Abstract
Insulation condition is an essential aspect for the operational reliability of high voltage rotating machines in power plants and industrial applications. Insulation resistance (IR) and line-frequency dissipation-factor / power-factor (tanδ) measurement are often performed for the assessment of stator insulation condition. These measured values need to be normalized to a reference temperature (e.g. 40 °C) for comparison and trending and this is traditionally achieved by multiplying the results with a certain factor. However, this correction could be subject to error for an individual device since the correction factors recommended by various standards are average values of a certain number of machines at different conditions. In addition to that, insulation condition also has some influence on the temperature dependent property.With the introduction of Dielectric Frequency Response, DFR and Polarization/Depolarization Current, PDC as more advanced insulation diagnostic methods, with proper modelling, temperature correction can be done based on the insulation condition of an individual device and thus accuracy is considerably improved. In this paper, the background of DFR and its superiority in temperature correction are introduced. After that, the numerical Fourier and Inverse Fourier Transformation algorithm is applied to correct the time domain measurement (IR and PDC).
Highlights
High voltage motors and generators are key components in power generation stations as well as other applications such as oil & gas industry, steel company, pulp and paper industry
By following the proposed procedures given by this paper, more reliable temperature correction is possible for various insulation materials
Instead of using average values, the individual temperature correction, ITC algorithm is built on the basis of actual temperature behavior of the insulation material and takes its condition into account [6]
Summary
High voltage motors and generators are key components in power generation stations as well as other applications such as oil & gas industry, steel company, pulp and paper industry. Any unexpected failure of those high voltage rotating machines may cause extensive damage to other apparatus, long time interruption of power supply and significant financial losses. According to a CIGRE survey [1], stator insulation is the component that has the highest failure rate for hydrogenerators. Insulation resistance, IR (including the polarization index) and dissipation factor / power factor / tanδ test are the most widely used testing techniques all over the world. By following the proposed procedures given by this paper, more reliable temperature correction is possible for various insulation materials
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