Numerical analysis of switching performance evaluators in low-voltage switching devices

An arc modelling is a valuable and useful tool to evaluate the switching performance of low-voltage switching devices (LVSDs) during breaking operation before testing real products. Moreover, it helps improve interruption capability of LVSDs and optimize them. This paper focuses on the numerical simulation of the arc behavior in AC devices before zero current and prediction of the re-ignition after current zero based on the simulated arc voltage. The 3-D arc modelling is based on the conventional magnetohydrodynamics theory and it considers the motion of a contact, arc root, radiation and air properties which vary with the temperature and pressure

ARC MOTION IN LOW VOLTAGE CIRCUITBREAKER (LVCB) EXPERIMENTAL ANDTHEORETICAL APPROACHES

International audienceAbstract This paper is related to the study of the arc motion in simple low voltage circuit breaker geometry.Experimental and theoretical approaches are investigated respectively by fast camera and by a magneto hydrodynamicmodel. Two theoretical methods have been developed to characterize the arc movement called MECM (Mean ElectricalConductivity Method) and GCRM (Global Current Resolution Method). The results obtained by the two models are ingood agreement with the experimental observations. The MECM allows obtaining faster results but the stagnation phasesare well represented with the GRCM and this last method is easier to implement in more complex geometry. The resultsshow also the importance of the exhaust description on the arc behavior

Modelling and Simulation of SF6 High-Voltage Circuit-Breakers - an Overview on Basics and Application of CFD Arc Simulation Tools

The paper gives an overview on the basics of CFD arc simulation tools with respect to the simulation of the fluid mechanical processes in the interrupter unit of SF6 high-voltage circuit-breakers at no-load and short-circuit switching-off processes. On the example of SF6 self-blast circuit-breakers the complete process from the analysis of the switching-off process to the creation of a modular simulation model consisting of several sub models is illustrated. Details to the modelling in the particular sub modules and to the implementation are given. The capability of a CFD arc simulation tool based on the program package ANSYS/FLUENT is demonstrated on the basis of selected simulation results. Furthermore case examples for the application of the presented CFD arc simulation tool in the development process of high-voltage circuit-breakers are given

Environmental Compatible Circuit Breaker Technologies

Recent research and development in the field of high-current circuit breaker technology are devoted to meeting two challenges: the environmental compatibility and new demands on electrical grids caused by the increasing use of renewable energies. Electric arcs in gases or a vacuum are the key component in the technology at present and will play a key role also in future concepts, e.g., for hybrid and fast switching required for high-voltage direct-current (HVDC) transmission systems. In addition, the replacement of the environmentally harmful SF6 in gas breakers and gas-insulated switchgear is an actual issue. This Special Issue comprises eight peer-reviewed papers, which address recent studies of switching arcs and electrical insulation at high and medium voltage. Three papers consider issues of the replacement of the environmentally harmful SF6 by CO2 in high-voltage gas circuit breakers. One paper deals with fast switching in air with relevance for hybrid fault current limiters and hybrid HVDC interrupters. The other four papers illustrate actual research on vacuum current breakers as an additional option for environmentally compatible switchgear; fundamental studies of the vacuum arc ignition, as well as concepts for the use of vacuum arcs for DC interruption

Modelization and analysis of the electric arc in low voltage circuit breakers

246 p.Tesis doctoral que presenta un nuevo modelo de arco eléctrico para interruptores de baja tensión mediante simulación FV y validación experimental

Arc Modeling in Industrial Applications

Simulation methods are routinely applied in the design and development process of power distribution devices. Arcing phenomena that occur during switching operations or fault events are modeled to optimize device performance and gain deeper insights into the behavior that testing cannot easily provide. In this contribution, some applications are presented in detail. The first example describes the distribution of debris that is generated inside a molded case circuit breaker (MCCB) during short-circuit interruption. A model is used to analyze the debris transport and to derive a solution to address issues caused by the debris. Second application example is a cooling device for hot plasma gases vented by circuit breakers. A model driven design process helps to define the device dimensions to achieve a safe temperature level of the exhaust gases. The third example deals with short-circuit behavior of a hollow core high voltage surge arrester, comparing model and experimental results

Modelling of High Voltage Circuit Breakers Considering Interaction between the Driving Mechanisms and Switching Arcs

With the increase of voltage and current ratings, design and test of circuit breakers have become more demanding. This is a consequence of the technical difficulties and costs in performing development tests as well as the complexity resulting from the coupling of different physical mechanisms in shaping the interruption performance of a breaker. It is well known that the performance of a circuit breaker is determined by many design and operational parameters among which the motion characteristic of the contact is a key factor. Since the motion characteristic of the contacts has a direct impact on breaker performance, it plays a critical role in the design of a circuit breaker. Difficulties in performing tests or experiments under high voltage and power have rendered the traditional ‘cut and try’ design approach impractical. Computer simulation on the other hand, with its cost-effective and easy-to-implement nature, has become the favored approach to achieve design optimization and attracted a great amount of attention in the field of electrical engineering. An arc simulation model (Liverpool arc model) has been developed in this research group together with a circuit breaker simulation interface, featuring PHEONICS as the differential equation solver. Valuable information can be extracted from arc simulation results and help design better optimized prototypes. However, the absence of a driving mechanism model in the current arc simulation model limits its effectiveness and functionality. The travel of the contact could affect the flow cross section in the arc chamber as well as the length of the arc, and ultimately the performance of the circuit breaker. Additionally, the interaction between the arc chamber and driving mechanism, which has a significant impact on the result (most prominent under high current and long arc duration), has also been overlooked in the existing model. Previously, the absence of a driving mechanism model is dealt with by providing the simulation with a user-defined text file containing the travel profile of the moving contact. However, a user defined file may not reflect the true motion of the moving contact due to the unaccounted interaction between the arc chamber and driving mechanism. Consequently, a truly coupled simulation model, which is capable of calculating the travel of all moving components in real time and eliminating any inaccuracies in the predefined travel curves, is needed. In the current research, an approach to quantify the interaction between the arc and driving mechanism has been proposed. Collectively, the resistive force (known as reaction force) imposed on the moving components in the arc chamber by the high-pressure gas can be calculated by a newly developed integral method. The existing arc model has been expanded to incorporate the calculation of reaction force. In addition, a functional mathematical model for the ZF-11-252 (L)/CYTA hydraulic driving mechanism has also been developed, based on which a number of sensitivity studies have been carried out and the key design parameters that affect the dynamic characteristics of the driving mechanism identified. Considering both the driving mechanism model and the improved arc model (which can now calculate reaction force based on the pressure distribution in the arc chamber) a coupled circuit breaker simulation procedure has been established together with an interface which facilitates the information exchange between the driving mechanism model and the arc model. Based on this coupled model, the interaction between the arc and the driving mechanism is studied under different arcing conditions and nozzle geometries. In particular, two important factors affecting the accuracy of the predicted travel characteristics of the moving components have been identified through the studies. The first one is the need to consider the variable contact surface area between the piston rod in the hydraulic cylinder and the oil as a result of the motion of the piston. The second factor is the prediction accuracy of the pressure field around the moving components in the arcing chamber, especially when there are strong pressure waves propagating in the arcing gas. These aspects have not been studied so far

Fluid Dynamics Calculation in SF6 Circuit Breaker during Breaking as a Prerequisite for the Digital Twin Creation

The requirements to switching the capacities of SF6 circuit breakers submitted by Russian Grid companies are difficult to satisfy. The first limitation is related to material and financial costs in order to create a new requirement-satisfying switching device. The second limitation is dictated by the necessity of calculating complex physical processes in a circuit braker interrupter during fault–current making or breaking before creating a prototype. The latter task is reduced to the problem of simulating the processes of interaction between the switching arc and the SF6 gas flow. This paper deals with the solution of the problem both analytically by a special method and numerically by a numerical software package through the creation of a mathematical model of the interaction process. The switching arc is taken into account as a form of a temperature source, based on experimental data on measuring the temperature of the arc column. The key feature of the research is to use the finite element method based on a moving mesh—the Arbitrary Lagrangian Eulerian (ALE) method. Such a problem statement allows us to take the contact separation curve of the circuit breaker into account as the input data of the model. The calculations were carried out during fault-current breaking by a 110 kV SF6 dead-tank circuit breaker. The calculations of pressure and mass flow in the under-piston volume change, gas flow speed, and temperature depending on the contact separation are given. The proposed model of the switching arc was used to simulate the process of 25 kA symmetrical fault–current breaking and was compared with an experiment. © 2023 by the authors.Ministry of Education and Science of the Russian Federation, Minobrnauka: FEUZ-2022-0030The research was carried out within the state assignment with the financial support of the Ministry of Science and Higher Education of the Russian Federation (subject No. FEUZ-2022-0030 Development of an intelligent multi-agent system for modeling deeply integrated technological systems in the power industry)

Computer simulation of fundamental processes in high voltage circuit breakers based on an automated modelling platform

Auto-expansion circuit breakers utilize the arc’s energy to generate the flow conditions required for current interruption. The operation of this type of circuit breaker is extremely complex and its interruption capability depends on the whole arcing history as well as a number of geometric factors. On the other hand, circuit breaker development based on test is extremely expensive and time consuming. The accumulated understanding of the underlying physical processes so far enables arc models be used as a tool for optimum design of switchgear product such as high voltage circuit breakers. For academic research, there is often a need to study the performance of a newly developed arc model by inspecting the distribution of relevant physical quantities during a simulation and their sensitivity to model parameters in an efficient and convenient approach. However the effective use of computer simulation by design engineers has been hindered by the complexity encountered in model implementation. This thesis presents the development and structure of an automated simulation tool, the Integrated Simulation and Evaluation Environment (ISEE), for the arcing process in gas-blast circuit breakers. The functionalities of ISEE are identified and developed based on the experience in real product design, which include visual creation and definition of components, automatic setup of arc models based on a commercial CFD software package as equation solver, simulation task management, and visualization of computational results in “real-time” mode. This is the first automated simulation platform in the community of switching arc simulation. Using ISEE as the simulation tool, different designs of auto-expansion circuit breakers have been investigated to reveal the fundamental characteristics of the arcing process under different test duties. Before attempting to investigate the capability of an auto-expansion circuit breaker, the fundamental issue of determining the turbulence parameter of the Prandtl mixing length model is addressed. Previous studies on turbulence arcs were mostly concerned with simple converging-diverging nozzles. There has been little work on real circuit breaker nozzles. In order to calibrate the turbulence parameter, real arcing conditions including interrupting currents, contact travels, and transient recovery voltages of two commercial circuit breakers, with rated voltage of 145 kV and 245 kV, have been used together with the geometry of the circuit breakers to calibrate the range of the turbulence parameter. The effect of nozzle ablation has been considered. All together 6 cases have been used for three circuit breakers with each pair of cases corresponding to a success and failure in its thermal recovery process. It has been found that a single parameter of 0.35 is applicable to all three circuit breakers with an auxiliary nozzle and a main nozzle of converge-flat throat-diverge shape. It must be noted that this value is obtained with the definition of thermal radius introduced in Chapter 3 and the assumption that the parameter linearly changes with the interrupting current from 0.05 at 15 kA to 0.35 at current zero. Using the calibrated turbulence model, a computational study of the thermal interruption performance of a 145 kV, 60 Hz auto-expansion circuit breaker with different arc durations has been carried out in Chapter 4. The relation between pressure peak and current peak in the auto-expansion circuit breaker is discussed. It has been found that a larger average mass flux in the main nozzle indicates a better interruption environment, enabling the circuit breaker to withstand a larger rate of rise of recovery voltage after current zero. Another important finding is that the auxiliary nozzle plays an important role in an auto-expansion circuit breaker both at the high current phase and during the current zero period. Therefore, the proper design and use of an auxiliary nozzle is a key factor to enhance the thermal interruption capability of high voltage auto-expansion circuit breakers. In Chapter 5 of the thesis, the transient pressure variation in auto-expansion circuit breakers was studied. The pressure variation has an extremely complex pattern and the pressure changes in different ways depending on the location in the arcing chamber. It is shown, for the first time, that the time lag between the current peak and pressure peak in the expansion volume can be explained by using an energy flow rate balance method, that is flow reversal occurs when the enthalpy exhaustion rate from the contact space equals the electrical power input. Following the flow reversal, a high enthalpy flow rate from the expansion volume into the contact gap first occurs for a short while (1 ms), which is followed by a high mass flow rate of relatively cool gas at less than 2000 K. This high mass flow rate causes a surplus in mass flow rate into the contact gap and results in the last temporary pressure peak in the contact space before the pressure and flow field finally settle down for arc quenching at current zero. The pressure change under different conditions, i.e. different arc durations, different current levels and different length of the heating channel, has also been studied in details. In summary the present research leads to original findings in three aspects of the operation of auto-expansion circuit breakers, i.e. the calibration of the turbulence parameter for the Prandtl mixing length model, interruption performance with different arc durations, and the transient pressure variation in the arcing process. The results are expected to provide useful information for the optimum design of auto-expansion circuit breakers