Abstract
The surface charge and space charge accumulation in paper used in oil–paper insulation system may distort electric field distribution and lead to the flashover and breakdown of insulation system. In this paper, the effect of gas-phase fluorination on the surface charge and space charge characteristics of oil-impregnated Nomex paper was investigated. Nomex T410 was fluorinated at 25 °C using F2/N2 mixtures with 20% F2 in volume at 0.05 MPa for 15, 30 and 45 min. Fourier Transform Infrared Spectroscopy (FTIR) proved that the molecular chain scission and cleavage occurred during gas-phase fluorination. Furthermore, the surface charge and space charge characteristic of the original and fluorinated oil-impregnated paper were measured using an electrostatic voltmeter and Pulsed Electroacoustic (PEA) equipment respectively. Furthermore, the hole and electron trap distribution of the samples were obtained by Isothermal Surface Potential Decay (ISPD) model. The results showed that both the positive and negative charge decay rates were accelerated by gas-phase fluorination and the hole, electron trap energy and density of the fluorinated samples were reduced by fluorination. It is suggested that the space charge dissipation was also accelerated by fluorination, indicating that gas-phase fluorination is an effective approach to modify the charge dynamics of oil-impregnated Nomex paper.
Highlights
Nomex paper has been recognized as an excellent insulation material due to its good thermal stability, stable mechanical and electrical properties and has been widely used in dry-type, converter and oil immersed transformers among others, in which the reliability of the oil-paper insulation system greatly influences the safety of the power transmission system [1,2]
Previous researches indicate that the surface charge accumulated on the oil paper interface and the space charge accumulated in the oil impregnated paper may accelerate the degradation process of the oil paper insulation system, distort the electric field distribution and lead to insulation failures such as flashover and breakdown [3,4]
Previous studies show that the surface charge dissipation of oil-impregnated cellulose insulation paper under DC and pulse voltage could be accelerated by gas-phase fluorination [25]
Summary
Nomex paper has been recognized as an excellent insulation material due to its good thermal stability, stable mechanical and electrical properties and has been widely used in dry-type, converter and oil immersed transformers among others, in which the reliability of the oil-paper insulation system greatly influences the safety of the power transmission system [1,2]. Wang et al [8] and Huang et al [9] studied the influence of thermal aging and voltage reversal on the space charge characteristic of oil-impregnated paper insulation, respectively. Tang et al [16] and Liao et al [17] have synthesized nanoparticles modified insulation paper and investigated the influence of doped nanoparticles on the thermal and electrical properties of cellulose insulation paper. Previous studies show that the surface charge dissipation of oil-impregnated cellulose insulation paper under DC and pulse voltage could be accelerated by gas-phase fluorination [25]. The results showed that gas-phase fluorination could accelerate the surface charge and space charge dissipation of oil-impregnated Nomex paper
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
