scholarly journals Transformer lifetime management by analyzing the content of furan and gas dissolved in oil

2019 ◽  
Vol 112 ◽  
pp. 04004
Author(s):  
Irina Alina Chera Anghel ◽  
Elena Gatman
Keyword(s):  
Carbon Oxide ◽  
Technical Condition ◽  
Degree Of Polymerization ◽  
Gas Analysis ◽  
Insulating Oil ◽  
Invasive Test ◽  
Paper Insulation ◽  
Transformer Insulation ◽  
Cellulose Insulation

In order to see the transformer insulation status, the temperature profile, the degree of polymerization (DP), the furan compound content, the carbon dioxide, and carbon monoxide concentration are monitored. By evaluating the degree of polymerization (DP) of the cellulose paper insulation and furans in the determination of the insulating oil, it can estimate the lifetime of the transformer. Analysis of cellulose insulation paper to see the degree of polymerization (DP) can be performed safely only when the transformer is interrupted. However, being a non-invasive test, determination of furane content in an oil-insulating oil is often used as an alternative method for measuring the DP average of insulation paper. In order to analyze the technical condition of a transformer, furan content in oil should be used and interpreted as a primary chemical indicator in conjunction with the results of carbon oxide from the dissolved gas analysis, the acidity and moisture results from the chemical tests, the methanol content from the chromatographic tests and other monitoring techniques.

scholarly journals Determination of Transformers’ Insulating Paper State Based on Classification Techniques

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 427 ◽  
Author(s):  
Sherif S. M. Ghoneim
Keyword(s):  
Prediction Model ◽  
Power Flow ◽  
Degree Of Polymerization ◽  
Classification Techniques ◽  
Aging Rate ◽  
Insulating Oil ◽  
Insulating Paper ◽  
Key Indicator ◽  
Carbon Dioxide Co2

The continuity of transformer operation is very necessary for utilities to maintain a continuity of power flow in networks and achieve a desired revenue. Most failures in a transformer are due to the degradation of the insulating system, which consists of insulating oil and paper. The degree of polymerization (DP) is a key detector of insulating paper state. Most research in the literature has computed the DP as a function of furan compounds, especially 2-furfuraldehyde (2-FAL). In this research, a prediction model was constructed based on some of most periodical tests that were conducted on transformer insulating oil, which were used as predictors of the insulating paper state. The tests evaluated carbon monoxide (CO), carbon dioxide (CO2), breakdown voltage (VBD), interfacial tension (IF), acidity (ACY), moisture (M), oil color (OC), and 2-furfuraldehyde (2-FAL). The DP, which was used as the key indicator for the paper state, was categorized into five classes labeled 1, 2, 3, 4, and 5 to express the insulating paper normal aging rate, accelerating aging rate, excessive aging danger zone, high risk of failure, and the end of expected life, respectively. The classification techniques were applied to the collected data samples to construct a prediction model for the insulating paper state, and the results revealed that the fine tree was the best classifier of the data samples, with a 96.2% prediction accuracy.

Examination of State of the Cable Insulation by the Return Voltage

2018 ◽  
Vol 19 (6) ◽  
Author(s):  
Dmitry Semenov ◽  
Anna Sidorova ◽  
Pavel Romanov ◽  
Aleksey Kuvshinov
Keyword(s):  
Residual Life ◽  
Technical Condition ◽  
Actual State ◽  
Power Cables ◽  
Insulation Resistance ◽  
Cable Lines ◽  
P Factor ◽  
Paper Insulation ◽  
New System

Abstract The relevance of the study is conditioned by the need to determine the state and residual life duration of high-voltage cable lines to identify faulty and maintainable cables. The aim of the article is to determine a reliable scientifically grounded criterion for assessment of insulation characteristics of the cables in use and to perform a comparative analysis of the results obtained by the traditional method of diagnosing insulation with the results of a new method of assessment by the return voltage. In this regard, the article deals with the issues related to the testing of cables having oil-impregnated paper insulation, as well as with the issue of switching from planned replacement of cables to assessment of their actual state and period of residual life. The authors propose to use the method of examining the cables by the return voltage using the device for testing electrical insulation “UDEI-1” developed at the department of Electrification and Automation of the Nizhny Novgorod State University of Engineering and Economics. The article presents the results of measuring the return voltage of three cables that operated under different conditions. The cables had different technical state. The analysis of the estimation of the residual life of cables by the return voltage was carried out using such criteria as the PIRV polarization index, the LIRV electrical conductivity index, and the P-factor. The P-factor is the physical criterion demonstrating the aging of paper-oil insulation by the shape of the return voltage curve. It represents such characteristics of insulation aging as moistening. To compare the results of testing the cables by the return voltage with the conventional methods of diagnostics and to determine the actual technical condition of power cables, the authors applied the method of spatiotemporal reflectometry and the method of measuring insulation resistance with the determination of such indicators of state as insulation resistance normalized per one kilometer, absorption coefficient, and polarization index. The results of this article confirm that the return voltage gives a qualitative assessment of the state and degree of aging of cables with impregnated paper insulation. The authors proposed a new system for evaluation of cable condition by weighting coefficients. In this approach, the determination of residual life of cables with impregnated paper insulation is based on the values of the return voltage. Application of the new system gives opportunity to improve reliability of the power lines. Recommendations for the further operation of the studied cables are given. The materials of the article are of practical value for carrying out complex assessment of the technical condition of power cables by the return voltage and can be useful for drawing up a schedule for replacement or repair of cable lines depending on their actual state.

scholarly journals Terahertz Time Domain Spectroscopy of Transformer Insulation Paper after Thermal Aging Intervals

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2124 ◽  
Author(s):  
Liang Wang ◽  
Chao Tang ◽  
Shiping Zhu ◽  
Shengling Zhou
Keyword(s):  
Time Domain ◽  
Thermal Aging ◽  
Density Functional ◽  
Degree Of Polymerization ◽  
Transformer Oil ◽  
Optical Parameters ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Paper Insulation ◽  
Transformer Insulation

An accelerated thermal aging process was used to simulate the condition of paper insulation in transformer oil-paper systems. Optical parameters of the insulation paper after various aging intervals were analyzed with terahertz time-domain spectroscopy (THz-TDS) over the range 0.1~1.8 THz. The result shows that the paper had seven absorption peaks at 0.19, 0.49, 0.82, 1.19, 1.43, 1.53, and 1.74 THz, and density functional theory of B3LYP/6-311G+ (d, p) was used to simulate the molecular dynamics of the repeating component (cellobiose) of the cellulose paper. Theoretical spectra were consistent with experiment, which had absorption peaks at 0.18, 0.82, 1.47, and 1.53 THz in the same frequency range. At the same time, the paper samples after various aging intervals had different refractive indexes, and least squares fitting revealed a linear relationship between the degree of polymerization and the refractive index of the paper. Hence, this paper demonstrates that THz-TDS could be used to analyze the aging condition of transformer insulation paper and provides the theoretical and experimental basis for detection.

scholarly journals Determination of the region of the limiting states occurrence in RVS-20000 with the subsidence of the external bottom contour

2018 ◽  
Vol 239 ◽  
pp. 06002
Author(s):  
P.V. Chepur ◽  
A.A. Tarasenko ◽  
A.A. Gruchenkova
Keyword(s):  
Technical Condition ◽  
Element Analysis ◽  
Metal Structures ◽  
Software Complex ◽  
Managerial Decisions ◽  
The Finite Element Analysis ◽  
Steel Tank ◽  
Intrinsic Stiffness ◽  
Bottom Contour

The problem of the limiting states occurrence in the structures of a vertical steel tank is investigated in this work. To study the SSS of the metal structures of the object, the authors created a numerical model of the RVS-20000 tank in the ANSYS software complex. The model considers the maximum number of elements with their geometry and connections affecting the tank SSS under non-axisymmetric loading, including beyond the elasticity of steel. Dependences between the parameters of intrinsic stiffness of the VST are obtained. The results of the finite element analysis made it possible to develop a technique for assessing the technical condition of the structure with the development of irregular subsidence of the external bottom contour. The proposed technique can be used by both operating and design organizations in making managerial decisions regarding the repair of RVS-20000 subjected to the base subsidence.

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