scholarly journals THE DEGREE OF POLYMERIZATION OF POWER TRANSFORMERS’ PAPER INSULATION

2019 ◽  
Vol 20 (9-10) ◽  
pp. 34-38 ◽  
Author(s):  
V. K. Kozlov ◽  
A. Kh. Sabitov
Keyword(s):  
Aging Time ◽  
Thermal Aging ◽  
Manufacturing Process ◽  
Degree Of Polymerization ◽  
Power Transformers ◽  
Aging Rate ◽  
Slowing Down ◽  
Starting Time ◽  
Exponential Decrease ◽  
Paper Insulation

The paper presents the results of research and analysis of literature data on the paper insulation's thermal aging. An exponential decrease in the degree of polymerization of paper insulation from the aging time is established, at the starting time of transformers’ operation the aging rate of paper insulation is maximal and after that its slowing down. It was found out that the degree of polymerization at the starting time of the transformer's operation can be in the range of 900 units, this is due to its drying during the manufacturing process.

scholarly journals Analysis of Operating Modes of Oil-Immersed Power Transformers with a Voltage of 10 (6) / 0.4 kV

2021 ◽  
Vol 24 (4) ◽  
pp. 80-91
Author(s):  
A.E. Fokeev ◽  
I.N. Tumakov
Keyword(s):  
Ambient Temperature ◽  
Thermal Aging ◽  
Power Transformer ◽  
Spectral Composition ◽  
Operating Conditions ◽  
Power Transformers ◽  
Load Factor ◽  
Calculation Algorithm ◽  
Load Current ◽  
Aging Rate

The rate of thermal aging of the power transformers windings insulation depends on the effects of the electric field, mechanical stresses, temperature and processes that cause changes in these factors. A calculation algorithm is considered that allows determining the temperature of the most heated point of the windings of an oil power transformer at known values of the load current and ambient temperature. Calculation of the most heated winding point temperature and the rate of thermal aging of insulation for an oil power transformer at different ambient temperatures during the year, different values and different spectral composition of the electric load current showed that in some cases it is possible to violate the permissible operating conditions of power transformers. According to the calculation results, the dependences of the thermal aging rate of insulation on the ambient temperature are constructed, with different load parameters and different load coefficients of power transformers. For the considered modes, in the warm season, the value of the thermal aging rate of insulation significantly exceeds the nominal value. Based on mathematical models of oil power transformers with natural and forced oil circulation, expressions are obtained for determining the coefficient of reduction of the oil power transformers permissible load when the ambient temperature exceeds the normal value of 20 °C. On the basis of these expressions, for practical use, the dependences of the coefficient of reduction of the permissible load on the ambient temperature are constructed. The influence of ambient temperature must be taken into account when choosing the power of oil power transformers, for which it is assumed to operate in full redundancy mode or high load factor values (³ 0.8) in normal mode. To ensure the normative service life of the insulation of the windings, it is necessary to determine the design power of oil power transformers using the coefficient of reduction of the permissible load under the influence of higher harmonics of the current and the coefficient of reduction of the permissible load under the influence of ambient temperature.

scholarly journals Comparative Study on the Thermal-Aging Characteristics of Cellulose Insulation Polymer Immersed in New Three-Element Mixed Oil and Mineral Oil

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1292 ◽  
Author(s):  
Dawei Feng ◽  
Jian Hao ◽  
Ruijin Liao ◽  
Xin Chen ◽  
Lin Cheng ◽  
...  
Keyword(s):  
Comparative Study ◽  
Breakdown Voltage ◽  
Thermal Aging ◽  
Cellulose Degradation ◽  
Mineral Oil ◽  
Aging Rate ◽  
Cellulose Paper ◽  
Paper Insulation ◽  
Cellulose Insulation ◽  
Insulation Oil

Cellulose paper, whose main component is cellulose polymer, has been widely used in oil-immersed power transformer that gradually deteriorates during transformer operation. Thermal aging is the main degradation form for cellulose paper immersed in insulation oil (oil–paper insulation) in a transformer. One of the most challenging issues in oil–paper insulation is inhibiting the aging of cellulose paper and extending its life. In this work, a comparative study was conducted on the thermal-aging characteristics of cellulose paper immersed in a novel three-element mixed insulation oil and mineral oil at 130 °C for 150 days. The key parameters of cellulose paper were analysed, including the degree of polymerization (DP), thermal-aging rate, surface colour, and AC breakdown voltage. The furfural content and acidity of the oil, as well as the AC breakdown voltage of the insulation oil were also analysed. The results show that the cellulose paper immersed in novel three-element mixed insulation oil had much higher DP values than that immersed in mineral oil after the same thermal-aging time. The mixed insulation oil could significantly inhibit the thermal aging of cellulose paper and prolong its life. The thermal-aging rate of the cellulose insulation polymer immersed in mixed insulation oil is significantly lower than that immersed in mineral oil, whether in the process of oil–paper insulation continuous aging or in the process of aging after oil replacement with unused insulation oil. The furfural generated by cellulose degradation in the novel three-element mixed insulation oil was also less than that in the mineral oil. The mixed insulation oil had a higher acidity value during the thermal-aging process, which was mainly due to the natural esters in the components of the mixed insulation oil. However, the AC breakdown voltage of the mixed insulation oil was always higher than that of the mineral oil. This study offers a new perspective in inhibiting the thermal aging of cellulose polymer in insulation oil.

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 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.

scholarly journals Effect of Thermal Aging on the Mechanical Properties of High Tenacity Polyester Yarn

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1666
Author(s):  
Tsegaye Sh. Lemmi ◽  
Marcin Barburski ◽  
Adam Kabziński ◽  
Krzysztof Frukacz
Keyword(s):  
Mechanical Properties ◽  
Structural Change ◽  
Aging Time ◽  
Thermal Aging ◽  
Temperature Influence ◽  
Polyester Yarn ◽  
Textile Materials ◽  
Conveyor Belts ◽  
Effects Of Aging ◽  
Vulcanization Process

Textile materials produced from a high tenacity industrial polyester fiber are most widely used in the mechanical rubber goods industry to reinforce conveyor belts, tire cords, and hoses. Reinforcement of textile rubber undergoes a vulcanization process to adhere the textile materials with the rubber and to enhance the physio-mechanical properties of the product. The vulcanization process has an influence on the textile material being used as a reinforcement. In this work, the effects of aging temperature and time on the high tenacity polyester yarn’s mechanical and surface structural properties were investigated. An experiment was carried out on a pre-activated high tenacity polyester yarn of different linear densities, by aging the yarn specimens under various aging temperatures of 140, 160, 200, and 220 °C for six, twelve, and thirty-five minutes of aging time. The tensile properties and surface structural change in the yarns pre- and post-aging were studied. The investigation illustrates that aging time and temperature influence the surface structure of the fiber, tenacity, and elongation properties of the yarn. Compared to unaged yarn, an almost five times higher percentage of elongation was obtained for the samples aged at 220 °C for 6 min, while the lowest tenacity was obtained for the sample subjected to aging under 220 °C for 35 min.

Effects of thermal aging on moisture equilibrium in oil-paper insulation

2018 ◽  
Vol 25 (6) ◽  
pp. 2340-2348 ◽  
Author(s):  
Dongyang Wang ◽  
Lijun Zhou ◽  
Xianlang Li ◽  
Yi Cui ◽  
Huize Li ◽  
...  
Keyword(s):  
Thermal Aging ◽  
Paper Insulation

Microstructural Evaluation of Isothermally Aged 12Cr Steel by Magnetic Property Measurement

2006 ◽  
Vol 324-325 ◽  
pp. 1253-1256
Author(s):  
C.S. Kim ◽  
J.H. Kang ◽  
Jai Won Byeon ◽  
S.I. Kwun
Keyword(s):  
Mechanical Properties ◽  
Magnetic Property ◽  
Aging Time ◽  
Thermal Aging ◽  
Isothermal Aging ◽  
Martensite Lath ◽  
M23c6 Carbide ◽  
Linear Relations ◽  
Microstructural Evaluation ◽  
Property Measurement

The magnetic coercivity of ferritic 12Cr steel was experimentally studied in order to characterize its microstructures and mechanical properties during isothermal aging. As the aging time increased, the M23C6 carbide coarsened and additional precipitation of Fe2W phase was induced. The width of martensite lath increased to about 0.4μm after 4000 hrs of aging. The coercivity decreased as the number of precipitate decreased and the width of martensite lath increased. The hardness was proportional to the magnetic coercivity. These empirical linear relations suggested that the change in the microstructures and strength of ferritic 12Cr steel during thermal aging could be evaluated by monitoring the magnetic coercivity.

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