Journal ArticleDOI
Modeling the polarization spectrum in composite oil/paper insulation systems
TLDR
A mathematical model of the polarization spectrum is proposed and it is shown that, from the derived model, some of the hidden RVM peaks can be identified.Abstract:
The determination of the polarization spectrum in the low frequency region of the dissipation factor, commonly has been used in practice to diagnose insulation conditions. The recovery voltage method (RVM) is one of the methods used to estimate the polarization spectrum. Nevertheless, current analysis of the RVM tests do not use all the information available from the test. In this paper, a mathematical model of the polarization spectrum is proposed. It is shown that, from the derived model, some of the hidden RVM peaks can be identified. Since the difficulty to derive a model from RVM data increases with the number of the peaks to be identified, a simpler model is always preferable. A scheme for determining the parameters of an equivalent circuit is also given, The composite oil/paper insulation is considered which is extensively used in cables and transformers. Cellulose paper, such as the Manila-Kraft type, which is used as insulation, exerts a major influence on the life of the equipment because of its hygroscopic nature. The importance of detecting and eliminating moisture from paper is crucial in oil-impregnated HV insulation. Analysis of the polarization spectrum has been used by several utilities to determine moisture in the paper. Recently, some test results indicated that the polarization spectrum may not clearly show important peaks corresponding to local moisture ingress and thus can mislead experts in the field, The developed model has been validated using RVM data of real power transformers.read more
Citations
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Journal ArticleDOI
Review of modern diagnostic techniques for assessing insulation condition in aged transformers
TL;DR: A description of commonly used chemical diagnostics techniques along with their interpretation schemes for transformer insulation condition assessment is presented.
Journal ArticleDOI
Deriving an equivalent circuit of transformers insulation for understanding the dielectric response measurements
TL;DR: In this article, a circuit model, which describes the dielectric behavior of the transformer's main insulation system, has been parameterized in order to identify the values of the parameters of the model and the correlation has been developed between the physical condition of the insulation and the equivalent model parameters that enable a clear and transparent interpretation of the test results.
Journal ArticleDOI
Investigations of Temperature Effects on the Dielectric Response Measurements of Transformer Oil-Paper Insulation System
TL;DR: In this paper, the effects of temperature on the dielectric measurements of a transformer under controlled laboratory conditions are investigated, and the results of practical on-site testing are also presented to demonstrate the possibility of errors that may be introduced in dielectrics test results analysis unless temperature effects are taken into consideration.
Journal ArticleDOI
Condition Monitoring of Power Transformers - Bibliography Survey
TL;DR: In this article, the authors proposed a preventive maintenance technique for power transformers, such as DGA, thermal monitoring, partial discharge measurement, capacitance and tan delta measurements, frequency response analysis, etc., to identify problems at an early stage before a catastrophic failure occurs.
Journal ArticleDOI
Review of time-domain polarization measurements for assessing insulation condition in aged transformers
TL;DR: A review of the time-domain polarization measurement techniques for the condition assessment of aged transformer insulation is presented in this article, where the polarization process is first described with appropriate dielectric response theories and then commonly used polarization methods are described with special emphasis on the most widely used return voltage (RV) measurement.
References
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Journal ArticleDOI
Status and trends in transformer monitoring
TL;DR: In this article, a survey of the most important methods for on-line monitoring and off-line diagnostics is given, and the area of life assessment is discussed, and in particular the difference between end-of-life of the insulating material and of the transformer is emphasized.
Book
Numerical Recipes Example Book
TL;DR: This is the revised and greatly expanded Second Edition of the hugely popular Numerical Recipes, with over 100 new routines (now well over 300 in all), plus upgraded versions of many of the original routines.
Journal ArticleDOI
Measuring and understanding the ageing of kraft insulating paper in power transformers
TL;DR: The aims of this paper are to present a limited review of techniques that are relatively new to the transformer monitoring field, to provide some recent results from this laboratory to demonstrate their potential application, and to show the need for a range of new tools if the ability to assess the condition of transformers and the remanent life of their insulation is to improve.
Journal ArticleDOI
The mysteries of multifactor ageing
V.K. Agarwal,H.M. Banford,B.S. Bernstein,E.L. Brancato,R.A. Fouracre,G.C. Montanari,J.L. Parpal,J.N. Seguin,D.M. Ryder,John Tanaka +9 more
TL;DR: In this paper, the authors have shown that the degree and rate of ageing of insulation depend on the physical and chemical properties of the material, the nature and duration of applied/induced stress(es), and material processing and treatment during manufacturing and subsequent use in equipment.
Journal ArticleDOI
Degradation of Insulating Materials of Transformers
TL;DR: In this article, a good correlation was found between the amount of gas generated from insulating papers in insulating oil and the retention of tensile strength and degree of polymerization.