Differences in Characteristics of Long-Gap Lightning Impulse Breakdown between Vegetable and Mineral Insulating Oil
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Transactions on Electrical and Electronic Materials https://doi.org/10.1007/s42341-020-00238-4
REGULAR PAPER
Differences in Characteristics of Long‑Gap Lightning Impulse Breakdown between Vegetable and Mineral Insulating Oil Wenxiong Mo1 · Haoyong Song1 · Qingdan Huang1 · Yuqing Chen1 · Wei Wang1 Received: 22 April 2020 / Revised: 8 August 2020 / Accepted: 17 August 2020 © The Korean Institute of Electrical and Electronic Material Engineers 2020
Abstract Vegetable insulating oils, with higher fire point, lower biological hazard and better availability compared to traditional mineral insulating oils, have enormous potential to become the substitute of the latter, given the trend of green development of the power equipment, for example, the transformers. However, the obviously different constitution of the vegetable oils makes the circumstance hard when considering their application on the insulation for actual transformers. One of the significant deficiencies of the vegetable oils in working condition is their insufficient lightning impulse endurance under partial high electric fields and large discharge gaps. In this article, three kinds of transformer insulating oils, rapeseed oil, FR3 and 25# mineral oil were chosen to investigate the performances of these insulation materials under long-gap lightning impulses with positive and negative polarity respectively. The variation rules of breakdown voltage and velocity with the gap length were obtained. And the difference of the lightning impulse voltage endurance between the vegetable and mineral insulating oils as well as its causes based on theories of streamer and ionization potential (IP) were analyzed, which led to the conclusion that the gap increase causes more threat to the positive lightning impulse breakdown of vegetable insulating oils, compared to its counterpart. Keywords Vegetable insulating oil · Lightning impulse breakdown voltage · Streamer mechanism · Ionization potential · Mineral insulating oil
1 Introduction Research on Liquid dielectric’s breakdown and discharge characteristic is meaningful in the design, operation and maintenance of related electrical equipment. Since 1990s, vegetable insulating oil, as potential substitute of mineral insulating oil used in oil-immersed transformers, gained wide concern [1]. A lot of works focusing on the breakdown characteristic and discharge process of vegetable insulating oil under DC, AC and impulse waves were conducted [2–5], indicating that short discharge duration can better eliminate the outside interference (i.e. impurities) on the breakdown and discharge process of insulating oil gaps. So the lightning impulse breakdown characteristics of mineral and vegetable insulating oils were studied extensively.
* Haoyong Song [email protected] 1
Electric Power Test & Research Institute, Guangzhou Power Supply Co., Ltd., Guangzhou 510410, China
Based on the need of practical application on engineering, currently many researches about vegetable insulating oil’s breakdown and discharge properties unde
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