油纸绝缘水分平衡样品的制备及水分评估频域特征量提取

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Abstract In order to promote the applicaton of the frequency-domain dielectric spectroscopy (FDS) to the nondestructive diagnosis of oil-paper insulation states of transformer, it is necessary to establish a reliable dielectric response database of oil-paper insulation with different equilibrium moisture contents in the laboratory. In this paper, a new preparation method for oil-paper insulation samples with different equilibrium moisture contents is proposed and the transient and stable frequency domain dielectric responses of oil-paper insulation during the migration process of moisture between oil and pressboard are deeply investigated. In the meanwhile, the quantitative relationships between moisture and characteristic parameters extracted from frequency domain dielectric properties are established. Finally, the actual moisture content of pressboards is measured by the Karl Fischer moisture meter to verify the validity of the proposed preparation method. Results show that in the migration process of moisture between oil and pressboard, the real part C′ of the complex capacitance increase obviously within 10^-3~10⁰Hz, while the imaginary part C″ of the complex capacitance and the dielectric loss parameter tanδ present a clear tendency towards the high frequency region. The clear functional relationships between tanδ, C′, C″ and the moisture content in the pressboard are respectively observed in their characteristic frequency points(f=10^-3Hz, 10^-2Hz, 10^-1Hz, 10⁰Hz). The sample preparation method proposed in this paper can be used to accurately manufacture the pressboards with expected equilibrium moisture contents.

Key words： Frequency dielectric response oil-paper insulation moisture equilibrium dielectric loss factor characteristic frequency

Received: 08 September 2013 Published: 20 October 2015

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