Dielectric Properties of Electrical Insulating Liquids for High Voltage Electric Devices in a Time-Varying Electric Field

The motivation to improve components in electric power equipment brings new proposals from world-renowned scientists to strengthen them in operation. An essential part of every electric power equipment is its insulation system, which must have the best possible parameters. The current problem with mineral oil replacement is investigating and testing other alternative electrical insulating liquids. In this paper, we present a comparison of mineral and hydrocarbon oil (liquefied gas) in terms of conductivity and relaxation mechanisms in the complex plane of the Cole-Cole diagram and dielectric losses. We perform the comparison using the method of dielectric relaxation spectroscopy in the frequency domain at different intensities of the time-varying electric field 0.5 kV/m, 5 kV/m, and 50 kV/m. With the increasing intensity of the time-varying electric field, there is a better approximation of the Debye behavior in all captured polarization processes of the investigated oils. By comparing the distribution of relaxation times, mineral oil shows closer characteristics to Debye relaxation. From the point of view of dielectric losses at the main frequency, hydrocarbon oil achieves better dielectric properties at all applied intensities of the time-varying electric field, which is very important for practical use.

Moisture effects on AC dielectric strength and partial discharge inception voltage in natural monoesters

It is essential to analyse the dielectric performance in a humid environment of insulating liquids of plant origin, considered as alternatives to mineral oil (MO) which is not environmentally friendly. This paper focuses on the effects of different moisture levels on the dielectric strength and partial discharge initiation voltage of two natural monoesters, based on castor oil (CO) and palm kernel oil (PKO), and MO. The different samples were moistened with a glycerol solution, then sealed and stored for 12 days to allow further diffusion of moisture into the samples. Dielectric strength was statistically evaluated from IEC 60156. Partial discharge inception voltage (PDIV) experiment was performed in conformity with a modified IEC 61294 purpose at ambient temperature. Based on the experimental observations, the moisture has different behavior on dielectric strength and PDIV of insulating oils. Monoesters have a better withstand to water contamination than MOs in power transformers.

Fullers Earth Treatment for Esters Liquids used in Power Apparatuses: Inferences and Arguments

Insulating Liquids are widely used for their electrical and thermal properties in power apparatuses, particularly at the level of liquid-filled transformers. With the shift in engineering aspects towards sustainable development, it is important to find a sustainable solution with ecofriendly nature. Therefore, alternative (biodegradable) liquids are of high importance in the global transformer communities. In the present study, the alternative dielectric fluids (ester-based) feasibility for potential regeneration with Fuller’s earth is investigated. The experimental results are confined to the reclamation temperature as well as the ratio of Fuller's earth (the sorbent) and the liquid. A suitable laboratory treatment apparatus is designed and is adopted in this study. Promising measurements to comment on the effectiveness of the treatment have been performed at controlled treatment temperature and sorbent-liquid ratio with the ASTM 7150-13 as a reference norm.The results of this study allowed 80°C and 1 g/30 ml as affirmative conditions for the present experimental conditions. Diagnostic measurements include turbidity, particle counter, and UV spectrophotometry before and after treatments. It is inferred that fuller’s earth is not a promising sorbent for the reclamation of ester liquids.