Effect of Material Properties on High Frequency Signal Propagation and Partial Discharge Detection in Solid Dielectric Shielded Power Cables

High frequency signal propagation characteristics of shielded power cables, including attenuation, electromagnetic propagation velocity, and characteristic impedance, are determined mainly by the dielectric properties of cable insulation and semiconductive shields, as well as the metallic sheath structure. High frequency attenuation in two transmission class XLPE cables with differing ground structures is studied by computation and measurement. High frequency signal propagation in tape shield power cables is related to the conduction of the tape laps as the corrosion thereof forces sheath current to spiral down the tape. Computations and measurements have been conducted to study high frequency signal propagation characteristics in such cable as a function of fraction of spiraling sheath current and cable material properties. ^ Optimization of partial discharge (PD) detection technology based on historical evolution of key technologies is investigated with the conclusion that a fully digital is presently practical for a bandwidth in the range of 20 MHz which will increase to 100 MHz within a few years. ^ Three dimensional finite element analysis is applied to calculate PD magnitude as a function of discharge characteristics in a complex object, in this case, a separable connector. The PD magnitude is estimated from the product of the change of capacitance when discharge occurs and the partial discharge extinction voltage (PDEV). The calculated PD magnitude is compared with measurements for a controlled defect in a separable connector.