Abstract
The article presents an extended computer model of a HTS (high temperature superconducting) 21 MVA 70/10.5 kV transformer with severalfold compound windings, based on a verified PSpice model of 10 kVA transformer with single windings. Two superconducting tapes: SCS12050 (with a copper stabiliser layer) and SF12050 (without a stabiliser) were used in the windings. The circuit model of the transformer developed in the PSpice environment considers Rhyner’s power law and the Jiles–Atherton description of the magnetic hysteresis loop. Two types of transient states were analysed: switching on a superconducting transformer to the network and an emergency short-circuit of the secondary winding. For the first five unidirectional current pulses generated when connecting an unloaded transformer to the network, the values of the pulse duration (γ angle), the temperature increase in the primary winding as well as the mean and effective values of the switch-on current were calculated. The waveforms of currents, voltages, changes in resistance and temperature during the operation short-circuit were compared for the windings with both types of HTS 2G (high temperature superconductor second generation) tapes. The conducted analysis allowed us to determine the influence of electrical and thermal parameters of the tapes in question on the effective limitation of current in transient states and the possibility of their use in the construction of superconducting transformer windings.
Highlights
Very thin HTS tapes are used in the construction of superconducting transformer windings, which means that the radial dimensions of the windings and the length of the magnetic core yoke are smaller than in a conventional transformer of the same power
The main advantage of superconducting transformers, is the possibility of limiting transient currents when connecting these transformers to the network and during emergency short-circuits in the secondary winding
Circuit modelling of a superconducting transformer was used in the PSpice programme to analyse the influence of electrical and thermal parameters of windings made of superconducting tapes (HTS 2G) on the waveforms of the instantaneous current, resistance, and temperature in transients in both the switching current and the short-circuit current
Summary
Very thin HTS (high temperature superconductor) tapes are used in the construction of superconducting transformer windings, which means that the radial dimensions of the windings and the length of the magnetic core yoke are smaller than in a conventional transformer of the same power. The literature on computer-based circuit modelling of the short-circuit current and switching on superconducting transformers in the PSpice environment and the analysis of the influence of the parameters of superconducting tapes on current limitation in transient states is relatively small. A significant calculation difficulty is the significant temperature non-linearity of resistivity and the variability of the critical parameters of the superconductor during the transformer connection to the network These factors make it difficult to design and manufacture a superconducting transformer with the required thermal and electrical parameters to effectively limit the switch-on current values. Circuit modelling of a superconducting transformer was used in the PSpice programme to analyse the influence of electrical and thermal parameters of windings made of superconducting tapes (HTS 2G) on the waveforms of the instantaneous current, resistance, and temperature in transients in both the switching current and the short-circuit current. At the end of the paper, future research aimed at improving the elaborated model is proposed
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