A new method for assessment condition of oil-paper insulation based on the characteristics of frequency domain spectroscopy

It is important to assess the condition of the cellulose insulation in transformer. However, taking paper samples from a transformer is both impractical and destructive. In this paper, a new method for assessment ageing condition of oil impregnated insulation pressboard based on frequency domain spectroscopy (FDS) was proposed. The FDS measurements were taken on oil impregnated insulation pressboards with five ageing levels at moisture content of 1.22%, 2.06%, 3.02% and 3.87%. The dielectric loss of all the samples were calculated bytanδ (f)interpolationandthe ageing condition assessment database which contains data of five ageing levels and 1%-4% moisture content was built. It is found that thetanδ (f)interpolation is more sencentive to ageing and moisture. It could realize the ageing condition assessment by comparing thetanδ (f)interpolation curve with the curves in the database.The assessing result of the middle-low main insulation life of a 220kV transformer valided that it is effective and time saving to use the new method for ageing condition assessment.

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On: “Correction of topographic distortions in potential‐field data: A fast and accurate approach” by Jianghai Xia, Donald R. Sprowl, and Dana Adkins‐Heljeson (April 1993 GEOPHYSICS, p. 515–523).

Geophysics ◽

10.1190/1.1443404 ◽

1993 ◽

Vol 58 (12) ◽

pp. 1874-1874

Author(s):

David A. Chapin

Keyword(s):

Point Source ◽

Frequency Domain ◽

Potential Field ◽

Field Data ◽

New Method ◽

Potential Fields ◽

Potential Field Data ◽

Source Method ◽

Equivalent Point ◽

Breakthrough Technology

Xia et al. do an excellent job developing a new method for using the equivalent point source method in the frequency domain. The transformation from a varying datum to flat datum has always been a major problem in potential fields data. This is because the existing methods to perform this transformation have tended to be cumbersome, time‐consuming, and expensive. I congratulate the authors for this breakthrough technology.

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Aerodynamic Forces Approximations Calculated With a New Analytical Formulation

Volume 9: 6th FSI, AE and FIV and N Symposium ◽

10.1115/pvp2006-icpvt-11-93930 ◽

2006 ◽

Author(s):

Djallel Eddine Biskri ◽

Ruxandra Mihaela Botez

Keyword(s):

Least Squares ◽

Frequency Domain ◽

Approximation Method ◽

Unsteady Aerodynamics ◽

Analytical Form ◽

New Method ◽

Aerodynamic Forces ◽

Laplace Domain ◽

Analytical Formulation ◽

Multidisciplinary Study

Aeroservoelasticity is a multidisciplinary study of three main disciplines: unsteady aerodynamics, aeroelasticity and servo-controls. Two classical methods are used in the literature to approximate the unsteady generalized forces from the frequency domain Q (k) to the Laplace domain Q(s) and these methods are: the Least Squares LS and the Minimum State MS. In the present paper, we present a new method, called Corrected Minimum State (CMS), based on the Standard MS approximation method. This new CMS method uses an analytical form of the error as function of Laplace variable similar to the analytical form of the aerodynamic forces calculated with the MS method. We applied this new method to an F/A-18 aircraft and we found that the CMS method brings improvements in the approximation results in comparison with the standard MS method. It is shown that use of the CMS method on an F/A-18 aircraft will give better results in terms of convergence speeds and precision than the MS method.

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