Space charge effect and application in solid insulation dielectrics

Abstract

<p indent="0mm">Space charge effect and its application in solid insulation dielectrics are long-term issues with continuous development. The study of space charge effect is of great significance to high-voltage direct current (HVDC) transmission. This paper summarizes the development history and research progress of space charges in solid dielectrics, from the aspects of measurement technologies, damage, suppression, application, and simulation, etc. Currently, the most widely used space charge distribution measurement technologies can be roughly divided into two categories, acoustic effect technique and thermal effect technique, whose spatial resolution and application range are different. For the acoustic effect technique, pressure wave propagation method and pulsed electro-acoustic method are most commonly used with proven technique. The spatial resolutions of these two are similar, both can reach an average of <sc>10 μm.</sc> With extremely narrow pulses, the highest spatial resolution can reach about <sc>1 μm.</sc> The thermal effect techniques, such as thermal pulse method and laser intensity modulation method, have more advantages in spatial resolution and practicability, especially for micron-thick film detection. Future research may focus on the more widely application of space charge distribution measurement technologies to electrical equipment in operation. For the trap parameters and charge storage properties of insulation dielectrics, there is still a lack of reliable and practical measurement technologies. The results of the isothermal decay method are more reliable and credible, but the required measurement time is too long. Therefore, it has been rarely used in practice in recent years. The most commonly used methods, thermal stimulated discharge current method and photo stimulated discharge method, each has its own disadvantages. And their results for the same sample are quite different for mutual corroboration. In recent years, some researchers are more focused on piezo-stimulated current method, but this method is still in a preliminary stage of experiment and application. In general, the space charge effect has pros and cons. On one hand, space charge accumulation in solid insulation dielectrics may cause electric field distortion and discharge damage, eventually lead to breakdown and destruction of insulation. In order to prevent these damages, many effective methods have been proposed, such as surface modification of insulation dielectrics and material modification by additives. However, these methods have not yet been practically used in industrial applications. On the other hand, space charge effect also has many efficient applications. One of the most important applications is electret, a dielectric material that quasi-permanently stores real charges in surface or volume traps. A large number of significant contributions have been published on preparation process, charge characteristics and applications of electrets. The simulation research of space charges can mainly be divided into physical model research of space charge behavior and data processing of experimental results. The development of space charge simulation is relatively backward compared to other research fields as the physical model of space charge behavior has not yet been built completely. The issues of space charge effect and its application are involved with multiple factors. Although some technical and theoretical developments have been achieved in recent years, there are still some uncertain questions remained to be explored.