Electrode influence on DC conductivity measurements of low density poly ethylene

Abstract

In high voltage DC applications one of the most critical parameters of insulation materials is the conductivity. It is however challenging to measure conductivity accurately, since it is influenced by composition, morphology, sample thickness, temperature, electric field strength and electrode material. There is no standard electrode material used for electrical characterization of insulation in research. It is known that different electrode materials give rise to different conduction currents and different space charge inside a polymer sample. It is also believed that oxide layers on metal electrodes influence the activation energy of the interface between the polymer sample and the metal electrode. In the present work, a pure nonstabilized LDPE was used to investigate different electrode materials. The following materials were investigated: brass, copper, aluminum, gold, silver and semi conductive polymer. The method of application of the electrodes onto the polymer samples was also varied. The results indicate that the contact material and the method how to connect the material to the polymer sample had an influence on the time behavior of the DC conductivity during 24h of polarization. It could be shown that the applied electrical field influenced the crystal structure of the sample.

Charging and Discharge Currents in Low-Density Polyethylene and its Nanocomposite

“…Later on the currents decayed much slower (the slope changed from −0.44 to −0.21 with the increasing electric field) indicating a gradually increasing dominance of the electrical conduction processes [13]. The steady state of the measured currents had not been achieved, which is commonly observed for LDPE, even during an extended measuring period of 17 days [15]. The knee point at~50 s manifests the transition from a polarization-dominated phase to a conduction mode.…”

“…It is worth mentioning that it is not uncommon that charging currents measured on different samples of the same material can be different and unavoidable uncertainties may arise due to slight variations in morphology, electrode-material interface, thickness inhomogeneity, etc. [14,15]. In this study, repeated measurements were conducted at each condition and typical and reproducible results were considered for further analyses.…”

Electrical Conductivity and Moisture Uptake Studies of Low Density Polyethylene Octylnanosilica Composite

“…Specifically, the conductivity of an insulator should stay low for long periods of time under electric field; this is important for many applications [1]. Experimentally, a strong dependence of electrode material on the conductivity suggests that the current is dominated by carriers injected from the electrodes [2,3]. A polymer composite is an inhomogeneous material and determination of its charge transport mechanisms is challenging [4].…”

Field-dependent electric conductivities of silicone rubbers deduced from measured currents and surface potential decay characteristics

“…[6] There are also other factors affecting the results of the measurements such as the strength of the applied electric field, temperature, conditions on electrode-material interfaces, etc. [7][8][9][10][11] The latter defines charges (and respectively currents) injected into the material during the measurements, which introduce uncertainties in the measured results (especially at high test voltages) and impose limits for the applied test field magnitude.…”