Failure Characteristics and Mechanism of Nano-Modified Oil-Impregnated Paper Subjected to Repeated Impulse Voltage

Potao Sun; Wenxia Sima; Dingfei Zhang; Xiongwei Jiang; Huangjing Zhang; Ze Yin

doi:10.3390/nano8070504

Failure Characteristics and Mechanism of Nano-Modified Oil-Impregnated Paper Subjected to Repeated Impulse Voltage

Nanomaterials (Basel). 2018 Jul 7;8(7):504. doi: 10.3390/nano8070504.

Authors

Potao Sun^{1

2

3}, Wenxia Sima⁴, Dingfei Zhang⁵, Xiongwei Jiang⁶, Huangjing Zhang⁷, Ze Yin⁸

Affiliations

¹ State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Chongqing 400030, China. sunpotao@cqu.edu.cn.
² College of Engineering Materials, Chongqing University, Chongqing 400030, China. sunpotao@cqu.edu.cn.
³ Department of Electrical and Computer Engineering, University of Florida, Gainesville, FL 32611, USA. sunpotao@cqu.edu.cn.
⁴ State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Chongqing 400030, China. cqsmwx@cqu.edu.cn.
⁵ College of Engineering Materials, Chongqing University, Chongqing 400030, China. zhangdingfei@cqu.edu.cn.
⁶ State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Chongqing 400030, China. jiangxiongweicqu@163.com.
⁷ State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Chongqing 400030, China. Huangjing_Zhang@cqu.edu.cn.
⁸ State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Chongqing 400030, China. cquyinze@cqu.edu.cn.

Abstract

Nano-modification is a prospective method for improving the electrical properties of transformer oil. In most situations, transformer oil combined with cellulose paper is used to construct an insulation system for power equipment, such as power transformers. However, the influence of nanoparticles on the electrical performance of oil-impregnated paper is still unclear. Therefore, in this paper, we identify the failure characteristics of both fresh and nano-modified oil/paper. Specifically, the accumulative failure characteristics of nano-oil-impregnated paper (NOIP) are experimentally determined. The space charge distribution and trap characteristics of fresh paper and NOIP were measured, and the effect of nanoparticles on the space charge behavior are then analyzed. Finally, we measure the microstructure of fresh paper and NOIP subjected to repeated impulses. The test results indicate that nano-titanium oxide (TiO₂) particles have a limited effect on the breakdown voltage of NOIP. However, the particles can dramatically improve the resistant ability of NOIP against repeated impulses. For the NOIP with a nano-concentration of 0.25 g/L, the improvement reaches 62.5% compared with fresh paper. Under repeated applications of impulse voltages, the space charge density of NOIP is much lower than that of fresh paper. The deep trap density of NOIP is much higher than that of fresh OIP, whereas shallow trap density is relatively lower. Micropores are generated in paper insulation subjected to repeated impulses. The amount of the generated micropores in NOIP is lower than that in fresh paper. Nano-TiO₂ particles suppress the accumulation of space charge in the oil paper insulation, which weakens the electric field distortion in the dielectric. However, nanoparticles reduce the accumulative damage caused by repeated impulses. The above two points are considered the main reasons to improve the resistant ability against repeated impulses.

Keywords: accumulative effect; atomic force microscope; micropore structure; nano-oil-impregnated paper (NOIP); space charge.