Capacitance loss characteristics of metallized film capacitors under atmospheric corrosion

As the key components, metallized film capacitors (MFCs) are widely used in power system. Working at high temperature and humidity conditions, oxygen and moisture in atmosphere will permeate into MFCs and initiate electrode corrosion, which contributes to capacitance loss, and thus the reliability is reduced. In this work, a capacitance loss model for atmospheric corrosion is proposed to study the aging pattern of MFCs. Accordingly, an accelerated aging test with different temperature-humidity combinations is carried out to investigate the corrosion behavior at various temperature and humidity conditions. The results indicate the corrosion sites tend to distribute around the fibers on polymer films. The capacitance loss rate declines along time because of formation of oxide layers. It is also found temperature has a predominant effect on corrosion process in contrast of humidity.