Breaking Capability Research Articles

DC circuit breaker: A topology with regenerative current breaking capability for DC microgrid applications

The modern DC grid is predominantly inductive due to several factors, including line inductance, and the use of current-limiting inductors to control fault current rising rates. These network inductances store a significant amount of energy during regular operation, which is either dissipated or freewheeled to ensure safe current breaking. This research article proposed a highly efficient bidirectional DC circuit breaker topology that not only provides safe current breaking but also effectively recovers the post-current breaking energy from the network’s inductance instead of dissipation. An extensive simulation investigation is performed in PSIM software to test the breaker capability for a 400V/400A DC system and the laboratory-scale 48V/1A experimental setup has been developed and employed for further validation purposes.

Effects of shell mold heating temperature on microstructures and freckle formation of single crystal superalloys

To study the effects of shell mold heating temperature on the microstructure and freckle formation of single crystal superalloys, the directional solidification experiment and simulation were conducted with designed stepwise specimens. The temperature field and morphology of mushy zone were analyzed. The results show that the primary and secondary dendrite arm spacings both decrease with the rise of shell mold heating temperature. This reduces the permeability of the liquid in the mushy zone and the width of the thermal-solutal convection channel, which reduces the formation tendency of freckles, the width of freckles and the number of dendritic fragments in freckled areas. In addition, with the increase of shell mold heating temperature, the cooling rate of liquid in the mushy zone increases, which reduces the cooling time of the melt in the mushy zone, weakens the breaking capability of liquid flow to the dendrite, and further reduces the tendency of freckle formation in single crystal superalloy castings.

Research of simulation and experiment on arc characteristics of gas mechanical switch

AbstractAn arc is the high‐temperature discharge plasma produced in the opening process of mechanical switches, which directly affects the breaking capability of a hybrid DC circuit breaker. According to the physical mechanism of an electric arc, the construction of an arc model for simulation analysis is an important technical means in the electrical field. In this study, based on the theory of magneto hydrodynamics (MHD), a gas mechanical switch model of a natural commutation DC circuit breaker with a compound gap is established. The arc motion process under different conditions is simulated and calculated. The influence of different initial pressures, different opening speeds, and different striking currents on the arc voltage characteristics is analysed. The results show that the larger the gas pressure, the smaller the arc volume and the higher the arc voltage. The faster the opening speed, the longer the arc and the higher the arc voltage; with the increase of the current, the arc voltage increases rapidly at a low current, while the arc voltage increases slowly at a high current.

Influence of Ultra-High-Voltage hybrid reactive power compensation on interruption performance of circuit breakers under different faults

For extremely large ultra-high-voltage (UHV) power transmission and distribution lines with typical project using hybrid reactive power compensation (HRPC), single-phase earth fault (1LG), three-phase ground fault (3LG), phase-to-phase fault (2LS), and two-phase grounding fault (2LG) often occurs. Circuit breaker is one of the most critical equipment of UHV transmission system. And the interruption performance is crucial to circuit breakers’ breaking capability. In this study, formal expressions of the indicators for the interruption performance of the circuit breaker are deduced in case of different faults based on the equivalent-valued parameter circuit based on the structure a UHV demonstration project. The simulations are used to validate the accuracy of formal expressions. Then, the influence of such factors as the location of the fault and the degree of HRPC on the interruption performance of the 1LG, 2LG, 3LG, and 2LS is analyzed. Finally, the interruption performance of circuit breakers under different faults are compared. A quantitative evaluation of the influence of changes in the relevant indicators on the interruption performance of circuit breakers can provide a technical basis for choosing the appropriate design of the circuit breaker in light of the application as well as equipment development and assessment.© 2017 Elsevier Inc. All rights reserved.

Numerical investigation of ice plate fractures upon rigid ball impact

The fracture process and breaking capability of ice cover impacted by high-speed projectiles before underwater explosion is an urgent subject of scientific research in ice engineering applications. This paper presents the results of numerical simulations of the dynamic fracture behaviour induced by the impact of a small spherical projectile on an ice plate. The proposed 3D rate-dependent peridynamics model is validated by the dynamic ring Brazilian disc testing of ice specimens. Good agreements between the present model and the previous experiments are obtained in ice breaking processes and damage patterns of thin, medium and thick ice plates. Several cases are analysed and discussed in terms of various impact velocities, ice thicknesses, and boundary constraint conditions. The simulations identify detailed fracturing characteristics that are not observed in experiments, including the sequence and shape of crack propagation in a short time interval, the crater formation and the damage evolution along the thickness direction. The proposed peridynamics computational model provides new understanding of the potential of using penetrator–ice block impact tests to observe the evolution of complex brittle damage and reveal the failure mechanism.

Control Strategy of Suppressing Short-circuit Current VSCs Feeding into the AC Grid in a Hybrid Cascaded UHVDC System

Hybrid cascaded ultra-high voltage dc is a new dc technique with a line commutated converter cascaded with one or several voltage source converters. It is an effective solution for large capability transmission as well as improving the stability of the ac grid with multiple dc transmission systems feeding in. Baihetan-jiangsu dc project in China is the first cascaded ultra-high voltage dc project in the world. For a receiving end with a strong ac system, the short circuit current is always large and close to the maximum ac breaker breaking capability, which is a threat to the ac system fault clearance. In this paper, the issue of excessive short circuit current in a hybrid cascaded ultra-high voltage dc system is discussed and revealed. The process of the short circuit current developing is divided into 2 stages. Characteristics and the calculation method of the short circuit are proposed, and based on this, a control method is proposed, which can suppress the short circuit current during the fault clearance effectively. The parameter setting method is proposed. Finally, based on the scenario of the Baihetan-jiangsu dc project, the strategy and the parameters setting method are validated under PSCAD/EMTDC.

Reduction of the DC Circuit Breaker Requirements by Bidirectional Solid-State Fault Current Limiter in DC Grid

Reliable and economic protection of DC grids against fault currents is the main challenge for the development of voltage source converter-based DC grids. Application of fault current limiters (FCLs) can limit the rapid increase of fault current and reduce the DC circuit breaker (DCCB) requirements to isolate the fault. This article reports a bidirectional solid-state FCL (BSSFCL) to protect the DC lines against DC short circuit fault. In addition, it can limit fault current in both directions. The circuit and principle operating of the proposed BSSFCL are presented. Then, the current limiting performance of the proposed BSSFCL is analyzed and its parameter design requirements are presented. Finally, the performance of the proposed BSFFCL is compared with that of the RL-current limiting circuit (RL-CLC), mutual inductance-type FCL (MIFCL), and restive mutual-inductance solid-state FCL (RMI-SSFCL). The numerical analysis and simulations were done using the PSCAD/EMTDC software. It was found that, the BSSFCL could effectively enhance the breaking capability of DCCBs. Moreover, it outperforms the RL-CLC, MIFCL, RMI-SSFCL in terms of the fault current limiting, the fault clearing time and metal oxide arrester (MOA) energy absorption of DCCBs.

Thermosensitive Biomimetic Hybrid Membrane Camouflaged Hollow Gold Nanoparticles for NIR-Responsive Mild-Hyperthermia Chemo-/Photothermal Combined Tumor Therapy.

As an appealing biomimetic strategy for various medical applications, cell membrane coating lacks sensitive on-demand breaking capability. Herein, we incorporated thermosensitive lipid (TSL) membrane into red blood cell (RBC) and MCF-7 cancer cell (MC) hybrid membrane ([RBC-MC]M) vesicles. The [RBC-MC-TSL]M was coated onto doxorubicin (Dox)-loaded hollow gold nanoparticles to enhance chemo-/photothermal combined tumor therapy at a mild hyperthermia temperature (≤49 °C). Double-layer coating with TSL and [RBC-MC-TSL]M as the inner and outer layer, respectively, presented better antileakage and higher NIR-responsivity than single-layer coating. The Dox release ratio upon NIR laser irradiation (≤49 °C) was 74.6%, much higher than that (33.5%) without NIR laser. The nanodrug can be efficiently and specifically taken up by MCF-7 cells. In addition, the nanodrug exhibited excellent tumor-targeting property, with 4.08- and 1.12-times Dox accumulation in MCF-7 tumors compared to free Dox and [RBC-MC]M-coated counterpart, respectively. Most importantly, TSL incorporation significantly enhanced NIR-responsive antitumor efficiency, with tumor growth inhibition ratio increased from 35.1% to 48.6% after a single dose administration. Besides, the nanodrug exhibited very good biocompatibility. Camouflaging nanoparticles with the thermosensitive biomimetic hybrid membrane provides a painless and promisingly clinical-applicable approach for effective chemo-/photothermal combined mild-hyperthermia tumor therapy.

12-kV 1-kA Breaking Capable Modular Power Electronic Interrupter With Staged Turn-off Strategy for Medium-Voltage DC Hybrid Circuit Breaker

The dc circuit breaker plays an important protection role in the dc distribution systems. Hybrid dc circuit breaker (HCB) offers low conduction losses and reasonably fast response times. In this article, a high power density, modular, and scalable power electronic interrupter (PEI) design is introduced for medium-voltage (MV) HCB platforms. Following this concept, the single low-voltage module is first investigated in terms of the high pulse current ratio and the voltage clamping circuit. After the comparison and test among different devices, a compact module with 1.7-kV discrete IGBTs are selected as main switches. While the voltage clamping circuit is carefully designed to guarantee no tail current bump and sufficient turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> voltage margin. Next the whole system with series modules is optimized on the aspects of the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> strategy, power supply structure, and layout of modules. An improved staged turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> scheme is proposed, which can not only reduce the peak current and total metal oxide varistor (MOV) energy, but also help balance the MOV energy distribution. A 12-kV and 1-kV breaking capable PEI was demonstrated based on the proposed PEI design, achieving a peak power density of 7.4 kW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , much higher than the IGBT module-based solution. The breaking capability and effectiveness of the modular PEI is demonstrated in a 6-kV MVDC HCB device.

On the geometry of symmetry breaking inequalities

Breaking symmetries is a popular way of speeding up the branch-and-bound method for symmetric integer programs. We study fundamental domains, which are minimal and closed symmetry breaking polyhedra. Our long-term goal is to understand the relationship between the complexity of such polyhedra and their symmetry breaking capability. Borrowing ideas from geometric group theory, we provide structural properties that relate the action of the group with the geometry of the facets of fundamental domains. Inspired by these insights, we provide a new generalized construction for fundamental domains, which we call generalized Dirichlet domain. Our construction is recursive and exploits the coset decomposition of the subgroups that fix given vectors in $${\mathbb {R}}^n$$ . We use this construction to analyze a recently introduced set of symmetry breaking inequalities by Salvagnin (Symmetry Breaking Inequalities from the Schreier-Sims table. In: International Conference on the Integration of Constraint Programming, Artificial Intelligence, and Operations Research, pp. 521–529, 2018) and Liberti and Ostrowski (J Global Opt 60:183–194, 2014), called Schreier-Sims inequalities. In particular, this shows that every permutation group admits a fundamental domain with less than n facets. We also show that this bound is tight. Finally, we prove that the fundamental domain defined by the Schreier-Sims inequalities can contain an exponential number of isomorphic binary vectors for a given permutation group G. This provides evidence of the lack of symmetry breaking effectiveness of this fundamental domain. Conversely, a suitably constructed GDD for this G has linearly many inequalities and contains unique representatives for isomorphic binary vectors.

Multimode polariton effects on molecular energy transport and spectral fluctuations

Despite the potential paradigm breaking capability of microcavities to control chemical processes, the extent to which photonic devices change properties of molecular materials is still unclear, in part due to challenges in modeling hybrid light-matter excitations delocalized over many length scales. We overcome these challenges for a photonic wire under strong coupling with a molecular ensemble. Our simulations provide a detailed picture of the effect of photonic wires on spectral and transport properties of a disordered molecular material. We find stronger changes to the probed molecular observables when the cavity is redshifted relative to the molecules and energetic disorder is weak. These trends are expected to hold also in higher-dimensional cavities, but are not captured with theories that only include a single cavity-mode. Therefore, our results raise important issues for future experiments and model building focused on unraveling new ways to manipulate chemistry with optical cavities.

A Novel Thyristor-Based Bidirectional SSCB With Controllable Current Breaking Capability

In view of low conduction loss and low cost, thyristors are good candidates for configuring solid-state circuit breakers (SSCBs). However, due to the half-controlled characteristic of thyristors, it is difficult for the thyristor-based SSCBs (TCBs) to achieve a fully controllable current breaking capability. In this article, a novel bidirectional TCB is proposed, which can fully control the current breaking process with simple structure and control strategy. Besides, the proposed TCB can break current without creating current surges to the source and load, thereby enhancing the reliability of direct current systems. Typical advantages of high power efficiency and low cost can also be obtained from the novel topology. Operation process and circuit design of the proposed TCB are presented. The effectiveness of the proposed solution is verified by the experimental results.

A Novel DC Circuit Breaker With Counter-Current Injection and IGCT Combined

The fast fault clearance in medium voltage direct current (MVDC) grids requires the DC circuit breakers (DCCBs) with high breaking capability and low cost. The traditional hybrid DCCB realizes large current interruption relying on several insulated gate bipolar transistors (IGBTs) in parallel, which results in difficulty of cost reduction. In this paper, a novel DC circuit breaker with counter-current injection and integrated gate-commutated thyristor (IGCT) combined is proposed and analyzed. By combining forced commutation and IGCT, the large current breaking capability can be realized and the low cost is guaranteed. The simulation of the proposed DCCB is performed to evaluate the fault current breaking capability and influence of circuit parameters consisting of stray parameters and pre-charged capacitors on current commutation processes. Furthermore, a prototype of the 10 kV MVDC circuit breaker with 20 kA breaking capability is developed, then the fault current breaking test is carried out to verify the validity of the proposed topology which can cut off current within 2.5 ms. 1

Research on characteristics of 6-inch IGCT with 15kA turn-off capability in DC circuit breaker

The development of DC power grids requires DC circuit breaker(DCCB) to have higher breaking capacity. As a key component of DCCB, the withstand voltage and breaking capacity of power electronic devices affect the structure and cost of DCCB. Therefore, it is necessary to upgrade power electronic devices to improve the breaking capability of DCCB and reduce costs. Integrated gate commutated thyristor (IGCT) has great advantages in the application of DCCB due to its inherent high inrush current capacity and low on-state loss. This article introduces a novel IGCT used in DCCB. It is based on the existing 6-inch 4.5kV GCT chip and shell structure. After designing a new gate unit and optimizing the turn-off circuit, it effectively improves the turn-off capability of the device. In the DC circuit breaker application topology, the device has a turn-off capability of 15kA at 2400V. This new device is expected to further increase the breaking capability of DCCB in the future.

Review on key technologies of DC high speed switch in a multi-terminal UHVDC system

Multi-terminal HVDC (High Voltage Direct Current Transmission) technology is one of the effective technologies to solve the shortage of transmission corridors and connection issues of large-scale renewable energy grid in China. The function of a High Speed Switch (HSS) is to implement on-line switching and fault isolation of the third station in a multi-terminal HVDC system. However, 800kV HSS still relies on importation and 800kV HSS has become a “neck-jamming” equipment for the development of the multi-terminal HVDC transmission system. In order to obtain the core technologies, this paper first briefly introduces the roles of a HSS played in a multi-terminal hybrid HVDC project, and summaries the operating conditions and key technical parameters. Secondly, this paper focuses on the long-term arcing tolerance ability and DC breaking capability without oscillation circuits required by a 800kV HSS. Further, its research and development status are investigated. Finally, suggestions for the future research directions are given for 800kV HSS localization.

Effect of EDMed rake face grooves on the chip breaking capability of twist drills during deep hole drilling of Al 6061 aluminum alloy

ABSTRACT Deep hole drilling of ductile materials like Al6061 with conventional twist drills is challenging due to premature tool failure caused by chip clogging. Chip breakers, in the form of grooves of varying angles (0°, 5° & 10°) and depth (0.4 & 0.5 mm), created using EDM on the rake face, are proposed to overcome chip clogging. Tool wear, hole roughness, and diameter deviation were measured and analyzed along with chip morphology study for the six grooved tools and compared with plain drill. The grooved tools were successful in breaking the chips which allows for easy evacuation without any clogging. Grooved drills produced desired spiral chips compared to string chips produced by plain drill thus resulting in lesser tool wear rate. While the grooved tools showed stable but slightly higher roughness values, the conventional tools exhibited a linear increasing trend as the drilling progressed. The machined hole surfaces had defects such as feed marks, pitting, grooves, and burnished surfaces. The grooved tools produced comparatively more diameter deviation probably because the well broken chips entered into the drill land/hole surface space. From the results it is clear that groove angle and depth have significant effect on the drill machinability characteristics.

Simulation and Experimental Study on Characteristics of Multiorifice Nozzle in Radial Jet Drilling

The radial jet drilling (RJD) is a key technology to improve the development efficiency of low-permeability oil and gas resources. In order to seek a reasonable hydraulic engineering parameter combination of hydraulic radial jet drilling, to obtain the optimal hydraulic energy distribution, a jet radial horizontal drilling simulation experiment system of the casing windowing is designed. A sequence of experimental investigations focused on engineering parameters of pump displacement, rotating speed, and frequency of high-pressure plunger pump is performed, and the operability and the feasibility of the experiment are verified. To evaluate the maximum drillable length and the self-propelled force of a jet nozzle, a 3D numerical model based on ANSYS-CFX is developed to evaluate the effects of the inlet flow displacement, the flow rates ratio K , and the angle ratio F : B of the forward orifice and backward orifice of the jet nozzle on its maximum drillable length and self-propelled force by sensitivity analysis. Finally, the comparison of numerical simulation results (Ln), mathematical results (Lm), and experiment results (Le) of the maximum drillable length are presented. It is observed that the simulation results are consistent with the experiment results with an average accuracy of 97.07%. Therefore, the proposed numerical model has a good performance in predicting the maximum drillable length of the multiorifice nozzle. The research results can provide theoretical guidance for improving the rock breaking and drilling capability of radial jet drilling technology.

Protection of MTDC Network Using a Resistive Type Superconducting Fault Current Limiter

Multi-terminal DC network (MTDC) offers great potential for long distance huge power delivery with multi-direction power transmission capability. However, the key obstacle in a realization of MTDC is the lack of existing commercial protection device can withstand the DC fault that rises rapidly and surge tenfold within several milliseconds over the whole system. The new technology called Superconducting Fault Current Limiter (SFCL) could bring a solution to the main bottleneck of the MTDC networks. In this work, an electro-thermal model of resistive type SFCL in series with a hybrid DC circuit breaker is proposed to protect a five terminal MTDC network. The numerical analysis carried out using (EMTP-RV®) software, and the simulation results show how effectively the SFCL can reduce the fault current and increase the breaking capability. Moreover, system stability is remarkably improved.

A new direct current circuit breaker with current regeneration capability

Direct current (DC) power systems are becoming very popular due to better control ability and equipment reliability thanks to the continuous development of power electronics. A DC circuit breaker (DCCB) used for current interruption in a DC network is a major part of the system. It plays the vital role of isolating networks during fault clearing as well as during normal load switching. Breaking the DC current is a major challenge as it does not have any natural zero crossing points like the AC current has. In addition, energy stored in the network inductances during normal operation opposes the instantaneous current breaking. Hence, all the conventional DC circuit breaker topologies use lossy elements to dissipate this stored energy as heat during the current breaking operation. However, it is possible to store this energy and reuse it later by developing an improvised topology. In this paper, the prospects of energy recovery and reuse in DC circuit breakers have been studied, and a new topology with regenerative current breaking capability has been proposed. This new topology can feed the stored energy of the network back into the same network after breaking the current and thus can improve the overall system efficiency.

Combinatorial Multi-Objective Optimization of Resistive SFCL and DC Circuit Breaker in Hybrid HVDC Transmission System

To cope with the DC fault isolation issue of a hybrid high-voltage direct-current (HVDC) system, a promising option is to coordinate superconducting fault current limiter (SFCL) and DC circuit breaker (DCCB). In this paper, a multi-objective Pareto optimization method is proposed for the combinatorial use of a resistive-type SFCL and a DCCB in a hybrid HVDC. Firstly, theoretical modeling and coordinated action process of the SFCL and DCCB are expounded. Then, a multi-objective function that collaboratively minimizes the SFCL resistance and the breaking capability of the DCCB is established, and a non-dominated sorting genetic algorithm-II (NSGA-II) is utilized to acquire the satisfying Pareto optimal solution set. The optimizing calculation is done in a 320 kV hybrid HVDC for validating the approach efficacy. Besides, transient simulations are implemented by PSCAD/EMTDC, and comprehensive performance analyses are executed to evaluate the rationality of the combinatorial optimal schemes. The findings indicate that the DC fault current is reduced and interrupted with the minimal rating of the resistive-type SFCL and the DCCB, and also, the HVDC system's safe and stable operation will be ensured. Therefore, the proposed approach is adequately verified for its availability and feasibility.