

Influence of WO3 addition on the material transfer behavior of the AgTiB2 contact material

To clarify the effect of WO3 addition on the electrical performance of Ag-4wt.%TiB2 contact material, each contact pair was made 20,000 operations at 12 V, 29 A for the Ag-4wt.%TiB2 contact materials without and with WO3 addition. The morphology and chemical composition of arc eroded contact surface were characterized by scanning electron microscope and energy dispersive spectrometer, and the mass change before and after electrical contact test was determined as well. The results show that WO3 addition not only decreases the arc duration and arc energy, but also changes the arc erosion characteristics and material transfer mode. For the Ag-4wt.%TiB2 contact material without WO3 addition, the material transfer occurs from cathode to anode. However, it has an opposite change for the Ag-4wt.%TiB2 contact material with WO3 addition. Furthermore, WO3 addition can prevent the formation of cracks on the eroded surface.

Effect of strengthening phase on material transfer behavior of Ag-based contact materials under different voltages

To clarify the correlation of strengthening phase and particle sizes with the material transfer behavior for Ag-based contact materials, the Ag-4wt%TiB2 and Ag-4wt%SnO2 contact materials reinforced with different TiB2 and SnO2 particles were prepared, and the electrical contact tests were up to 5000 operations at different voltages. The surface morphologies of arc-eroded specimens were characterized by scanning electron microscope, the mass changes before and after electrical contact test were determined, and the material transfer behavior of Ag-4wt%TiB2 and Ag-4wt%SnO2 contact materials at different voltages were discussed as well. The results indicate that the voltage has a significant effect on make arc and break arc, which leads to the change of the material transfer mode. Furthermore, the strengthening phase remarkably influence the electrical performances of Ag-based contact materials. The Ag-4wt%TiB2 contact material presents higher make-arc-energy and lower break-arc-energy than the Ag-4wt%SnO2 contact material. The fine strengthening particles are beneficial for the decrease of arc energy. Subsequently, the Ag-based contact material prepared with fine strengthening particles has less material transfer and mass loss.

차단키 실패 보호 IED의 IEC 61850 시스템 성능 시험 절차서에 관한 연구

Korea Electric Power Research Institute in charge of the power IT project Development of Prototype for Advanced Substation Automation System based on the Digital Control Technology is performing system verification. Breaker Failure protection IED can operate protection activity by communicating with other IEDs such as T/L IED, owing to IEC 61850 international standard and digital substation automation system. Accordingly, IED testing process should be changed from the conventional way by electrical contact test on individual IED to system based testing method by network communication. This paper describes how to test BF IED based on substation automation system and testing procedures using UML, which is used to implement S/W design.