Abstract –
This paper presents the work that is beingdone as a part of the ByFault project (Brite/Euramprojet finaced by the European Community):manufacturing, modelling and simulation of aSuperconducting Hybrid Fault Current Limiter(SHFCL). The SHFCL is based on a variableimpedance transformer: primary winding is in serieswith the protected line and several secondaries areshort-circuited by superconducting elements. Thistopology has been modelled using 2-D and 3-D finiteelements, and some useful formulation to simulate thebehaviour of the SHFCL has been obtained. TheSHFCL's integration with the electrical network hasbeen simulated using several tools (ATP-EMTP, PSS/Eand Power System Blockset of Matlab), depending onthe application and the desired location voltage.Keywords: Superconducting fault current limiter,manufacturing, modelling, bus-bar connectionI.
INTRODUCTION
The main idea behind a High Vo ltage SuperconductingFault Current Limiter (HVSFCL) is that in normal state(superconducting state) the HVSFCL has an almostnegligible impedance while during the fault, the existenceof high currents induces the lost of the superconductingstate and the HVSFCL's impedance increases abruptly. Theadvantage of this kind of device face to the classicalcurrent limiter resides in its very fast operation capabilitywith a real current peak limitation.One of the planned HVSFCL will be resistive [1]. Asuperconducting element is placed in series with thenetwork, showing a zero-impedance behaviour duringnormal state and a current limiting resistance during thefault. The second planned HVSFCL will be hybrid [2]. TheSHFCL is based on a variable impedance transformer:primary winding is in series with the protected line andseveral secondaries are short-circuited by superconductingelements. As the flux is constrained to zero in normal statethe impedance of the primary is composed only by leakageinductance. In a fault occurrence case the resistance of allthe secondaries increase and a current limiting inductivebehaviour (due to the magnetising inductance) is observedfrom the primary.Both HVSFCL have been successfully tested in alaboratory environment. In order to insert the device in aMV network previous theoretical study and simulations areneeded. This paper describes some of this previous workrelated to the hybrid HVSFCL, including manufacturing,modelling, simulations and location choice.II. SHFCL DESCRIPTIONThe practical configuration of the One-Phase HybridLimiter is in the form of a toroidal transformer (Fig. 1),with the superconducting bars short-circuiting its Nsecondaries, and the primary connected in series to thenetwork to be protected. Each secondary is a shortcircuitedring formed by the series interconnection of asuperconducting bar and a copper ring.Network lineprimarysuperconductorbarscopper ringNsecondariesiron yokeFig. 1. General Scheme of the SHFCL.The superconductor is melt textured YBCO 123 [2] inthe shape of small rods which are cut to match the requireddimensions. As the superconductor is working at 77K, allthe secondary must be placed inside a cryostat. The factthat the copper of this winding is working at cold reducesconsiderably its electrical resistance and helps to achieve alower impedance of the limiter at no-fault condition.The device is placed in series with the network: in theevent of a fault, when the primary current exceeds a certainvalue, the current through each bar will grow beyond theso called critical current and the superconductor will startto transit to the resistive state. Triggering current of thelimiter is defined by the transforming ratio of the limiterand the critical current of the bars.Fig.



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