Ageing: Causes and Effects on the Reliability of Polypropylene Film Used for HVDC Capacitor

Haider M. Umran,Yushuang He,Feipeng Wang

doi:10.1109/access.2020.2976526

Haider M. Umran, Yushuang He + Show 1 more

Open Access

https://doi.org/10.1109/access.2020.2976526

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Abstract

It is well-known that the high-performance polymeric dielectric films used for high-voltage DC capacitors should have outstanding capabilities in terms of electrical and mechanical properties in order to face harsh operating conditions. Many factors limit the ability of these thin films to face different and growing stresses according to modern electrical requirements. Microstructure properties, additives, impurities, defects formed during manufacturing as well as applied stress types significantly affect the performance of dielectric films and their operational lifetime. This paper presents a comprehensive review of the factors which affect the ageing, degradation and breakdown of metallised polypropylene (PP) capacitors films. The effects of microstructure, surface morphological properties, mechanical properties and defects on the reliability of biaxially oriented polypropylene films (BOPP) are studied. In addition, the phenomena affecting dielectric performance and ageing mechanisms which are induced by electrical, thermal and electrothermal stresses are discussed.

Highlights

The increasing penetration of renewable energy systems and the urgent need for their reliable integration with power transmission systems that operate under diverse conditions have become major challenges
The performance of dielectric films can be efficiently improved by enhancing their ability to withstand DC high voltage levels, temperatures, pulse, and superimposed voltages and harsh working conditions
The key points that affect the performance, ageing and development films of metallised polypropylene (MPP) capacitors and that require emphasis are summarised as follows: 1. The crystallinity and defects of the biaxially oriented polypropylene films (BOPP) film play a substantial role in determining the electric field threshold, space charge formation, leakage current, and partial discharge (PD) events, which are the main factors during the ageing of BOPP films

Summary

INTRODUCTION

The increasing penetration of renewable energy systems and the urgent need for their reliable integration with power transmission systems that operate under diverse conditions have become major challenges. The space charge accumulation can lead to distortion of the local electric field in the dielectric [96] This process generates electromechanical stresses that lead to the deformation of the molecular chains of the material, initially resulting in property deterioration and accelerating dielectric material ageing [63], [97]. PD is attributed to local breakdowns that do not damage the dielectric structure when the local electric field strength exceeds the breakdown resistance of the material (low-density breakdown regions) This process results in the gradual localisation of high temperatures and increases pressure [14], [118]. Corrosion with ripple current causes the dielectric strength to deteriorate and represents a potential failure mechanism [132], [133]

BREAKDOWN MECHANISMS

CONCLUSION