Space charge characterization in biaxially oriented polypropylene films

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

“…With the increase of the applied voltage influence, the majority of positive charges are overlapped or re-combined with the negative charge during the mutual migration of the injected charge. Ultimately, the high-density heterocharge accumulated adjacent to the anode due to the continuous migrations of numerous negative charges injected [105]. The behavior and effect of the space charge vary in accordance with the type of voltage applied to the dielectric film, as explained by the following.…”

“…The working principle of these methods depends on the displacement of space charge within dielectric by disturbance to generate a displacement current measured by an external circuit [105]. The spatial resolution of conventional mechanical or electrical pulse disturbance-based methods is around several micrometers which causes them unsuited for the space charge measuring of thin films of capacitorgrade.…”

“…The negative charge creates in the deeper bulk of film due to the migration of space charge injected under the effect of high voltage [105]. Where the density and level of the charge trap partially determine the speed of space charge migration within the film.…”

“…The maximum level of the applied DC electrical field distortion on BOPP film due to charge accumulation is 80%. Thus, the accumulated space charge would enhance the ability of PD to cause energy losses and electrical ageing accumulation; as such, the capacitor dielectric lifetime is shortened [89], [105], [111]. The life of the capacitor dielectric decreases by 2% with each 8 • C increment over the temperature range of 40 to 65 • C [112].…”

“…The space charge is highly dependent on frequency: The charge moves deep into the bulk of the sample at a low frequency, whereas the amount of trapped charges increases as frequency decreases [113]. Thus, the amount of the space charge injected under AC voltage is considerably smaller than that stored in the same dielectric under DC voltage with the same root mean square value as the AC voltage [89], [105]. The breakdown under DC stress begins near the bulk of the dielectric, whereas that under AC stress begins near the sample-electrode interface.…”