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EN
Superconducting fault current limiters are the most attractive devices for the power network, they can be used to limit the short current in electrical network. The operation of a superconducting fault current limiter is based on the sudden transition from the superconducting state to the normal state by exceeding the critical current I_{c} of the material. This transition one takes a very short time, so fast that we are able to limit the first current peak to a threshold value which does not exceed three to five times the rated current. This paper presents the design, the calculated electrical parameters and tests of the medium voltage class superconducting fault current limiter prototypes made in Electrotechnical Institute. The constructed coreless superconducting fault current limiter consists of three windings: ones made of SF12050 tape and a parallel connected primary copper winding. All windings are inductively coupled and intended to work in liquid nitrogen.
EN
The oxide heterostructures composed of superconducting YBa_2Cu_3O_7 bottom layer, the overlying ferromagnetic La_{1-x}Sr_xMnO_3 film and SrTiO_3 as ultrathin (d≈5 nm) barrier were grown heteroepitaxially onto LaAlO _3 substrates by applying pulsed liquid injection metalorganic chemical vapour deposition technique. We report anomalous interface resistance increase with cooling just below superconductive transition temperature (T_c≅85 K) and enhanced suppression of supercurrent of strip-like YBa_2Cu_3O_7 film due to spin-polarized carriers injected from the ferromagnetic manganite layer.
Acta Physica Polonica A
|
2005
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vol. 107
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issue 2
230-234
EN
Ultrafast photoresponse of dc-biased optically-thick YBa_2Cu_3O_{7-δ} microbridges at T
EN
Transformers represent one of the oldest and most mature elements in a power transmission and distribution network. The new superconducting transformers are smaller and lighter than conventional ones and they have lower power losses, too. Also, the new 2G superconducting tapes with high resistivity in the normal state allow to build transformers with high short-circuit strength. The short-circuit current limiting feature of the superconducting transformer, which is the most important benefit of replacing conventional windings by superconducting ones, provides protection and significantly reduces the wear and tear of circuit breakers and other substation power equipment. This paper describes the design and experimental investigations results of a model of a 1-phase, 8.8 kVA superconducting transformer with windings made of 2G HTS tape. A special regard is given to the ability of the device's superconducting winding to limit the short-circuit current, in particular its equivalent resistance in normal state at a temperature of 77 K (i.e. resistance of the resistive layers of the HTS tape just after transition to the non-superconducting state).
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Superconducting Devices for Power Engineering

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EN
The paper presents the current state of research on superconducting devices for the electrical power system, i.e. transformers, fault-current limiters, and energy storages. In particular, it describes scientific achievements of the Laboratory of Superconducting Technologies of Electrotechnical Institute. The development of distributed and renewable energy sources, as well as the increasing number of receivers with low power factor will rise interest in superconducting fault-current limiters and superconducting transformers rated below 1 MVA. Previous studies were focused on the largest power transformers and highest current superconducting fault-current limiters. ReBCO coated conductors allow to build efficient superconducting AC devices. Superconducting tape of a layered structure (second generation HTS tape) enables the construction of transformer rated up to a few MVA without the usage of parallel conductors. Relatively high resistance of the tape in normal state allows to build fault-current limiters and fault-current limiting transformers. Superconducting transformers and superconducting fault-current limiters can help to increase connected power of distribution stations and thereby accelerate development of renewable energy sources.
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