Oil Impregnated Pressboard Barrier Systems Based on Ester Fluids for an Application in HVDC Insulation Systems

Abstract

Abstract:Ester-based insulation fluids are being increasingly used in high-voltage insulation systems. The reasons are the advantages in the area of ecological compatibility and resource-saving provision. The intention to use ester-based insulation fluids in high voltage direct current (HVDC) equipment is new. The major challenge in designing the HVDC insulation system is, that the systems do not only experience an alternating voltage, but also a direct voltage Offset. This presents a challenge to predict the electric field distribution. For this purpose, basic investigations are carried out in the form of conductivity investigations for various insulation barrier systems. In addition, a mineral oil serves as a reference oil for estimating existing insights. The results show the influence of the ester-based insulating liquids on the direct current (DC) conductivity for basic arrangements, consisting of pressboard barriers and mixed insulations.

A Novel Oil-Immersed Medium Frequency Transformer for Offshore HVDC Wind Farms

“…The results of the second series of ester OIP measurements together with the results of the first series of ester OIP measurements (with using Arrhenius results for 30 °C) can be preliminary used for the insulation design of an HVDC ester MFT prototype. Limited information about the conductivity of biodegradable ester oil under HVDC stress is accessible [61,104] and in case of ester OIP there is even less information available [62]. Figure 3-18 demonstrates comparisons between the measurement results of this work with the measurements presented in literature.…”

“…As preliminary measurements showed an unstable and varying results for the polarisation current of ester oil, to get stable current curves it is decided that a conditioning is to be performed on the ester oil and the polarization time to be increased from 1h (as was the case for mineral oil) to 3h for the ester oil. To reach repeatable results it is also decided to perform a set of conditioning stress applications before each measurement [62]. In case of ester OIP it is performed like the measuring method for mineral OIP and a 3 hours measurement is performed.…”

Green Solution for Insulation System of a Medium Frequency High Voltage Transformer for an Offshore Wind Farm

“…However, the electrical conductivity values given in the literature are typically obtained at low test voltages and therefore, are hardly applicable for designing an HVDC insulation [12]. Information regarding conductivity of biodegradable synthetic ester oil under HVDC stress is rather limited [13,14] and even less data is available for ester OIP [15].…”

“…As the preliminary tests showed unstable results for the polarization current of ester oil, it was thus decided to perform conditioning for the ester oil and to increase polarization time from 1 h (which was used for mineral oil) to 3 h [15]. Ester OIP is tested similarly to the mineral OIP for 3 h. Tables 1 and 2 summarize the conductivity measurements results for ester and mineral oils/OIPs whereas Figure 5 presents them graphically.…”

“…Energies 2022, 15,1998 Acknowledgments: Funding from the Swedish Energy Agency and financial support Rise Research Institutes of Sweden is gratefully acknowledged, as are helpful research assistance from Morteza Eslamian and Oriol Guillén Sentís and conductivity measurements assistance from Joakim Rastamo and Marcus Svensson. Any remaining errors reside solely with the authors.…”