Insulation Delamination Detection of Three-Phase Composite Structure Based on Terahertz Time-Domain Spectral

The three-phase composite structure is widely used in the power industry, especially for insulation systems of power equipment. As delamination defects always take place on such equipment, i.e. defects occur inside the three-phase composite structure. Therefore, this paper proposes to used the terahertz time-domain spectroscopy (THz-TDS) to detect the inner defects of the three-phase composite structure. Firstly, a three-layer reflection model of the terahertz wave is established, and a corresponding theoretical analysis of three-phase composite with insulation delamination defect is carried out. After then, an artificial sample with a delamination defect is prepared according to the actual structure of the three-phase composite. Besides, the THz-TDS analysis of the samples is carried out after tested by the THz-TDS system with the reflective mode. The experimental results show that the insulation delamination of the three-phase composite can be effectively identified by collecting the signals of the THz-TDS system. This paper theoretically and experimentally proves the feasibility of the new method based on the THz-TDS system for three-phase composite delamination nondestructive testing, which provides a new idea for inner defects detection within the three-phase composite and its condition assessment.