Abstract
The breakdown of polymer insulators at a nanosecond scale is a serious problem for high-voltage devices and pulsed power systems. This paper reviews recent developments in research on the mechanisms and characteristics of the breakdown of polymers at a nanosecond scale at the Northwest Institute of Nuclear Technology. An improved avalanche breakdown model is proposed, and a formula for the strength of the electric breakdown (EBD) is formulated based on it. The formative time lag of the avalanche breakdown model is then developed to verify it. Two research groups were formed to study the characteristics of the breakdown. One focused on the characteristics of single-pulse breakdown, such as the effects of size, polymer type, electrode, pulse width, and pulse polarity on EBD, with the aim of deriving expressions for EBD. The other research group examined cumulative (multi-pulse) characteristics of the breakdown with the aim of deriving a formula for the lifetime of the polymer. A method to design solid insulation structures is finally proposed.
Highlights
Polymer insulators are indispensable to high-voltage (HV) devices, especially for pulsed power systems,1–5 for insulating a pair of conductors from high voltages and separating different types of insulating dielectrics.6–13 As the output power of a pulsed power system increases,14–16 its volume decreases13–15,17 and lifetime increases, the breakdown of the insulator becomes a significant challenge.18–24 It is important to study the breakdown phenomenon of polymers at a nanosecond time scale because this can help engineers design optimum insulators
(2) Researchers have examined the characteristics of one-pulse breakdown of polymers to determine empirical and theoretical formulas for electric breakdown (EBD) based on factors such as thickness, polymer type, electrode, pulse width, and pulse polarity
The effect of polymer type on EBD86 is related to the polarization of dielectrics, which refers to the relative displacement of the negative and positive charges of atoms or molecules, the orientation of dipoles in the direction of the field, and the separation of mobile charge carriers at the interfaces of impurities or other defect boundaries caused by an external electric field
Summary
Polymer insulators are indispensable to high-voltage (HV) devices, especially for pulsed power systems, for insulating a pair of conductors from high voltages and separating different types of insulating dielectrics. As the output power of a pulsed power system increases, its volume decreases and lifetime increases, the breakdown of the insulator becomes a significant challenge. It is important to study the breakdown phenomenon of polymers at a nanosecond time scale because this can help engineers design optimum insulators. (2) Researchers have examined the characteristics of one-pulse breakdown of polymers to determine empirical and theoretical formulas for EBD based on factors such as thickness, polymer type, electrode, pulse width, and pulse polarity. (3) The characteristics of the multi-pulse breakdown of polymers ( called characteristics of cumulative breakdown) are investigated at a nanosecond time scale, and a theorybased formula for their lifetime is proposed for different conditions of application. Note that aside from research at the NINT, important developments have been reported by other organizations—for example, research on dielectric phenomena in solids at the University of Manitoba, summary of the electrical degradation and breakdown of polymers at the University of Leicester, analysis of the aging of polymers at the Xi’an Jiaotong University, model of charge injection in polymers at the University Toulouse III at CNRS, tree initiation mechanism at the Chinese Academy of Sciences, investigation into the effect of organic thickness at the University of Southampton, experiments to test the delay in solid dielectrics at the Faculty of Engineering, Ehime University, and new definitions of delays in the breakdown of polymers at the Siberian State University of Telecommunication and Informatics..
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