Abstract:The joint is the weakest link in three-core medium-voltage power cable systems and the temperature is an essential indicator to its insulation condition. Therefore, a model to estimate the temperature inside the three-core cable joint was built based on support vector regression (SVR) with two fixed cable surface temperatures as inputs. The samples for model training were obtained from 3-D transient thermal analyses through finite element method (FEM) under different single-step currents. A temperature-rise test of 15 kV three-core cable joint was carried out and the estimated temperature based on SVR agrees well with the measured result with a maximum error of about 4 • C. Besides, the proposed model could accurately estimate the joint temperature even though the thermal conductivity of armor wrap used in thermal analysis for model training differs from its real value. The accuracies and calculation speed of the proposed model were compared with those of FEM, showing a better generality of our model. A temperature-rise test under unbalanced three-phase currents was performed and the temperature estimation errors are within 6 • C, indicating the applicability of the method. The effect of contact resistance was briefly discussed in the end. This approach helps improve cable operation and maintenance.
The transformer bushing hot spot temperature (HST) seriously affects its performance and design. In this paper, a novel method for calculating the hot spot temperature of bushing is proposed, in which the principle of constant joule heat is adopted to transform the fluctuating current into the steady-state current. Firstly, the fluctuating current based on time is segmented. Then, the fluctuating current in each period of time is transformed into steady-state current which is used as heat source. Next, the Finite Element Method (FEM) is used to determine a typical bushing's temperature distribution and specify its hot spot. According to the calculation results of hot spot temperature rise, the time interval is adjusted. Finally, the optimal time interval and the steady-state equivalent current are obtained by solving the hot spot temperature of the transformer bushing iteratively. In addition, the method is used to calculate the hot spot temperature of a 220kV Oil Impregnated Paper (OIP) bushing. Compared with the results of traditional transient calculation method, the validity of the proposed method is verified, and the computing time is greatly reduced.
The arflhor has granted a nonexclusive licence allowing the National Library of Canada to reproduce, loan, distribute or sell copies of this thesis in microform, paper or electronic formats. The ar¡thor retains ownership of the copyright in this thesis. Neither the thesis nor substantial extacts from it may be printed or otherwise reproduced without the author's permission. You ñl€ Voua úlêrênca Out ñl€ Nols îélércflco L'auter¡r a accordé une licence non exclusive permettant à la Bibliothèque nationale du Canada de reproduire, prêter, distribuer ou vendre des copies de cette thèse sous la forme de microfiche/fiI¡o" de reproduction sur papier ou sur format électronique. L'auteur conserve la propriété du droit d'auteur qui protège cette thèse. Ni la thèse ni des extraits substantiels de celle-ci ne doivent ête imprimés ou autrement reproduits sâns son autorisation. Canadä 0-612-79901-8 TET', TINTYERSITY OF' MANITOBA FACULTY OF GRADUATE STI]DIES ***** COPYRIGHT PERMISSION PAGE MODELLING OF HVDC WALL BUSHING FLASHO\{ER DIIE TO UNEVEN WETTING A ThesislPracticum submitted to the Faculty of Graduate Studies of The University of Manitoba in partial fulfillment of the requirements of the degree of Doctor of Philosophy LIANG TANG @ 2OO2 BY LIANG TANG Permission has been granted to the Library of The University of Manitoba to lend or sell copies of this thesis/practicum, to the National Library of Canada to microfihn this thesis and to lend or sell copies of the film, and to University Microfilm Inc. to publish an abstract of this thesis/practicum. The author reserves other publication rights, and neither this thesis/practicum nor extensive extracts from it may be printed or otherwise reproduced without the author's written permission. One of the serjous problems in H\aDC transmission is that of rvall bushing flashover initiated by rain, fog or wet snov. Äll utilities engaged in dc transmission experìence such problems and have adopted counteffneasures with varying degtees of success. The consensus of opinion is that there is a need to better understand the phenomena and devise effective remedial measu.res or an improved desþ. The problem of H\IDC rvall bushing flashor.er due ro uneven rvetting is introduced and tevierved, with emphasis ori recent progress in understanding the phenomena. The physics of discharges, particularly for flashover of an unevenly rvetted H\IDC rvall bushing, is discussed and various processes and mechanisms tesponsible for discharge initiation and propagation are clarified and discussed in detail. ,4. numerical model is developed in order to predict flashover voltages for a wall bushing based on the results of accurate electrjc field computadon carlj.ed out on a bushing, prior to initiating flashover. This analysis is done under a variety of practical conditions. The simuladon results are in agreement with experimental data and, in general, explain rvell certain aspects of uneven rvetting flashover. The results of this research, particularþ the proposed models are important supplements to large-sca...
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