Study on the impact of space charge on the lifetime of pulsed capacitors

Compounding, Structure and Dielectric Properties of Silica-BOPP Nanocomposite Films

“…Such dielectric property improvements are highly desired for applications in metallized film capacitors and DC cables. For instance, space charge accumulation in conventional polymers under high DC electric field can degrade severely the insulation reliability and reduce lifetime of DC cable systems and film capacitors [7]- [9]. Considering that both cables and capacitors are critical components in HVDC transmission and distribution systems, as well as in voltage source converters (VSC) used for gridintefacing of renewables, increasing their life and/or reliability is of high interest.…”

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

“…The first stage most likely initiates the deterioration of the polymer film under the influence of electric field intensity during macromolecule ionisation due to electron tunnel transfer [88]. Direct degradation of dielectric film can be classified into two levels in accordance with electric stresses: the breakdown of low-density regions (PDs), which have an extremely aggressive interplay with the polymer surface, and the direct effect of electrons on the polymer layers near the electrode/dielectric interface (space charge) [89], [90].…”

“…Most polymer dielectric films utilised in capacitors are subjected to strong electrical fields, whether AC, DC or superimposed, that lead to space charge injection and accumulation in varying proportions in accordance with the applied field type [95]. Given that defects exist in polymer films, positive and negative charges be in an unequal state due to asymmetric atomic distribution in the defects, carriers will be attracted thus form charge traps [87], [89]. The space charge accumulation can lead to distortion of the local electric field in the dielectric [96].…”

“…The traps are classified as shallow and deep on the basis of activation energy [98]. Deep traps are formed in BOPP films when activation energy exceeds 1eV, whereas shallow traps are formed when activation energy is less than 1eV [89]. Polar groups, impurities, and catalysts are polarised under a low DC electric field to form a homocharge (symmetric polarity with the field) inside the dielectric.…”

“…While the heterocharge (asymmetric polarity with the field) forms inside the film as a result of injecting the charge under a higher electric field. The formation of heterocharge would strengthen the electric field near the electrode and reduces it in the middle of dielectric, which may reduce the breakdown voltage, unlike the effect of homocharge [89], [99].…”