Medium Voltage Circuit Breakers Research Articles

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.

Fault Diagnosis of Medium Voltage Circuit Breakers Based on Vibration Signal Envelope Analysis.

In modern power systems or new energy power stations, the medium voltage circuit breakers (MVCBs) are becoming more crucial and the operation reliability of the MVCBs could be greatly improved by online monitoring technology. The purpose of this research is to put forward a fault diagnosis approach based on vibration signal envelope analysis, including offline fault feature training and online fault diagnosis. During offline fault feature training, the envelope of the vibration signal is extracted from the historic operation data of the MVCB, and then the typical fault feature vector M is built by using the wavelet packet-energy spectrum. In the online fault diagnosis process, the fault feature vector T is built based on the extracted envelope of the real-time vibration signal, and the MVCB states are assessed by using the distance between the feature vectors T and M. The proposed method only needs to handle the envelope of the vibration signal, which dramatically reduces the signal bandwidth, and then the cost of the processing hardware and software could be cut down.

Medium-Voltage Circuit Breakers and Contactors Are Not the Same: Neither are Their Protection Methods

Many standards and specifications related to medium-voltage (MV) motor and feeder circuits continue to center around the improper generic use of IEEE Device 52 as a circuit identifier for the switching device used within various points of power systems. IEEE Device 52 is defined as a device that is used to close and interrupt an ac power circuit under normal conditions or to interrupt this circuit under fault or emergency conditions. While many of the present standards include detailed protection and coordination recommendations that are centered only on the protective and control settings for circuit breakers (CBs), the protection schemes for CBs and fused contactor-controlled motors are documented in IEEE Standard 3004.8. This article clarifies some key differences between MV contactors and MV CB ratings. It also compares the appropriate protection variations and requirements between the two devices, highlighting the dangers to personnel and equipment if misapplied. Recommended protective device functions for motor protection for fused contactor-controlled or breaker-controlled motors are presented with companion drawings.

Modeling and normative instructions for the application of EMT-based programs in the evaluation of medium voltage circuit-breakers in a real industrial system

This paper aims to present a guideline for modeling and normative instructions for short-circuit (SC) and transient recovery voltage (TRV) analysis of medium voltage circuit-breakers installed in a real industrial system. The Alternative Transient Program (ATP) through its graphical interface ATPDraw was used in the work. The criteria used for modeling the analyzed industrial system are presented in detail. For a better understanding of the technical information required for the modeling employed in TRV and SC studies, a set of detailed and typical data used is presented in order to contribute to the reproduction of this case study in other expanding industrial power systems. The instructions for SC and TRV evaluation of circuit-breakers are based on the limits described by IEC standards and other references. The results are presented by discussing the effects of industrial expansion on the evaluated medium-voltage circuit breakers.

A Solid-State Circuit Breaker Without Current Limiting Inductor

This paper presents a high-density, high-efficiency megawatt (MW) medium-voltage (MV) solid-state circuit breaker (SSCB) for aviation hybrid electric propulsion applications. The proposed SSCB is based on the mature silicon (Si) insulated gate bipolar transistor (IGBT) devices. With reduced IGBT gate voltage, the proposed SSCB can limit the peak fault current without the fault current limiting inductor. Thus, the specific power density of the SSCB is substantially improved compared with the traditional design. This method has negligible impact on SSCB efficiency, reliability and energy absorbed by the metal-oxide varistor (MOV), while providing additional mechanical layout freedom for power density and insulation enhancement. The potential design challenges due to the extremely high ramp rate of the system fault current and the corresponding solutions are also discussed. The performance of the proposed SSCB is validated with experimental results.

Fluid-chemical modeling of the near-cathode sheath formation process in a high current broken in DC air circuit breaker

When the contacts of a medium-voltage DC air circuit breaker (DCCB) are separated, the energy distribution of the arc is determined by the formation process of the near-electrode sheath. Therefore, the voltage drop through the near-electrode sheath is an important means to build up the arc voltage, which directly determines the current-limiting performance of the DCCB. A numerical model to describe the near-electrode sheath formation process can provide insight into the physical mechanism of the arc formation, and thus provide a method for arc energy regulation. In this work, we establish a two-dimensional axisymmetric time-varying model of a medium-voltage DCCB arc when interrupted by high current based on a fluid-chemical model involving 16 kinds of species and 46 collision reactions. The transient distributions of electron number density, positive and negative ion number density, net space charge density, axial electric field, axial potential between electrodes, and near-cathode sheath are obtained from the numerical model. The computational results show that the electron density in the arc column increases, then decreases, and then stabilizes during the near-cathode sheath formation process, and the arc column’s diameter gradually becomes wider. The 11.14 V–12.33 V drops along the 17 μm space charge layer away from the cathode (65.5 kV/m–72.5 kV/m) when the current varies from 20 kA–80 kA. The homogeneous external magnetic field has little effect on the distribution of particles in the near-cathode sheath core, but the electron number density at the near-cathode sheath periphery can increase as the magnetic field increases and the homogeneous external magnetic field will lead to arc diffusion. The validity of the numerical model can be proven by comparison with the experiment.

A Surgeless Diode-Clamped Multilevel Solid-State Circuit Breaker for Medium-Voltage DC Distribution Systems

In conventional medium-voltage solid-state circuit breakers (SSCBs), series-connected semiconductor switches are used with metal oxide varistors (MOVs) in parallel with each of them to extend the voltage ratings of the breakers without incurring the dynamic voltage unbalance. Besides, for isolating the faults at faster speeds, the clamped surge voltages of the MOVs are always much higher than the system voltages. For those reasons, the voltage ratings of all the switches in the SSCBs have to be overdesigned according to the surge voltage values, which causes high material costs along with nonideal conduction losses in the SSCBs employed for medium-voltage dc distribution systems. To solve this dilemma, a surgeless diode-clamped multilevel SSCB is proposed in this article. It offers an ultrafast isolation speed with no significant surge voltages or dynamic unbalanced voltage across the semiconductor switches. With these attributes, the proposed SSCB can potentially use the semiconductor switches rated at lower voltages compared to conventional SSCBs and have higher efficiency along with faster isolation speed. The simulation and experimental results are presented to validate the technical feasibility and practical values of the proposed SSCB.

A Systematic Robust Design Method to Reduce Products’ Environmental Impact Variations

Reducing the environmental impact of a device arising from unexpected failures should be an environmental goal. However, this problem can be difficult to tackle, especially due to the limitations of the traditional eco-design methods, which are more used to reduce the baseline impacts. This study proposes a novel method to overcome this limitation, working at the intersection of conceptual design, robust design, and eco-assessment. Based on the inquiry-based approach, the method consists of 52 questions, systematically organised on 4 hierarchical levels dedicated to the formulation of the initial environmental problem, the definition of the design goal, and the strategy and the selection of the methods, tools, and solutions to be applied. The method was applied in two real case studies about an adsorption air dryer and a medium-voltage circuit breaker by providing different solutions, where the most promising one was able to avoid the environmental impact variations up to 2% of the total impacts of the device. The method could be a starting point to build a design theory that is dedicated to this sector, still largely unexplored, while this vocation towards conceptual design is an appeal for a contamination of the more routine fields of robust and eco-design on the educational, application, and research levels.

Design and Research of Operating Repulsion Mechanism Suitable for 252kV High-Speed Breaking Circuit Breaker

This paper proposes a high-speed operating repulsive force mechanism suitable for 252kV high-voltage circuit breakers. The mechanism draws on the working principle of the electromagnetic repulsion operating mechanism of the medium voltage circuit breaker, and combines the new electromagnetic fast repulsion device with the traditional disc spring hydraulic mechanism to realize the fast action of the circuit breaker. This paper first introduces the working principle of the electromagnetic repulsion operating mechanism, and proposes the initial design scheme of the mechanism. Subsequently, the digital twin technology was used to establish the rigid-flexible coupling multi-body dynamics model of the mechanism, and the defects of the initial scheme were analyzed based on simulation. Finally, the paper optimized the design of the initial scheme and verified it by simulation. The test shows that the 252kV high-voltage circuit breaker with the improved scheme as the operating mechanism works normally and can complete the fault breaking within 20.1ms, which is twice as fast as the current products of the same type.

Generate Various Parameters Of Trv Envelope Synthetic Test Circuit

The most basic transient a circuit breaker needs to suffer during its activity is the transient recovery voltage (TRV), started by the electric force system as a characteristic response on flow interference. To test high voltage CBs, direct testing utilizing the force system or short out alternators are not practical. The testing of high voltage Circuit Breakers (CBs) of bigger limit requires huge limit of testing station. An equal infusion of short out current and transient voltage to medium and high voltage circuit breaker (CB) by a synthetic model is examined. Transient recovery voltage is made by a capacitor bank and is applied to CB. An optical set off spark gap has been utilized to interrupt short circuit and to introduce of transient recovery voltage that is applied across the contacts of circuit breaker. Transient recovery voltage examination can never be done totally, as the advancement of circuit breaker development and organization configuration goes on. The most widely recognized way to deal with TRV examination is concerning the supposed planned TRV, in which a suspicion of dismissing association between circuit breaker itself and the innate system recovery voltage is being made. Notwithstanding, it actually is by all accounts qualified to examine what circuit breaker means for transient recovery voltage. An ideal grouping to open/close of reinforcement test article and helper circuit breakers inside suitable chance to infuse of recovery voltage. The impact of reactance of inductive flaw current limiter just as distance to blame in short line issue condition on pace of ascent of recovery voltage. A 4-boundaries TRV synthetic test circuit dependent on equal current infusion technique is planned and mimicked for testing 145kV rating circuit-breakers according to new TRV prerequisites given in IEC 62271-100.

Partial Discharge Analysis of SF6/N2 Gas Mixture Filled MV Circuit Breaker Using Time–Frequency Map Clustering Technique

Breakdown of gas insulated switchgears due to partial discharges (PD) is a major threat for the safe and reliable operation of power system network. In recent times, PD based diagnostics has been widely adopted by electrical utilities in order to evaluate the health of high voltage insulation system. However, very few reports are only available on the PD characteristics of gas insulated medium voltage (MV) circuit breaker prototypes, in particular with mixture of gases, over a wide range of pressure and voltage stress. Deep analysis of nature of PD signals in mixture of gas insulation and its time–frequency characteristics is important in order to develop efficient online condition monitoring systems for circuit breakers. This paper is aimed at the analysis of PD characteristics of a 22 kV MV circuit breaker prototype filled with SF6/N2 gas mixtures using time–frequency (T-F) mapping and clustering technique. PD tests are carried out at different gas pressures (1–5 bar) and at different gas mixture ratios. Important PD parameters such as PD inception voltage, phase resolved PD (PRPD) pattern and PD repetition rate are evaluated. Clustering analysis of PD signals from the time–frequency mapping is carried out and formation of three different clusters consisting of short, long and repetitive PD pulses is identified. Online real time monitoring of individual cluster density will be helpful to understand the degradation of gas insulation of circuit breakers. Keeping in mind the minimal usage of SF6 gas, from the results, it is noted that 10% SF6 gas can be mixed with 90% N2 at 3 bar pressure to get satisfactory PD performance of a 22 kV medium voltage circuit breaker.

A reliable and efficient black box model of SF6 medium voltage circuit breakers

Several black-box models of circuit breakers have been proposed since the pioneering work by Cassie in 1943. Nevertheless, the nowadays need of a “further” black-box model is due to two main reasons: (i) accurate tools to simulate the complex physics that describes the interruption phenomena in circuit breakers are very cpu intensive and (ii) available black-box models tried to condense in few simple equations the complex physics of circuit breakers but they are inaccurate and do not cope with the full set of working conditions. We deal with SF6 medium voltage breakers proposing a model where the dynamics of the plasma and that of the breaker environment in which the electric arc develops (e.g., power dissipation, puffing, self-blasting) are separately modeled and then properly coupled. The result is an adequately accurate and fast black-box model that remains reliable in a wide set of working conditions as shown by comparisons of simulation and experimental results.

Replacement strategy of medium-voltage circuit breakers based on the segmented risk estimation

In this paper, a new replacement strategy for medium-voltage circuit breakers based on the segmented risk estimation of keeping them in service is presented. The methodology is based on the condition measurements of both circuit breakers and belonging feeders, and the assessment of risk of failure in the next period. The risk is divided into different operational conditions (normal and extreme) and different failure and feeder types. Normal risk deals with the probability of reaching the maximal allowed control value during normal operating conditions and the latter with the probability of reaching the maximal allowed number of short current interruptions in the next period. The total of 427 circuit breakers has been monitored, with data gathered in the past 10 years. After having administered the statistical tests, parameters for Weibull probability distribution of contact resistance for breakers on both overhead and underground feeders were determined. The probability of maximal number of interruptions is determined using the Poisson distribution. Finally, the risk estimation and replacement priorities are presented on the whole population of 427 breakers.

A 3-D Electrothermal Simulation of the Outdoor Medium-Voltage Circuit Breaker

This paper presents a three-dimensional electrothermal numerical model of the medium voltage outdoor circuit breaker. The model was validated by heat run test performed under the conditions required by IEC 62271-1 and IEC 62271-100 standards, as well as some other specific requirements related to the breaker overload under low ambient temperature conditions and natural cooling. The purpose of this study was to build a numerical model of the medium-voltage circuit breaker that could be successfully applied for the redesign of the breaker for more demanding operating conditions with minimum physical test iterations. The numerical results obtained were found to be in a good agreement with experimental values having the average discrepancy of 3 K with the maximum below 5 K on busbars.

Simulation and Experimental Investigation on a New Type of Cup-Shaped Contacts With Iron Cores

Vacuum interrupters, with the advantages of high breaking ability, small volume, low weight, and little pollution, are widely used in medium voltage circuit breakers. The transverse magnetic field (TMF), generated by spiral-type or cup-type contact, moves the constricted arc over the contact surface, which avoid excessive heating on the contact and reduce the erosion of a fixed area. The TMF contacts are slotted to cause current flow diversion, and a radial magnetic field is produced. In this paper, we propose an improved cup-type contact with iron cores. The magnetic field distribution of this new contact was simulated, and the magnetic force acted on arc column was calculated. It was found that the optimized contacts could effectively enhance the radial magnetic field between contacts and reduce the radial force of the arc column. In addition, two different kinds of cup-type TMF contacts were investigated in a demountable vacuum chamber using a high-speed charge-coupled device video camera. The experimental results suggested that compared with the traditional cup-shaped contacts, the new contacts could effectively improve the arc speed and duration of arc movement, accompanied by a more evenly surface ablation and an improved surface utilization.

Applying Arc-Resistant Technologies to Medium-Voltage Variable Frequency Drives

Arc resistant low/medium voltage switchgear and motor controls continue to provide proven levels of additional personnel safety in most every petroleum and chemical facility. The Institute of Electrical and Electronics Engineers (IEEE) and International Electrotechnical Commission (IEC) generated testing guides and standards for these products which are open to some level of interpretation when applied to products other than traditional medium voltage circuit breaker or fundamental motor controller structures for which the current available standards and guides were intended when they were initially written. All medium voltage variable frequency drives, because of their inherent designs, require high volumes of cooling air which pose a real challenge in regards to providing full arc resistant capabilities and compliance to the present testing guides, procedures, and standards. This paper will deliver real solutions to this problem through the application of unique cooling processes, arc channeling technologies, structural enhancements, arc fault energy limiting methodologies and special application considerations when applying arc resistant medium voltage drives.

Modeling and numerical simulation of anode activity and arc motion in a transverse magnetic field

Vacuum interrupters based on transverse magnetic field contacts now are widely used in medium voltage circuit breakers. The arc motion under the transverse magnetic field (TMF) plays a decisive role in the interruption. In this paper, we focus on the movement of vacuum arc driven by TMF and anode thermal process during the arcing. Then, based on the principle of conservation, a transient two-dimensional anode activity model (subjected to TMF constricted arc) is established. The state change of material, evaporation from contacts and motion of molten pool are also considered in our model. By considering the arc motion in the anode activity model, the transient anode thermal process and the movement of constrict arc under TMF are studied, respectively. The simulation predicted that average speed of arc is not higher than 200m/s. In the simulation, the anode surface is completely melted near the current peak with 200 μm molten layer. In addition, the influence of movement of molten pool on the arc speed is analyzed, finding that the movement of the bath accelerates arc speed, but weakens the surface melting at the same time.

DC vacuum circuit breaker

In the last years the progressive increase of distributed and non-programmable energy sources arise the interest in the use of DC for medium-voltage distribution systems. The study focuses on the design considerations of the apparatus required to support the management and protection of these applications. The fault-handling techniques in DC distribution system is introduced and the definition of the main requirements for the circuit breakers is supported by computer simulations of short-circuit current interruptions. A medium-voltage DC circuit breaker designed for 12 kV and 2.5 kA nominal current and 15 kA interrupted short-circuit current is presented. The functionalities and the performances are illustrated by means the experimental results obtained from high power tests.

Mastering all sub-assemblies of medium-voltage circuit-breaker and racking truck system ensures reliability and robustness

Mastering all sub-assemblies of medium-voltage circuit-breaker and racking truck system ensures reliability and robustness

Reducing Arc-Flash Hazards: Installing MV-Controllable Fuses on the Secondary Side of the Transformer in a Pumped Storage Plant

The Mitigation of arc-flash incident energy is important to increase safety. One method is to reduce the duration of the arc flash by using protective relays to sense an arc-flash fault. This method requires a supply-side switching device that will respond to the protective relaying fast enough to mitigate the incident energy. In many existing installations, medium-voltage (MV) controllable fuses are already installed to provide transformer protection. Before the development of an MV-controllable fuse, the MV fuse would have to be replaced with an MV circuit breaker or circuit switcher to have relay control of the MV protective device. This replacement would have significant equipment and construction costs and require extensive equipment outage time. The MV-controllable-fuse method uses the existing fusegear protecting the primary side of the transformer. The protective relay senses the arc fault and signals the controllable fuse to change to a fasteracting time-current response. The incident energies can be reduced from 200 cal/cm2 to lower than 8 cal/cm2 on the secondary side of the transformer. This article reviews an installation using an MV-controllable fuse to mitigate the incident energy on the equipment connected to the secondary side of the transformer.