Research On The Effects Of Pressure In The Dielectrometry Measurements Of Moisture Content In Pressboard

The contacting state and contacting pressure between the pressboard and the electrode of capacitive sensor can affect the measurement of moisture in transformer insulated pressboard. The affection of pressure that put on the pressboard in the test of moisture measurement is presented.The thesis introduces the complex permittivity and its disturbance factors. With three models, the effective dielectric constant of pressboard can be calculated. When the pressboard is compressed, the complex permittivity should also changes.The measurement system of moisture content in pressboard concludes sinusoidal signal generator, capacitive sensor measuring moisture content and interface circuit. For the dielectrometry sensor can be presented by a lumped element circuit, the complex permittivity of pressboard can be calculated.Results are presented of measurements, of the effects of compressive stress on the gain and phase of output voltage. For the results of measurement also depend on the compression of drive electrode. A new lumped element circuit is presented, which can be perfectly explain the differences.By means of the finite element analysis software ANSYS9.0, the circuit analysis is made. The result curves indicate that the changes of the capacitance and conductance should affect the output voltage together. This thesis finally provides a method to analyze the compression value of pressboard and electrode using ANSYS9.0, which may provides mode extraction results for next research and tests.