Breaking Capacity Research Articles

Development of a fuse digital model for virtual testing of breaking capacity

Development of a fuse digital model for virtual testing of breaking capacity

Study on the vacuum arc characteristics between novel straight slot transverse magnetic contacts with auxiliary slots on the back

The motion stability of the vacuum arc between TMF contacts significantly affects the breaking capacity of vacuum switches. The vacuum arc movement can be effectively controlled by slots on the TMF contacts to provide the necessary driving force. However, the necessary cross-slot movement of the arc affects its stability. In this paper, a novel straight-slot transverse magnetic field (SSTMF) contact structure with additional auxiliary slots on the back is proposed to improve current distribution and avoid stagnation at the contact center. The simulation analysis was conducted on the force acting on the arc at different positions and the magnetic field distribution between the contacts. Additionally, the arcing experiments were performed in a demountable vacuum chamber for both novel and traditional SSTMF contacts. The SEM analyses were carried out for the contacts after the experiments. Combined with simulation and comparative experimental results, it is verified that the auxiliary slots can improve the control and driving effect on the arc. This can provide ideas and references for future contact design and improve the breaking performance of vacuum circuit breakers.

Influence of different factors on gap breakdown process with hot electrode and high temperature gas medium in low voltage circuit breaker chamber based on particle-in-cell/Monte-Carlo collision simulation

Different factors such as gas composition inside the low voltage circuit breaker (LVCB) chamber and the residual plasma in the post-arc stage affect the breakdown process, which in turn affects the breaking capacity of LVCBs. In this paper, the effects of non-parallel electrode structure, gas temperature and pressure, electrode temperature, and gap distance on gap breakdown of hot electrode under high temperature gas conditions were studied, for which a particle-in-cell/Monte-Carlo collision simulation model has been established, which takes into account the effects of high-temperature gas components, cathode electron thermal emission, electron collision ionization and other effects, and simulation studies have been conducted. The simulation results show that the increase in gap gas temperature, the decrease in air pressure, and the increase in electrode temperature will lead to the gap breakdown more easily. With the increase in the gap length, the breakdown voltage increases, but the average electric field intensity required for breakdown decreases. In the non-parallel electrode structure, the breakdown occurs first at the position with the shortest gap distance, then the cathode sheath forms and extends along the electrode surface to other areas, and finally, the entire gap breaks down.

Improved assembly DC circuit breaker based on resonant current injection.

DC circuit breakers (DCCBs) with high breaking capacity and low cost are necessary for quick fault clearance in DC networks. The assembly DC circuit breakers (ADCCBs) have a main breaking section (MBS) and a sub-breaking sections (SBS) for each line, which greatly reduce the cost. But in conventional operation, it bears high voltage for a long time when there is a main switch grounding process in any line fault action. To address this problem, a multiport assembly circuit breaker based on current injection (CI-MPACB) is proposed, which is able to generate a resonant current with increasing amplitude by controlling the duty cycle of Integrated Gate-Commutated Thyristors (IGCTs). Then the resonant current is injected into the SBS to generate current zero crossing and arc extinction. A complex frequency domain circuit analysis is performed on the MBS to describe the action logic as well as the commutation characteristics. In addition, the parameters of each component of the MBS are subject to multiple constraints and reasonable design to ensure the fault current could be cut off quickly and reliably. The cost of existing design is greatly reduced due to the design idea of resonant current injection device parameter selection. Finally, a PSCAD/EMTDC simulation confirms the opening viability of CI-MPACB and the accuracy of the parameter design. The test results show that the designed CI-MPACB can cut off DC fault lines.

First‐Principles Calculations of Material Properties of CuCrZr Alloy Contacts

CuCrZr alloy is widely used in vacuum circuit breaker contact materials and high‐speed railroad contact wires, etc. The study of the effect of different Cr and Zr contents on the performance of CuCrZr alloy is of great significance for the improvement of circuit breaker's breaking capacity, as well as the load and structural stability under harsh working conditions. In this paper, the mechanical properties, electronic density of states and thermodynamic properties of CuCrZr solid solution alloys randomly doped by different concentrations of Cr and Zr are comparatively analyzed using first‐principles calculations based on density functional theory. The results show that the alloys with different doping compositions have strong mechanical stability, electrical conductivity, and thermomechanical stability, and the reduction of the Cr/Zr doping concentration ratio can improve the toughness and ductility of the alloys, and the solid solution alloy with the composition of CuCr0.06Zr0.19 has the best machinability. The doping of Cr and Zr can improve the thermal stability of the alloy, Cr and Zr can be used as high‐temperature toughening elements for Cu. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

An analysis of circuit breaker capacity according to IEC 60909 and IEC 60059 standards at the PT Borneo Alumina Indonesia electrical system

At PT Borneo Alumina Indonesia (PT BAI), the D01 Power Distribution System uses circuit breakers (CB) with a current rating capacity of 1250A for both incoming and outgoing 10kV busbars. Replacing outgoing CBs with the same capacity during maintenance leads to unnecessary waste. This study was conducted to examine the appropriate CB capacity as a substitute for the old CBs in the outgoing 10 kV busbars for loads of 10 kV induction motors and transformers so that recommendations can be made to improve efficiency during maintenance on the D01 Power Distribution System. The Electronic Transient Analyzer Program (ETAP) 19.0.1 software was used to perform short circuit simulations based on IEC 60909 and load flow simulations, which were then adjusted to IEC 60059 and CB products from Siemens. The results show that we can replace the current Siemens CB, which has a rated breaking current specification of 31.5kA, with 25kA during the maintenance period. We can also replace the rated peak value of 80kA with 63kA, and the rated current of 1250A with 630A. Replacement of CB specifications does not change/modify the switchgear panel because the replacement CB matches the brand, dimensions, and size of the currently installed CB. These findings would also help increase efficiency during maintenance on the D01 Power Distribution System. The discussion includes limitations and recommendations for future research.

Efficient hydrodeoxygenation of methyl palmitate over NiMo/ZrO2 catalyst with electron transfer between Ni and Mo

The hydrodeoxygenation of biomass into high quality fuels is one of the effective technologies to produce green diesel and solve the environmental pollution of fossil fuels at source. In this work, the catalytic performances of NixMoy/ZrO2 catalysts for methyl palmitate hydrodeoxygenation were evaluated, and the characterization results were combined to understand their role of physicochemical and structural properties in modulating the specific selectivity of alkanes. Under mild reaction condition (270 °C, 3 MPa), the Ni1Mo1/ZrO2 catalyst showed the best hydrodeoxygenation reactivity (conversion: 99.4%) and alkane selectivity (95.0%, hexadecane: 73.6%) of methyl palmitate. It was found that the electron transfer from Mo to Ni in Ni1Mo1/ZrO2 catalyst promoted the active site Ni anchoring and H2 molecules activation, which were associated with the better hydrodeoxygenation activity. In addition, the highest oxygen vacancies and Mo5+ content in Ni1Mo1/ZrO2 catalyst benefited the adsorption and breaking capacity of CO/C-O bonds and hexadecane yield. The Ni1Mo1/ZrO2 catalyst maintained excellent catalytic performance and structural stability after a long-term test of 60 h, which could be efficiently applied for hydrodeoxygenation of methyl palmitate.

Performance evaluation of a power-operated garlic (Allium sativum L.) bulb breaker for clove separation

Garlic (Allium Sativum L.) is a valuable root crop that can be utilized to season foods and is widely utilized in Ethiopia to treat many different kinds of diseases. The cloves are separated by hand for plantation and processing functions. This technique can be very exhausting and take a lot of time. To fill this gap, a garlic bulb-breaking machine was fabricated and tested with the clove variety grown in Holeta, Ethiopia. The major component of the machine is two rollers that revolve in opposing directions, and shearing the bulbs to separate the cloves. The performance test experiments were carried out in a full factorial design with feed rate as the first factor having three levels (3.7, 4.2, and 5.2 kg/min) and roller speed as a second factor with also three levels (276, 326, and 376 rpm). All tests were done at 66 % moisture content of garlic and 19 mm clearance between the breaking rollers. The interaction effect of the two factors shows an important difference (p < 0.05) in machine performance. The maximum breaking efficiency of (87.05 %) occurred at a feed rate (4.2 kg/min) and roller speed (326 rpm). Likewise, the maximum breaking capacity (306.98 kg/h) was recorded for the highest (5.2 kg/min) feed rate regardless of the 276 rpm roller speed. The minimum clumps of cloves (10.27 %) were obtained at combinations of 4.2 kg/min and 326 rpm. The lowest values of damaged cloves (1.79 %) and fuel consumption (5.61 ml/kg) were observed for the combination of the 3.7 kg/min with the 276.85 rpm whereas the maximum clove damage (2.29 %) was at the 5.2 kg/min feed rate combined with the maximum roller speeds (376 rpm). Therefore, the machine could be operated at the combination of 4.2 kg/min and 326 rpm for best performance in the majority of the parameters.

Graphene-Enhanced CuW Composites for High-Voltage Circuit Breaker Electrical Contacts

To address the issue of over-standard short-circuit currents in a power system, it is imperative to enhance the comprehensive performance of the electrical contacts, which serve as the lynchpin of circuit breakers, so as to improve the breaking capacity of high-voltage circuit breakers. Graphene, as the most prominent two-dimensional carbon material in recent years, has garnered widespread applications across various fields. In this study, graphene-enhanced CuW composites for high-voltage circuit breaker electrical contacts were prepared innovatively using integrated vacuum infiltration technology. The innovative graphene-enhanced CuW composites significantly improved the mechanical, electrical, and ablation resistance properties, and have been successfully applied in the 252 kV/63 kA high-voltage SF6 circuit breakers, achieving 20 times effective consecutive full-capacity short-circuit current breaking. It provides a new route for the development and application of high-performance CuW electrical contacts. Looking ahead, it is planned to extend their application to higher voltage grade high-voltage circuit breakers.

Particle-in-cell/Monte Carlo collision simulation on gap breakdown characteristics of under the conditions of hot-electrode and high-temperature gas medium in low-voltage circuit breaker chamber

The gas composition inside the low-voltage circuit breaker (LVCB) chamber and the residual plasma in the post-arc stage affect the breakdown process, which in turn affects the breaking capacity of LVCBs. In this paper, the back-arc breakdown and post-arc re-breakdown phenomena occurring inside the LVCB chamber are categorized as the breakdown in the case of high-temperature gas gap of hot electrodes, for which a particle-in-cell/Monte Carlo collision simulation model has been established, which takes into account the effects of high-temperature gas components, cathode electron thermal emission, electron collision ionization, and other effects, and simulation studies have been conducted. The simulation results show that the gap breakdown is mainly caused by the high-temperature hot free background gas and the cathode thermal electron emission. A plasma sheath layer is formed at the cathode during the breakdown process, and the electric field strength in the sheath layer is higher than that in other regions. With the development of the streamer to the cathode, the thickness of the sheath layer becomes narrower and the electric field strength increases, and finally, a discharge plasma channel is formed in the gap.

Influence of pick blunting on hydraulic breaker capacity in fracture of granite blocks

Influence of pick blunting on hydraulic breaker capacity in fracture of granite blocks

ОГЛЯД ПРИНЦИПІВ СЕЛЕКТИВНОСТІ ЗАХИСТІВ В РОЗПОДІЛЬЧИХ МЕРЕЖАХ СПОЖИВАЧІВ НАПРУГОЮ 0,4 кВ

The analysis of existing principles of selectivity indicates the complexity and incompleteness of ensuring the coordination of the operation of protection devices in distribution networks of 0.4 kV consumers. Current selectivity is ensured only in the area of action of short-circuit currents. To ensure it, electromagnetic or electronic decouplers with a constant deceleration setting are required. This type of disconnectors is used to perform time selectivity and limit the thermal impact of short-circuit currents on the electrical installation and device. The use of devices with "pseudo-time" selectivity ensures the selectivity of the operation of automatic switches in the area of short-circuit currents. Selectivity "SELLIM" is provided with a speed of 0.01 s, but it is possible only in automatic circuit breakers "Schneider Electric". Logical selectivity requires a communication channel between switching devices and the presence of circuit breakers with appropriate communication ports. It is easiest to ensure selectivity by using switches from the same manufacturer using selectivity tables. But such a solution is not always found in practice. The method of energy selectivity allows, taking into account the ratio between ratings, to implement either partial selectivity or full selectivity up to the limit of the breaking capacity of automatic switches. To ensure energy selectivity between two or more current-limiting devices, it must be taken into account that depending on the location of the short circuit, a different number of circuit breakers will be involved in limiting the emergency current, and therefore, the value of the limited current will also be different. By using circuit breakers with a high level of current limitation and a tripping speed that is inversely related to the short-circuit current, full selectivity can be provided at several levels of the network. This makes it possible to simplify the analysis of selectivity, minimize electrodynamic and thermal effects and reduce the level of voltage drop due to the action of a short circuit. Improvement of electrical installation protection systems makes it possible to design power supply systems without excessive reserves of electrical equipment overload, which reduces their cost, dimensions and weight. On the other hand, in the event of malfunctions in the operation of electrical equipment, this limits emergency currents and prevents failure of the undamaged part of the electrical installation, which significantly reduces downtime. Key words: selectivity, relay protection devices, circuit breakers, electrical devices, 0.4 kV network.

Numerical analysis on the failure characteristics of hot dry rock subjected to axial-torsional coupled percussion with single cutter

High-hardness and poor-drillability of hot dry rock (HDR) impose great challenges on drilling-rate improvement, limiting the economic exploitation of HDR geothermal. Axial-torsional coupled percussive drilling (ATCPD), as a potential drilling-rate improvement method, might provide solutions for achieving efficient breaking of HDR. To determine the rock breaking performance of ATCPD in HDR, we investigate the failure behaviors of high temperature rocks under percussion loads. Three loading modes, i.e., static loading, axial percussion loading, and torsional percussion loading, are compared with axial-torsional coupled percussion loading (A-TCPL) mode, with respect to rock breaking capacity and failure behaviors. The effect of some important engineering parameters, e.g., rock temperature, impact amplitude and frequency, is put particular emphasis to obtain the great rock breaking performance. Results show that ATCPD is characterized by the higher amplitude force, lower torque and larger cracking volume as compared to other loading modes, thereby resulting in a growth drilling efficiency. A-TCPD shows greater performance to high temperature rocks in stress response and material damage. The maximum principal stress, tensile and compressive damage factors are positively correlated with rock temperatures under A-TCPL mode. Increasing the impact amplitude and frequency are beneficial for inducing damage on rocks with temperatures ranging from 200 to 600 °C. By using the rock breaking total displacement as the evaluation index, the optimal ratio of axial to torsional impact frequencies for greater rock breaking capacity is obtained. For rocks at 200 °C, 400 °C, and 600 °C, the optimal ratio of axial to torsional impact frequencies is 1:2, 1:3, and 2:3, respectively. The results are expected to provide new insights to enhance drilling rate for geothermal well and HDR excavation.

Research on the influence of grain size of CuCr contact on the characteristics of cathode spot and cathode surface erosion in vacuum arc

CuCr alloy is widely used in vacuum interrupters. The characteristics of cathode spot and erosion of cathode surface directly affects the lifetime and breaking capacity of vacuum interrupter. In order to control the cathode spot and crater, two types of contacts with different Cr phase size were used in this paper. The vacuum arc breaking experiments were conducted. The cathode spot images were recorded by ultra high speed camera and craters were measured by Scanning Electron Microscope and Profiler. It was found that the smaller the Cr phase size, the higher the expansion velocity of cathode spots, the larger the number of cathode spot, the smaller the cathode spot size and the lower the current carried by each cathode spot. The reduction of Cr phase size helps to improve the uniform distribution of cathode spots on the contact surface. Besides, the smaller Cr phase size leads to the decrease of radius and depth of crater. For CuCr contacts, thermal diffusion process was analyzed and there is a significant difference in the thermal diffusivity between Cu and Cr. The Cr phase uniformly distributed in Cu prevents the thermal diffusion process which reduces the size of crater and the erosion of cathode surface.

Enhancement of Ru on furoic acid synthesis from furfural oxidation over Rux/δ-MnO2 catalysts

δ-MnO2 exhibits excellent activity for furfural oxidation to furoic acid under base-free conditions. However, its poor CH bond breaking capacity leads to lower conversion efficiency per unit mass catalyst than noble metal. Thus, a series of Ru-modified δ-MnO2 (Rux/δ-MnO2) have been made to enhance its CH bond breaking ability. The result showed that the furfural conversion was greatly enhanced on Rux/δ-MnO2 due to the enhanced capability for breaking the CH bond. Especially for Ru0.25/δ-MnO2, whose conversion rate per unit mass was 18 times higher than δ-MnO2. The characterization results showed that the Ru species mainly existed as single atoms or clusters on Ru0.25/δ-MnO2 and Ru0.5/δ-MnO2, while started to aggregate to RuO2 nanoparticles on Ru1/δ-MnO2 and Ru2/δ-MnO2. With the increase of Ru particles, the Ru's average oxidation state (AOS) decreased from +6 on Ru0.25/δ-MnO2 to +4.74 on Ru2/δ-MnO2. The Ru's TOF (intrinsic activity per Ru) was positively linearly related to the Ru's AOS. The electron-deficient Ru in Ru0.25/δ-MnO2 can strongly adsorb the H atom of the CH of geminal diol intermediate and accelerate the breakage of its CH bond. As a result, Ru in the Ru0.25/δ-MnO2 exhibited the highest TOF, which can even reach 29.85 mmolFF/mmolRu/h.

Structural design and flow field characteristics analysis of a new spin-on multi-hole jet drill bit for radial horizontal wells

In order to improve the rock breaking and drilling capacity of the jet bit in radial drilling, a new spin-type multi-hole jet bit was designed. The RNG K-ε turbulence model is used to analyze the flow characteristics of the internal and external flow fields of the designed jet bit, and the influence of the rotational speed and nozzle distribution on the flow field characteristics of the jet bit is analyzed to provide a basis for the design and structural parameter optimisation of the jet bit in radial horizontal wells. The results show that the internal flow field of the jet bit can be divided into four zones: the forward jet zone, the bottomhole overflow zone, the reverse overflow zone and the low-speed reverse flow zone. The reverse jet consists of six straight jets uniformly distributed along the circumferential direction and arranged at equal angles around the axis of the rotating body in the flow field. The reverse jet also impinges on the well wall to form an overflow zone, which provides self-propulsion and acts as a reaming agent. As the injection distance increases, the axial velocity rapidly decreases to zero and the decay velocity of the three groups of jets gradually approaches at the impact wall. Rotational speed has an effect on the decay of the flow velocity at the centre of the forward jet axis. When the angle of inclination is very small, the rotational speed has almost no effect on the decay of the axial velocity of the jet. The greater the angle of inclination, the greater the linear angular velocity at the jet exit, the more the jet mixes with the surrounding crossflow, the faster the dissipation of jet energy and the faster the jet decays along the axis. Controlling the magnitude of the rotational speed has to be taken into account in the design. Initially, the optimum values of the different structural parameters were determined as the central nozzle coinciding with the drill axis, the central forward nozzle deflection angle of 20°, the external nozzle deflection angle of 20° and the external nozzle tension angle of 15°.

The motion and distribution characteristics of cathode spot and its influence on plasma parameters

Cathode spots and plasma are the key factors affecting the breaking capacity of vacuum switches. In order to analyze the motion and distribution characteristics of cathode spot and its influence on plasmas, the experiments of cathode spot observation and plasma diagnosis were conducted in this paper. The cathode spot images were captured by ultra high-speed camera. Based on the continuous spectrum theory, the electron density was measured by the colorimetric thermometry. According to the cathode spot images and method of cathode spot recognition, the parameters of cathode spots including number, size and current were obtained. The changes of these parameters with arcing time and current amplitude were analyzed. The dependence of the cathode spots average size on spot current and spot expansion velocity was discussed. The axial and radial distributions of electron density were obtained which is related to the cathode spot distribution on the cathode surface. The significant fluctuation in the radial direction for electron density was observed.

KTX-이음 철도차량용 진공인터럽터 축자계 전극의 설계 및 검증

The main circuit breaker(MCB) used in railway vehicles has mainly applied a vacuum interrupter(VI) due to its long life and easy maintenance requirements. When an accident such as a short circuit or ground fault occurs in a railway vehicle, the VI may interrupt the fault current. The electrodes of the VI are closely related to the breaking performance, so it is very important to design the shape of them. In particular, when a high breaking capacity is required, such as railway vehicles, most manufacturers control the arc by applying a axial magnetic field electrode in VIs. For a axial magnetic field electrode, by diffusing the arc throughout the electrode surface by a magnetic field, melting of the contact can be minimized and the electrical endurance life can be improved. The breaking performance of VIs could be verified through a high power short-circuit test, but it takes a lot of cost and time, so most manufacturers evaluate the breaking performance through magnetic field analysis, but the validity of analysis result is not verified. In this study, an electrode of a vacuum interrupter applied to a high-speed vehicle was designed, and a magnetic field analysis was performed to verify its effectiveness, and a sample was manufactured for an actual electrode part to measure magnetic flux density. As a result of comparing the analysis and the measured values, similar results were confirmed in most parts except for the center and edge of the electrode, and the validity of the design was verified.

Study of Arc Interruption Characteristics under Rated Current in Low Voltage Circuit Breakers

The breaking capacity of rated current is one of the important indexes to evaluate the performance of circuit breakers, which is usually measured experimentally and cannot be analyzed in terms of the arcing characteristics of the opening process. Simulation methods based on the magnetohydrodynamic (MHD) model of the arc can be used to obtain the macroscopic motion of the arc within the interrupter and the interaction of the arc with the contacts, walls, and splitter plates. Therefore, this paper focuses on the arc interruption characteristics’ underrated current in low voltage circuit breakers by MHD simulation. A more accurate and effective field-circuit coupling MHD simulation model of low voltage circuit breaker products is developed in this paper. A nonlinear conductivity model of the sheath layer is considered to better simulate the near-pole voltage drop and bending processes after the arc has been cut by the splitter. The time-dependent magnetic field generated by the arc is considered in the calculation. Additionally, the real-time parameters of the external circuit are coupled to reflect the evolution of the arc characteristics under the action of the external circuit. The simulation results intuitively and clearly show the evolution of the arc during the breaking process. Through this, an arc extinguishing chamber can be designed to effectively regulate the arc interruption characteristics, thereby improving the breaking capacity of the circuit breaker. The accuracy and efficiency of the proposed simulation method is verified by experiments. This method can be extended to the performance analysis of AC/DC low voltage circuit breakers.

Results of Experimental and Theoretical Studies of the Possibilities of the Resonance Method of Ice Cover Destruction

Based on experiments carried out: in ice basins; with large-scale models of hovercraft in the field; with full-scale hovercraft, as well as using theoretical dependencies for calculating the stressstrain state of the ice cover from the action of moving loads, the possibilities (patterns) of the resonant method of ice destruction, i.e., by excitation of resonant flexural-gravity waves (FGW), were studied. Its physical essence, the expediency of its implementation by a hovercraft are explained, the possible areas of effective use of this method are indicated. The results of the information review on the topic of the work are given, on the basis of which the purpose of the research is set. When describing the viscoelastic nature of the relationship between stresses and strains in ice, the Kelvin-Voigt law of deformation of an elastically retarded medium was used. The theoretical bending potential energy density of an infinite plate was taken as a criterion for the ice breaking capacity of FGW. In this case, the condition is used that when it reaches a certain value, complete (with the opening of cracks) destruction of ice occurs. The initial data for these calculations are taken from the performed experiments. Dependences are given that make it possible to determine the parameters of a load moving at a resonant speed (hovercraft parameters) sufficient to destroy an ice cover of a given thickness under given ice conditions.