The electric field distortion due to space charge accumulations plays a significant role in the ageing, degradation and breakdown in failure of HVDC power cables. Currently, limited experimental results of the electric field dominated by space charges are insufficient to diagnose the power cables. This paper proposes an improved long short‐term memory network (LSTM) model for predicting the fluctuating maximum electric field (Emax) in cross‐linked polyethylene (XLPE) cable insulation. The various Emax data derived from the complex space charge behaviours were measured using the pulsed electroacoustic method. The model uses regularisation and dropout feedback in the LSTM unit, reducing the phenomenon of over‐fitting due to the limited data. It enhances the prediction accuracy and ability of long time prediction by improving the prediction of Emax with the non‐linear fluctuation. The predicted Emax approaches 190 kV/mm under 150 kV/mm and 60°C after 2 h. The predicted large variation in Emax under 120 kV/mm and 20°C after 4 h ranges from 130 to 160 kV/mm. It indicates high electric stress in the cable insulation during continuous operation. The proposed LSTM model is of great importance to guide the diagnosis of cable degradation in HVDC power cables.

Interfaces are essential components in polymer contact systems, which widely exist in electronic devices and power equipment. Interface charge originating from the mismatch of the electronic structure in interfaces is one of the key issues to modify the device performance due to its multifunctional migration and accumulation behaviors. Hence, the detection and analysis of the interface charge characteristics are of great importance to deeply understand the polymer contact system in various devices. This paper presents an overview of recent research progress in the interface charge properties at dielectric interfaces. Based on the theoretical analysis of the MWS polarization and electronic localized states, two typical approaches of discussing the interface charges from micrometer to millimeter are mainly studied. Acoustic method is prevalent in detecting the space charge in various dielectrics. However, owing to its limited resolution (several µm), it is difficult to clarify the charge distributions at the interface with a micro‐scale. Probe microscopy presents a promising technique due to its flexible surface potential detection at a submicron scale. The challenges and prospects of acoustic and probe microscopy methods are discussed in this paper. The advanced techniques of interface charges can promote the development of new energy electronic devices.