Medium Voltage Vacuum Circuit Breakers Research Articles

Microstructure and arc erosion behavior of WC/CuCr30 composites based on nano-Cr precipitation

CuCr alloys with high contact performance for medium and high voltage vacuum circuit breakers are becoming increasingly urgent. In this work, WC/CuCr30 composites were prepared by SPS process, and nanometer-sized precipitated Cr phases were obtained by subsequent heat treatment. The microstructure and arc erosion behavior were investigated. The results show that nano-Cr phase precipitated in copper matrix can effectively improve the interfacial bonding strength between the Cu matrix and WC particles, and part of the precipitated nano-Cr phase is combined with the C element in WC to form nano-Cr23C6. Both nanophases can improve the resistance to dislocation and sub-grain boundary movement in the deformation process of WC/CuCr30 composite, thus improving the hardness of the copper matrix with a slight decrease in electrical conductivity. The results of electrical contact show that the addition of WC particles and nano-Cr precipitates can not only extend contact life of CuCr material, but also help to disperse the arc to avoid concentrated erosion. The presence of Cr23C6 phase around WC particles effectively improves the interfacial bonding between Cu phase and WC phase and reduces the probability of pore existence at the interface, which is beneficial to vacuum breaking performance.

The Influence of Mechanical Deformation Consideration on the Results of the Calculation of the Vacuum Circuit Breaker Drive Shaft

One of the important directions of theoretical, computational and experimental research related to the improvement and development of new design elements of modern electrical devices, primarily medium voltage circuit breakers and contactors, is the study of not only electromagnetic, but also mechanical processes in these electrical devices. The paper is devoted to the creation and use of computational models for calculating mechanical forces and deformations of an absolutely rigid and real drive shaft of a medium voltage vacuum circuit breaker in static mode with the aim of quantitative comparison of the obtained numerical results. Calculation studies are performed using the finite element method. A comparative analysis of the calculation of mechanical stresses in the drive shaft of a vacuum circuit breaker in a static mode for an absolutely rigid and real shafts is carried out in this paper on the basis of the developed models. The obtained results of computer modeling are given in detail in tabular and graphic forms, including the shape of the deflection of the medium voltage vacuum circuit breaker shaft at the maximum stroke of the actuator of the electrical device under study. It has been demonstrated that the mechanical deformation of the shaft causes a decrease in contact drop and contact pressure forces, but with a correctly selected cross-section, these values are not critical and have little effect on the circuit breaker operation (about 20% and 7%, respectively). It is shown that as a result of shaft bending, additional axial forces appear in the supports, which significantly affect the choice of bearings according to the equivalent static load.

Dynamic Model of Medium Voltage Vacuum Circuit Breaker and Induction Motor for Switching Transients Simulation Using Clark Transformation

A derivation of the dynamic model of a medium voltage vacuum circuit breaker and induction motor in space vectors in coordinates αβ0 allow us to model switching transients in various dynamic states of the motor. In the case of the Clark transformation, the corresponding numerical integration technique can be selected including variable time-step integration techniques to avoid numerical instabilities due to the stiffness of the system. Assymetrical operations such as switching cause the power system to become unbalanced and the transformed equations α, β, and 0 are not uncoupled. Therefore, it is necessary to derive a coupling matrix between circuit breaker voltages and currents in the coordinate system αβ0. The subject of our interest is switching overvoltages that arise when turning off small inductive currents by a vacuum circuit breaker. When deriving the model of a vacuum circuit breaker, all its properties encountered during this action are taken into account, i.e., current chop, virtual current chop, dielectric barrier in the circuit breaker and its recovery rate, and the ability of the vacuum circuit breaker to extinguish high frequency currents. Simulation results are compared with the measured results on a medium voltage motor as well as with the simulation results of the mathematical model of the test circuit according to IEC 62271-110 resolved using the nodal method (EMTP algorithm). Models are implemented in the MATLAB/Simulink programming environment.

Interpretation of NSDD and Restrike in Capacitive Current Switching Test on Medium Voltage Vacuum Circuit Breaker

Capacitor banks are installed in an increasing number to control power quality issues and improving the power factor tocounteract the reactive power in the transmission and distribution networks. Due to load fluctuations switching of capacitorbanks is a typical phenomenon. Capacitor bank is normally having concentrated capacitance in contrast with distributedcapacitance. It generally draws more current than unloaded cableor line in practical cases up to several hundred amperes.Hence, switching of capacitor bank causes a very high rate of rise of transient recovery voltage across circuit breakercontacts. This scenario can be simulated in testing laboratories by a voltage source connected to a circuit breaker whichagain is connected to a large capacitance in terms of IEC called capacitive current switching test. Non-sustained disruptivedischarge (NSDD) is a voltage breakdown after the vacuum circuit-breaker open the fault current which will not cause therecovery of power frequency current. Restrike is different from NSDD, the recovery of power frequency current betweenthe contacts will make the breaker failed. It’s not easy to show the distinction between NSDD and restrike during some typetests. The paper presents the study of performance evaluation of the circuit breaker during the capacitor current switchingduties. A statistical analysis of failure of circuit breaker during capacitor current switching tests are included in the paperto help the manufacturers & utilities, so that the care can be taken for trouble free services. The paper also discusses thechanges made in the IEC 62271 – 100, Amendment1:2012 for conducting the capacitive current switching tests.

Innovative sensors for smart medium voltage vacuum circuit breaker

The paper explains the principle of the “Mechanism Monitoring” and “Vacuum Interrupter erosion monitoring” for a smart Vacuum Circuit Breaker, as well as gives the information about the sensor used for this monitoring.

Novel distribution transformer design for data center applications resilient to transient voltage stresses generated by VCB operation

Dry-type distribution transformers in modern data centres are usually protected by medium voltage (MV) vacuum circuit breakers (VCB). The interaction between VCB, MV cables, and dry-type transformers were studied extensively due to some catastrophic failures of the transformer primary windings, which have had a significant impact on data center up-time. It was observed that VCB switching events can initiate series and parallel resonances in transformer windings, as well as prestrike/restrike overvoltages at transformer terminals. In this work, a novel transformer design concept is presented, based on the shifting of natural transformer series resonance frequencies above the range of the expected frequencies common to operation of VCBs. This novel design has been confirmed by standard manufacturing tests, as well as novel special testing procedures replicating the real-life equipment installations in data centres.

Medium voltage vacuum circuit breaker with per phase electromagnetic actuator

In medium voltage vacuum circuit breakers, in order to achieve an even distribution of force along the entire length of the drive shaft, the drive mechanism is made per phase, that is, a separate electromagnet is installed under each pole. The analysis of designs and features of operation of vacuum circuit breakers with a per phase electromagnetic drive is carried out. Deficiencies in the designs of these drives have been identified. The design of a vacuum circuit breaker with a per phase electromagnetic drive and a kinematic diagram of the operation of a vacuum circuit breaker with a monostable polarized electromagnet and a return spring during the closing operation are considered. As a per phase drive, it is proposed to use three monostable polarized electromagnets with return springs, which makes it possible to reduce the overall dimensions of not only the drive electromagnet, but also the vacuum circuit breaker. Moreover, the return spring is not included in the design of the proposed electromagnet, but is part of the circuit breaker drive mechanism. The design of the housing of the vacuum circuit breaker with a per phase drive and a synchronizing shaft has been developed, which makes it impossible for the non-simultaneous closing and opening of the main contacts when performing switching operations. The calculation of a monostable polarized electromagnet is carried out and the possibility of its use as a per-phase drive in a medium voltage vacuum circuit breaker is confirmed.

Analysis of the operation of the drive mechanisms of medium voltage vacuum circuit breakers

Analysis of the operation of the drive mechanisms of medium voltage vacuum circuit breakers

INVESTIGATIONS OF THE DYNAMICS OF A BISTABLE ELECTROMAGNET WITH IMPROVED CHARACTERISTICS FOR MEDIUM VOLTAGE VACUUM CIRCUIT BREAKERS

Introduction. Currently, for switching medium voltage circuits, vacuum circuit breakers are widely used, which have good arcing properties and high breaking capacity. One of the problems of creating the drive mechanism of such apparatus is the need to ensure the absence of contact welding when a through current of a short circuit of a given duration flows through them, which is achieved due to a certain amount of contact pressure. One of the problems arising in the design of circuit breakers is the need to fix the mechanism with a mechanical lock, which should hold the mechanism securely. This leads to significant specific mechanical loads, which in turn reduces the reliability of the circuit breaker. One way to solve these problems is to create a drive based on monostable or bistable electromagnetic actuators with highly coercive permanent magnets, which provide reliable fixation of the position of the contacts. Purpose. Investigation of the improved design of a bistable electromagnetic actuator based on permanent magnets of a medium voltage vacuum circuit breaker. Methods. Theoretical and experimental research and comparative analysis of existing and developed electromagnetic actuators. Conclusions. A new design of an electromagnetic bistable actuator with reduced overall dimensions is developed and tested. The electromechanical characteristics of the actuator correspond to the technical specifications, which is confirmed by both theoretical and experimental studies. The proposed actuator can be used as a drive mechanism for medium voltage vacuum circuit breakers.

Investigations of the Dynamics of a Bistable Electromagnet with Improved Characteristics for Medium Voltage Vacuum Circuit Breakers

Introduction: Currently, for switching medium voltage circuits, vacuum circuit breakers are widely used, which have good arcing properties and high breaking capacity. One of the problems of creating the drive mechanism of such apparatus is the need to ensure the absence of contact welding when a through current of a short circuit of a given duration flows through them, which is achieved due to a certain amount of contact pressure. One of the problems arising in the design of circuit breakers is the need to fix the mechanism with a mechanical lock, which should hold the mechanism securely. This leads to significant specific mechanical loads, which in turn reduces the reliability of the circuit breaker. One way to solve these problems is to create a drive based on monostable or bistable electromagnetic actuators with highly coercive permanent magnets, which provide reliable fixation of the position of the contacts. Purpose: Investigation of the improved design of a bistable electromagnetic actuator based on permanent magnets of a medium voltage vacuum circuit breaker. Methods. Theoretical and experimental research and comparative analysis of existing and developed electromagnetic actuators. Conclusions: A new design of an electromagnetic bistable actuator with reduced overall dimensions is developed and tested. The electromechanical characteristics of the actuator correspond to the technical specifications, which is confirmed by both theoretical and experimental studies. The proposed actuator can be used as a drive mechanism for medium voltage vacuum circuit breakers.

Analysis of average-closing-speed for medium-vacuum circuit breaker from theoretical calculation aspects

Average closing speed is an important indicator for evaluating the performance of CB, in order to calculate the average closing speed of the spring operating mechanism of the medium voltage vacuum circuit breaker, the paper establishes a simplified model of CB mechanism, combined with the kinetic energy theorem, and obtains the average closing speed by analyzing the equivalent mass and energy of the mechanism. In order to verify the correctness of the proposed method, the paper establishes a CB simulation model to obtain the simulated average closing speed. In the calculation of the energy of the open-off phase, the paper adopts a segmentation calculation method, which divides the closing process into the open-distance phase and the over-travel phase, and the calculated average closing speed is more accurate. This theoretical calculation method provides a theoretical basis for the research and development of the medium-voltage vacuum CB spring operating mechanism, and plays a positive role in related research and development work.

Simulation Analysis for Opening Performance of Medium Voltage Vacuum Circuit Breaker Based on ADAMS and Maxwell

The circuit breakers play a important role in control and protect the power systemand the vacuum circuit breaker has beenwidely used in the field of medium voltage with its excellent opening performance.Virtual prototyping technology is alsobecamemore and more popularin design and optimization of the vacuum circuit breaker. In this paper, the electromagnetic simulation software Ansoft Maxwell is used to analyze the electric repulsion of the circuit breaker in the case of open the rated short circuit breaking current. The 3D model that wasbuilt by CREOis imported into ADAMS. Thenconstraints, contact force, and the electric repulsion forcethat was analysezed in Ansoft Maxwell is added into the 3D model.Therefore, we can carry on the multi-body dynamics simulation to the 3D model. Then We can get the openingperformance of the vacuum circuit breakerin the condition of open circuit rated short circuit breaking current. The simulation results show that the circuit breaker can still meet the performance requirements in the condition of open circuit rated short circuit breaking current.

A Permanent Magnetic Actuator for 126 kV Vacuum Circuit Breakers

Permanent magnetic actuators (PMAs) have been widely used in medium-voltage vacuum circuit breakers (VCBs) due to their high reliability and controllability. However, a conventional bistable PMA cannot be adopted in power equipment for the transmission voltage level such as 126 kV VCBs directly because of its low-velocity characteristics. The objective of this paper is to propose a multimagnetic circuit PMA to satisfy the high-velocity requirements for 126 kV VCBs. The novel PMA is a bistable and axisymmetric structure, including holding and driving components whose magnetic circuits are separated. Air gaps are specifically designed in the magnetic circuits to improve the velocity performance of the novel PMA. Both static and dynamic characteristics of the novel PMA model have been calculated through finite-element software coupled with multi-body dynamics software. Furthermore, a prototype of the PMA has been developed according to the calculation results. The experimental results on the prototype have shown that the velocity characteristics of the PMA are able to meet the requirements of a 126 kV VCB and agree well with the simulation results.

Design and Analysis of a New Permanent Magnet Actuator for Medium Voltage Vacuum Circuit Breakers

This paper proposes a bi-stable permanent magnetic actuator (PMA) for medium voltage vacuum circuit breaker. The structure of the proposed PMA is discussed and the optimization of the structure is carried out. The model of finite element analysis (FEA) is constructed where the flux distributions, electromagnetic force under different structure parameters are analyzed. The feasibility and correctness of the PMA are verified by the FEA simulation results and the optimal size for movable plunger and stationary iron ring is obtained.

Understanding Circuit Breaker Design and Operation to Improve Safety and Reliability in Underground Mining

Traditional “above-ground” applications of circuit breakers for overcurrent protection in industry are generally well understood. Defined design and test standards, which vary somewhat across the globe, provide a framework for users of these devices to assure that they are not misapplied. Attention to detail in circuit breaker maintenance generally assures that these devices will operate reliability and safety across the industry. However, when circuit breakers are applied in underground mining applications, traditional design and test standards give way to in-country mining safety authorities who typically dictate requirements in these special applications. Because of this, ratings and test requirements for low-voltage molded-case circuit breakers, low-voltage power circuit breakers, medium-voltage vacuum and medium-voltage sulphur hexafluoride (SF6) circuit breakers in underground mining are typically different. In this environment, the user must be aware of issues specific to the application to assure that these devices operate such that they assure miner safety and operation reliability. This paper will discuss specific circuit breaker applications in underground mining and recommend methods to maximize the effectiveness of these protective devices in this environment.

The control of polarized bistable electromagnetic actuators of medium voltage vacuum circuit breakers

A brief review of the market of vacuum circuit-breakers for medium voltage networks is given. Some designs of electromagnetic actuators of these devices, as well as electromechanical and microprocessor-based units for controlling bistable polarized actuators, are considered.

Analyses of mechanical characteristics of vacuum circuit breaker during the closing process taking electrodynamic force into account

A dynamic model for the closing process of a medium-voltage vacuum circuit breaker (MVVCB) is constructed, and the automatic dynamic analysis of mechanical system software is applied to construct the model by taking electrodynamic force into account. After the electrodynamic force is worked out, the model is employed to investigate the mechanical characteristics during the closing process of a MVVCB under the influence of electrodynamic force. The characteristics are also investigated through experiment. Moreover, the simulation and experimental results are in close agreement. The results show that the electrodynamic force not only reduces the moving speed of the main axle's angle to a certain degree but also influences the four parameters used to describe the performance of mechanical characteristics. The simulation and experimental results presented here can be used to highlight the design criteria on the optimal operation and condition monitoring of MVVCBs.

Mechanical Condition Recognition of Medium-Voltage Vacuum Circuit Breaker Based on Mechanism Dynamic Features Simulation and ANN

A new research method is proposed for the medium-voltage (MV) vacuum circuit breaker's (CB's) mechanical condition monitoring, which combines the mechanism dynamic features simulation and mechanical condition recognition algorithm based on artificial neural networks (ANNs). This method includes three steps: First, the relations between eigenvalues and mechanical failures of a vacuum circuit breaker (CB) through simulation instead of measurement are obtained. In this paper, the mechanism dynamic features of a vacuum CB in failure are simulated; the simulation results indicate that the parameter that can be monitored-main angle-has different characters for different mechanism failures. Second, the eigenvalues for different failure conditions are described by three parameters. Third, mechanical condition recognition of the MV vacuum CB by an algorithm based on ANN is realized. It is concluded by the work mentioned above, both the known mechanical condition type and the new mechanical condition type of the medium-voltage vacuum CB can be recognized with predetermined reliability.

Theoretical and experimental analyses of the mechanical characteristics of a medium-voltage circuit breaker

A dynamic model for a medium-voltage vacuum circuit breaker is constructed using the ADAMS software. The model is used to investigate the mechanical characteristics of the circuit breaker under the influence of electrodynamic forces. The characteristics are also investigated experimentally. The simulated and experimental results are in close agreement. It is shown that electrodynamic force increases the breaking speed of the moving contacts by 0.2 m/s. The model can be used to highlight design criteria for the optimal operation of medium-voltage circuit breakers.

A statistical vacuum circuit breaker model for simulation of transient overvoltages

A statistical model of a medium voltage vacuum circuit breaker was developed in EMTP by using new powerful TACS MODELS. The model includes the arc voltage characteristic, calculation of mean chopping current value with known di/dt, the dielectric breakdown voltage characteristic, contacts separation dynamics, probability of high frequency arc quenching capability and probability of high frequency (HF) zero current passings. The influence of a switching-off time is studied and a statistical estimation is given of the transient overvoltages expected for a specific network configuration. The relation between the switching-off times and the overvoltages is also presented. In addition to these results the paper includes explanation of the modeling technique in the EMTP for all elements constituting the distribution network and validation of the vacuum breaker model behavior. This approach provides valuable information to engineers constructing metal-enclosed switchgear, electric utilities and other users who are going to install vacuum breakers in medium voltage networks. >