Research on Delamination Damage of YBCO Tape Under DC Impact Based on Hilbert–Huang Transform

The short-circuit fault current on the dc side affects the operation safety of the multiterminal flexible HVdc transmission system seriously. The resistance-type superconducting fault current limiter (RSFCL) has received extensive attention in limiting the dc impact current because it has fast response speed and zero impedance at steady state. YBCO tapes are susceptible to delamination damage under large dc impact and it will affect the operation of RSFCLs. However, the existing methods of distinguishing the delamination damage of YBCO tape need an extra observation or testing after dc impact. These methods cannot meet the requirements for monitoring and protection when RSFCLs coming into use in the power system. In this article, the Hilbert-Huang transform (HHT) is used to analyze the delamination damage of YBCO tapes under dc impact to avoid extra observation and testing. The dc impact test on the YBCO tape sample is carried out and the test data are obtained. HHT is applied on the joule thermal power waves (TPWs) of the YBCO tape samples obtained from the dc impact test as the input signal. Hilbert spectrums and instantaneous energy spectrums (IEs) of the TPW signals are calculated and the difference between IEs of TPW signals of intact samples and delaminated samples is shown and explained. The feasibility of IEs of TPW signals can be as a monitoring target to avoid the stratification damage of YBCO tapes. The proposed method may aid in the on-load monitoring on RSFCLs and provided a new tack for related research.