Dependence of space charge dynamics in LDPE on history of voltage application

Abstract

The space charge phenomenon in PE (polyethylene) particularly in LDPE (low density polyethylene) is being widely researched for more than two decades. Despite various theories proposed by researchers, the charge dynamics in general and charge packets in particular, inside the polymeric insulation are yet to be completely known. The authors have investigated the dependence of charge dynamics on electric field using PEA (pulsed electroacoustic) technique. The experiments were carried out at 25 ºC on 100 µm LDPE film samples under applied electric fields of 100-150 kV/mm. External current measurements were also performed under similar conditions. The analysis of charge profiles and external currents shows that apart from other factors, charge formation and polarity of charge also depend on history of electric field application.Interesting observations were made on the consequence of such results. Experiments were performed repeatedly on virgin samples, taken from same lot, and the results were found to be almost same. It is believed that the effect of history of voltage application on charge formation, presented in the paper, is useful for understanding practical behavior of LDPE which, if used in power cables, is expected to serve as a dielectric for several years -accumulating a lot of history of voltage application.

Dielectric and space charge characteristics of nano-modified liquid silicone rubber for high-voltage DC cable accessories

“…Cable accessories are an essential part of the high-voltage DC cable system, and its insulation safety and reliability affect the entire transmission network [6]. Electrode injection and impurity ionization cause the space charge to easily accumulate inside the polymer insulation, which in turn causes local field strength distortion, insulation material aging, partial discharge, and even insulation breakdown [7]. Studies have shown that the main reason for the frequent failure of DC cable lines is the insulation failure of the DC cable accessories [8], the essence of which is the accumulation of space charge of the insulating material [9][10][11].…”

Review of space charge measurement by pulsed electro-acoustic technique

“…The analysis of charge density measurement for composites were done based on the published results by the researchers [3,6,7,11]. Figure 6 shows the charge density results where red, green and blue, and orange line represents cross-linked polyethylene (XLPE), low density polyethylene (LLDPE) and polypropylene (PP) with different specimen thickness respectively.…”

“…When there is no internal charge in the sample, there will be no existence of space charge too in the sample. It just only the induced charge that is generated on the electrode reported by Du, Xu and Li [5], Chahal and Reddy [6] and Wei et al [7]. Figure 1 shows an example of profile obtained by PEA where red, blue and green line represent the charge density, electric field and potential [43] respectively.…”

“…Also, the morphologies of crystalline and amorphous regions relate to space charge behaviur [5]. Undoubtedly, various issues such as the type of electrode, applied field and temperature may affect the space charge accumulation in polymers [6]. In a like manner, researcher also explored [7] the space charge in different works such as measurement of the breakdown voltage using the PEA technique.…”

“…In a like manner, researcher also explored [7] the space charge in different works such as measurement of the breakdown voltage using the PEA technique. So, method that based on PEA technique [1][2][3][4][5][6][7] was used to measure, describe and testing space charge profiles. Further, there are several review papers concentrating on an acoustic over a decade.…”