Open AccessEffects of ambient humidity and thermal aging on properties of Nomex insulation in mining dry‐type transformer
Author(s) -
Li Lu,
Song Jiancheng,
Lei Zhipeng,
Kang Ailiang,
Wang Zhengyu,
Men Rujia,
Ma Yun
Publication year - 2021
Publication title -
high voltage
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.732
H-Index - 20
ISSN - 2397-7264
DOI - 10.1049/hve.2019.0293
Subject(s) - composite material , relative humidity , humidity , materials science , moisture , water content , corona discharge , accelerated aging , thermal decomposition , analytical chemistry (journal) , chemistry , meteorology , geotechnical engineering , environmental chemistry , electrode , physics , organic chemistry , engineering
Abstract Temperature and humidity are the main factors that cause the decomposition of Nomex paper widely used as turn‐to‐turn insulation material of mining dry‐type transformers. In this study, for understanding the effect of ambient humidity and thermal aging on the properties of Nomex paper, specimens with the initial moisture content of 7% were aged in the oven for 168, 504, 672 h at 180°C, respectively. After thermal aging, corona discharge experiments of unaged and aged specimens with different aging degrees were carried out at different relative humidity (RH) levels from 10 to 70%. The characteristic parameters of corona discharge, such as the average discharge amplitude and the number of discharges, were measured. Then, the surface conductivity and the surface potential decay rate were measured. The morphology and attenuated total internal reflectance Fourier transform infrared spectroscopy were also analysed for explaining the difference of properties between unaged and aged specimens. The experiment results indicate that the average discharge amplitude decreases with the increase of RH or the deepening of the aging degree of specimens, but the number of discharges shows the reversal tendency. The changes in the physical structure and chemical composition, which is induced by the hydrolysis reaction of Nomex paper, accelerate the surface potential decay and increase the surface conductivity.