Leszek Jaroszynski

Analysis of Alternating Overcurrent Response of 2G HTS Tape for SFCL

The scope of this article was to find the transient response of the 2G high-temperature superconducting (HTS) tape under alternating overcurrent. The authors performed a series of measurements for the SF12050 HTS tape produced by SuperPower Inc. The tape was fed by a 50-Hz ac voltage source with adjustable amplitude. The temporal dependences of the tape current and voltage drops in each test segment were recorded simultaneously. The measurements were performed for the current amplitudes exceeding the critical value specified by the manufacturer ( Ic = 270 A @77 K, self-field). The instantaneous values of the tape temperature during overcurrent transient period were also determined. Additionally, the numerical analysis of the SF12050 tape was performed. A numerical model was built using PSPICE environment. The model assumes the nonlinear dependence of tape parameters in the function of temperature, as well as the variable cooling conditions during transient state. The constructed model was verified with measurement results.

Comparison of Overcurrent Responses of 2G HTS Tapes

In this paper, the comparison of transient responses of second-generation (2G) high-temperature superconducting (HTS) tapes under alternating overcurrent was presented. The authors performed the series of measurements of the SF4050 and SCS4050 HTS tapes produced by Superpower Co. The measurements were carried out for various amplitudes of current exceeding a critical value given by the manufacturer (Ic = 100 A, dc, @77 K, self-field). Seven measuring probes were soldered to each tape, which allow for simultaneous recording of the supplying current and voltage in each test segment. Tapes were immersed in liquid nitrogen bath under atmospheric pressure and supplied from the 50-Hz voltage source with adjustable amplitude. Numerical models of SF4050 and SCS4050 tapes were build using PSPICE environment. The models assume the nonlinear dependence of tape parameters in the function of temperature and the variable cooling conditions during transient state. The numerical results were compared with the measurements, and good correlation was achieved. Elaborated models allow for the calculation of the overcurrent responses of 2G HTS tapes with and without copper shunts.

Short-circuit current limitation by superconducting transformer

Limitation of thermal and dynamic effects of the passage of a short-circuit current can be obtained by limiting the short-circuit time and the value of the maximum initial short-circuit current - surge current. The paper presents the current state of research on superconducting transformers for the electrical power system, used for limiting the short-circuit current. The new 2G superconducting tapes with high resistivity in the normal state allow to build transformers with high short-circuit endurance. 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. Properly designed and built superconducting transformer reduces first peak of short-circuit current - surge current, in time shorter that 5 ms, what secures the transformer from dynamic and thermal failure.

Numerical model of the 10 kVA superconducting transformer

The paper proposes the circuit model of 10 kVA superconducting transformer implemented in PSpice. The model of second generation superconducting tape allow for the simulation of smooth transition of the yttrium superconducting layer into resistive state. Dependence between the electric field intensity and the current density is described by Rhyners power-law. A modified Jiles-Atherton equation has been used to describe the nonlinear magnetic core of the transformer. The current and voltage waveforms in the idle state, in the load condition and in the short-circuit of the superconducting transformer have been obtained. The waveforms have been compared with the results of the measurements to verify the computer model.

Overcurrent characteristics of second generation superconducting tape SF4050

Authors made measurements for the SF4050 high-TC superconductor coated tape produced by SuperPower Inc. The measurements were performed for the AC current amplitudes exceeding the critical value of this tape. The numerical model of the tape was build using PSpice environment. The model assumes the nonlinearities of tape parameters as the functions of temperature, as well as the variable cooling conditions during transient state. Simulation results were compared with measurement data. Streszczenie. Autorzy przeprowadzili pomiary dla taśmy SF4050 z warstwą nadprzewodnika wysokotemperaturowego produkowanej przez SuperPower Inc. Badania wykonano dla prądu zmiennego o amplitudach przekraczających wartość krytyczną prądu taśmy. Przy wykorzystaniu środowiska PSpice zbudowano model numeryczny uwzględniający nieliniowość parametrów taśmy i warunków chłodzenia. Wyniki symulacji porównano z danymi pomiarowymi. (Właściwości taśmy nadprzewodnikowej drugiej generacji SF4050 dla prądów powyżej wartości krytycznej).