Evaluation of ester dielectric liquids for sustainable nanosecond pulsed power systems

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Williamson, Chris and Given, Martin J. and MacGregor, Scott J. (2025) Evaluation of ester dielectric liquids for sustainable nanosecond pulsed power systems. IEEE Transactions on Plasma Science. pp. 1-11. ISSN 1939-9375 (https://doi.org/10.1109/tps.2025.3639972)

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Abstract

The breakdown and degradation characteristics of ester-based dielectric liquids subjected to nanosecond impulses have been investigated and compared with those of conventional mineral oil. Experiments were performed using a ten-stage Marx generator delivering impulses across electrode configurations with varying field utilization factors. Two complementary studies were undertaken. First, a breakdown study was conducted, in which breakdown voltage, time to breakdown, and peak breakdown current were measured under both positive and negative polarities. Following this, a degradation study, where each liquid was subjected to 500 consecutive impulses prior to reevaluation under 25-kV ac partial discharge (PD) diagnostics, was undertaken. Results confirm the strong polarity dependence of nanosecond impulse breakdown, with higher breakdown voltages and longer time to breakdown observed under negative polarity. Ester liquids exhibited breakdown voltages comparable to mineral oil, but with consistently shorter delay times, indicating faster streamer initiation. In degradation tests, electrode conditioning produced apparent increases in breakdown voltage; however, PD measurements revealed that mineral oil experienced significantly greater deterioration, with larger increases in both peak and average PD. In contrast, both natural and synthetic esters showed more moderate degradation, with synthetic ester demonstrating the highest stability. The findings support the use of ester liquids as technically viable alternatives to mineral oil for pulsed power insulation applications.

ORCID iDs

Williamson, Chris ORCID logoORCID: https://orcid.org/0000-0003-1108-9402, Given, Martin J. ORCID logoORCID: https://orcid.org/0000-0002-6354-2486 and MacGregor, Scott J. ORCID logoORCID: https://orcid.org/0000-0002-8810-1716;
CORE (COnnecting REpositories)