AC Loss Analysis in Superconducting Cables Carrying Characteristic and Noncharacteristic Harmonic Currents

Harmonic distortions—especially in current wave

form—are the inherent nature of any power system, such as urban grids, wind farms, electric aircraft, and other electrified transportation units, that could change the ac loss value in high-temperature superconducting (HTS) cables. The aim is to investigate the impact of nonsinusoidal currents with different integer harmonics, interharmonics, and subharmonics on the ac loss characteristics of a 22.9 kV, 50 MVA HTS cable. This was accomplished by using an equivalent circuit model (ECM). To do so, current waveforms containing different harmonic components were passed to the ECM of HTS cable. For evaluating the impact of distorted current waveforms on the ac loss of the HTS cable, the ECM was validated by means of finite-element method (FEM) in tape level. The results of validation phase have shown good agreement between the ac loss value derived by ECM and those calculated by FEM published in the literature. The results showed that when current waveform was distorted by harmonics, the value of ac loss was changed significantly with respect to the variations of harmonic phase angle, order, and amplitude. Results also indicated that fifth harmonic order has the highest impact on the ac loss value and could increase 6%–80% of ac loss in comparison to pure sinusoidal current. Subharmonics and interharmonics could also increase the ac loss value to maximum 88% and 64% higher than that of sinusoidal condition.