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  • 1.
    Augustin, Tim
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Parekh, Mrunal
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Magnusson, Jesper
    ABB.
    Becerra Garcia, Marley
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. ABB.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Thomson-Coil Actuator System for Enhanced Active Resonant DC Circuit Breakers2022In: IEEE Journal of Emerging and Selected Topics in Power Electronics, ISSN 2168-6777, E-ISSN 2168-6785, Vol. 10, no 1, p. 800-810Article in journal (Refereed)
    Abstract [en]

    Enhanced active resonant (EAR) dc circuit breakers (DCCBs) are a promising set of recently proposed DCCB concepts. As other DCCBs, EAR DCCBs still require a fast mechanical switch. The requirements on the actuator of the mechanical switch depend on the DCCB concept and the dc grid and are derived here for an EAR DCCB. Thomson-coil actuators (TCAs) can open and close mechanical switches sufficiently fast to satisfy the requirements. This work studies experimentally a TCA system with active damping for an off-the-shelf industrial vacuum interrupter used as mechanical switch in an EAR DCCB. The prototype is explained in detail, and extensive measurement results are presented, showing that active damping must be perfectly timed to be effective. A novel Thomson-coil (TC) driver is proposed and studied experimentally, which operates the TCA more efficiently by recycling energy during the actuation. Moreover, the novel TC driver reduces the capacitive storage by 50% and allows for faster recharging with lower charging current. Finally, the autoreclosing and proactive commutation operation of the TCA system and the interruption capability of the prototype EAR DCCB are demonstrated experimentally.

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  • 2.
    Parekh, Mrunal
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Magnusson, Jesper
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. ABB.
    Engdahl, Göran
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Becerra Garcia, Marley
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Arc Characteristics of Ultra-Fast Opening Switching Contacts in Hybrid Breakers2021In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 36, no 5, p. 2872-2880Article in journal (Refereed)
    Abstract [en]

    A mechanical switch can be used instead of a power electronic load commutation switch to reduce losses during normal power flow in standard hybrid DC breakers. The success of current commutation in such hybrid breakers depends on the arc voltage across the contacts of the mechanical switch. The behaviour of rapidly elongated arcs generated during the opening of an ultra-fast mechanical switch in the air is studied here. The voltage-current characteristics of the generated arcs are obtained for contact opening velocities of 6, 11 and 21 m/s. It is found that the arc voltage at a given current and contact separation increases with contact opening velocity. It is shown that stationary, zero-contact-velocity characteristics can not be used to accurately quantify the voltage build-up in fast elongating arcs in hybrid breakers. A best-fitting black-box the equation for the dynamic arc characteristics is presented for the tested velocities. The obtained voltage-current characteristics are used as input to simulate the current commutation process in a 12 kV hybrid DC circuit breaker case-study. Different scenarios of current commutation failure related to the arc voltage build-up are identified. It is shown that these failures scenarios can be avoided by increasing the contact opening velocity.

  • 3.
    Wetula, Andrzej
    et al.
    AGH Univ Sci & Technol, Fac Elect Engn Automat Comp Sci & Biomed Engn, Al Mickiewicza 30, PL-30059 Krakow, Poland..
    Bien, Andrzej
    AGH Univ Sci & Technol, Fac Elect Engn Automat Comp Sci & Biomed Engn, Al Mickiewicza 30, PL-30059 Krakow, Poland..
    Parekh, Mrunal
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    New Sensor for Medium- and High-Voltage Measurement2021In: Energies, E-ISSN 1996-1073, Vol. 14, no 15, article id 4654Article in journal (Refereed)
    Abstract [en]

    Measurements of medium and high voltages in a power grid are normally performed with large and bulky voltage transformers or capacitive dividers. Besides installation problems, these devices operate in a relatively narrow frequency band, which limits their usability in modern systems that are saturated with power electronic devices. A sensor that can be installed directly on a wire and can operate without a galvanic connection to the ground may be used as an alternative voltage measurement device. This type of voltage sensor can complement current sensors installed on a wire, forming a complete power acquisition system. This paper presents such a sensor. Our sensor is built using two dielectric elements with different permeability coefficients. A finite element method simulation is used to estimate the parameters of a constructed sensor. Besides simulations, a laboratory model of a sensor was built and tested in a medium-voltage substation. Our results provide a proof of concept for the presented sensor. Some errors in voltage reconstruction have been traced to an oversimplified data acquisition and transmission system, which has to be improved during the further development of the sensor.

  • 4.
    Parekh, Mrunal
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Ultra-fast electromechanical commutation switch for hybrid breakers2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In a power system with the ability to integrate geographically spread diverse renewable energy sources, there is a need for efficient control of the power flow and effective power transmission. Power electronics can provide this controllability, at the expense of conductive losses in the used components. These losses can be reduced substantially by the use of ultra-fast electromechanical switches in parallel with power semiconductor devices, known as hybrid breakers. There are three major requirements for such breakers. They should i)  have higher mechanical and electrical operations, ii) have sufficient and rapid arc voltage build up to facilitate successful current commutation into parallel power semiconductor and iii) be able to withstand the transient interruption voltage. 

    An ultra-fast electromechanical switch is operated with a Thomson coil based electromagnetic actuator. This actuator can generate a sufficient force and swiftly open electrical contacts in a couple of milliseconds. Since contacts are opening with high velocities, there is a need for timely and controlled damping to secure a long lifetime of the device. Different eddy current based damping actuator concepts are presented in this thesis. Modelling using the finite element method is accompanied by experimental results to study the effect of load mass attached to the actuator and incoming velocities. It was observed that the magnetic field component perpendicular to the direction of the contact movement is key in achieving high damping forces. Higher damping forces are achieved if the magnitude of this magnetic field is high and has a uniform distribution.

    The success of current commutation in hybrid breakers depends on the arc voltage formed across the contacts in an ultra-fast switch. Towards that, the behaviour of rapidly elongating arcs generated during the opening of an ultra-fast mechanical switch in the air is also investigated in the thesis. The voltage-current characteristics of the arc generated between the contacts of a model ultra-fast commutation switch are obtained for different contact opening velocities. It is found that at a given current and contact separation, the arc voltage increases with the contact opening velocity. It is also shown that stationary, zero-contact-velocity characteristics can not be used to accurately quantify the voltage build-up in fast elongating arcs in hybrid breakers. Furthermore, the obtained arc characteristics are used as input to simulate the current commutation process in a medium voltage hybrid DC circuit breaker case study. Different failure scenarios of current commutation related to the arc voltage build up are identified. It is shown that these failure scenarios can be avoided by increasing the contact opening velocity. Finally, a 2D axisymmetric magneto-hydrodynamic model of a rapidly elongated arc plasma in the air is presented in the thesis. It is observed that convective cooling dominates over other cooling mechanisms. The magnitude of the convection cooling is higher for higher contact opening velocity, immediately after the contact opening.

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  • 5.
    Parekh, Mrunal
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Bissal, Ara
    Magnusson, Jesper
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. ABB AB Corporate Research, Västerås 722 26, Sweden.
    Engdahl, Göran
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Design of a linear Halbach magnetic damper2018In: International journal of applied electromagnetics and mechanics, ISSN 1383-5416, E-ISSN 1875-8800, Vol. 59, no 2, p. 1-9Article in journal (Refereed)
    Abstract [en]

    Ultra-fast circuit breakers are operated with fast electromagnetic actuators. They can generate a sufficient impulse force to swiftly open electrical contacts in a couple of milliseconds. Opening of the contacts with high velocities implies a need for a timely and controllable damping. An efficient damping mechanism then is crucial to attain an appropriate actuation performance and secure a long lifetime. In this paper a finite element model of a Halbach magnet array based magnetic damper and a corresponding experimental prototype is described. A parametric study is performed to understand the effect of load mass and incoming velocities. It was found that the magnetic field modulation plays an important role on the damping performance. A uniform and high radial component of the magnetic flux density is necessary in order to achieve high damping force. The radial magnetic field can be controlled via thickness and magnetization direction of the ring magnets that are used to create the Halbach magnet array.

  • 6.
    Parekh, Mrunal
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Magnusson, Jesper
    ABB AB Corp Res, S-72226 Västerås, Sweden..
    Becerra Garcia, Marley
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. ABB AB Corp Res, S-72226 Västerås, Sweden.
    Engdahl, Göran
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Effect of contact velocity on the behaviour of decaying arcs in air2018In: PROCEEDINGS OF 2018 29TH INTERNATIONAL CONFERENCE ON ELECTRICAL CONTACTS AND 64TH IEEE HOLM CONFERENCE ON ELECTRICAL CONTACTS, IEEE , 2018, p. 77-80Conference paper (Refereed)
    Abstract [en]

    Hybrid direct current circuit breaker (HDCCB) consists of an ultra-fast electromechanical switch combined with power semiconductors to interrupt fault currents. When the ultra-fast electromechanical switch opens, arc plasma is generated between its contacts that commutate the fault current to the auxiliary circuit consisting of power semiconductors. Understanding of the arc behaviour due to the ultra-fast contact opening is necessary as the current commutation is driven by the arc voltage. This paper presents experimental results of a dynamic voltage-current (V-I) characteristics of a decaying arc plasma in air having contact opening velocities from 5 to 15 m/s. A pair of hemispherically capped copper contacts was used for the experiments. The contacts were covered by a glass tube, open from one end which makes the arc partially wall constricted. The contacts were opened with a dedicated Thomson coil based electromagnetic actuator. A computer controlled test system was used that allowed controlling the shape of the current pulse and the time instant of the contact opening on the current waveform. The conductance of the arc was calculated for different contact opening velocities. It was observed that the conductance decreased with an increase of the contact opening velocity. High speed imaging was performed to observe the physical behaviour of arcs having different contact opening speeds.

  • 7.
    Parekh, Mrunal
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Electrical Engineering and Computer Science (EECS).
    Magnusson, Jesper
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. ABB AB Corporate Research, Västerås.
    Engdahl, Göran
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Study of an Electromagnetic Damping Actuator2018In: VDE Conference Proceedings on Actuator 18, 2018, p. 475-478, article id P25Conference paper (Refereed)
    Abstract [en]

    Current commutation switches for HVDC devices are operated with Ultra-fast electromagnetic actuators. They can generate hundreds of kilo-newton force and swiftly open electrical contacts in a couple of milliseconds. An efficient damping mechanism then is crucial to attain an appropriate actuation performance and secure a long lifetime. In this article an electromagnetic Halbach damping actuator was studied. A numerical model based on FEA is used to calculate its damping constant and retardation time down to stand still velocity.

  • 8.
    Augustin, Tim
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Becerra Garcia, Marley
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Magnusson, Jesper
    ABB Corporate Research, Västerås.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Parekh, Mrunal
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    System Design of Fast Actuator for Vacuum Interrupter in DC Applications2018In: 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV), Institute of Electrical and Electronics Engineers (IEEE), 2018, Vol. 2, p. 527-530Conference paper (Refereed)
    Abstract [en]

    One of the major challenges of DC circuit breakers is the required fast mechanical actuator. In this paper, a Thomson coil actuator system for a vacuum interrupter is designed. Active damping is used to decelerate the moving contacts. Challenges are discussed, especially concerning the power supply needed for the Thomson coil actuator. The design philosophy is explained and FEM simulation results are presented. The results indicate that a wide range of combinations of drive circuit capacitance and voltage fulfill the requirements for armature acceleration. However, active damping requires a very careful selection of drive circuit voltage and timing of applied damping.

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  • 9.
    Parekh, Mrunal
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Bissal, Ara
    ABB AB Corporate Research, Västerås, Sweden.
    Magnusson, Jesper
    ABB AB Corporate Research, Västerås, Sweden.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Study of a linear Halbach passive magnetic damper2017In: 2017 IEEE International Magnetics Conference, INTERMAG 2017, Dublin, Ireland: IEEE conference proceedings, 2017, article id 8008035Conference paper (Refereed)
    Abstract [en]

    High voltage ultra-fast circuit breakers are operated with fast actuators. They are capable of generating impulsive force to swiftly open electrical contacts in a couple of milliseconds. Opening of the contacts with high velocities implies a need for a timely and controllable damping. An efficient damping mechanism then is crucial to attain an appropriate actuation performance and secure a long lifetime. In this paper a finite element model of a Halbach magnet array based magnetic damper and a corresponding experimental prototype is described. It was found that a uniform and high radial component of the magnetic flux density is necessary in order to achieve high damping force. The radial magnetic field can be controlled via thickness and magnetization direction of the ring magnets which are used to create the Halbach magnet array. Finally, it is also shown that the concept provides a frictionless collision free damping demonstrating its potential to be used in fast circuit breakers.

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