This letter proposes improved time-frequency maps for separating multiple partial discharge (PD) sources in cable terminations. PD signals are acquired through a digital measurement system and a high frequency current transformer. The waveform of each pulse is analyzed by synchrosqueezed wavelet transform, and six representative feature parameters are proposed to form time–frequency maps. The results show that the proposed algorithm is effective for discriminating mixed PD sources in cable terminations and pulses from power electronic devices detected simultaneously by the PD measurement system.

Although understanding the wetting behavior of solid surfaces is crucial for numerous engineering applications, the mechanisms driving the motion of Wenzel drops on rough surfaces remain incompletely clarified. In this study, the contact angle and contact angle hysteresis of Wenzel drops on superhydrophobic surfaces are investigated from a thermodynamic perspective. The free energy of the system is theoretically analyzed, thereby determining the equilibrium contact angle. Based on the sessile drop method, the relationship between the free energy barrier and the drop volume is calculated quantitatively, enabling the determination of advancing and receding contact angles under zero free energy barrier conditions. The theoretical calculations agree well with the experimental data. These findings enhance the understanding of the interfacial interactions between Wenzel drops and superhydrophobic surfaces.