05 Fakultät Informatik, Elektrotechnik und Informationstechnik

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/6

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Publication Type: search.filters.UBSTyp.ZeitschriftenartikelStart date: 2019End date: 2019Subject: search.filters.subject.621.3Institute: search.filters.UBSInstitut.Fakultätsübergreifend / Sonstige Einrichtung

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    Quantitative analysis of the sensitivity of UHF sensor positions on a 420 kV power transformer based on electromagnetic simulation
    (2019) Beura, Chandra Prakash; Beltle, Michael; Tenbohlen, Stefan; Siegel, Martin
    With an increasing interest in ultra-high frequency (UHF) partial discharge (PD) measurements for the continuous monitoring of power transformers, it is necessary to know where to place the UHF sensors on the tank wall. Placing a sensor in an area with many obstructions may lead to a decrease in sensitivity to the UHF signals. In this contribution, a previously validated simulation model of a three-phase 300 MVA, 420 kV power transformer is used to perform a sensitivity analysis to determine the most sensitive sensor positions on the tank wall when PD activity occurs inside the windings. A matrix of UHF sensors located on the transformer tank is used to perform the sensitivity analysis. Some of the windings are designed as layer windings, thus preventing the UHF signals from traveling through them and creating a realistic situation with very indirect propagation from source to sensor. Based on these findings, sensor configurations optimized for UHF signal sensitivity, which is also required for PD source localization, are recommended for localization purposes. Additionally, the propagation and attenuation of the UHF signals inside the windings and the tank are discussed in both oil and air.
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    ItemOpen Access
    Measuring test bench with adjustable thermal connection of cells to their neighbors and a new model approach for parallel-connected cells
    (2019) Fill, Alexander; Mader, Tobias; Schmidt, Tobias; Llorente, Raphael; Birke, Kai Peter
    This article presents a test bench with variable temperature control of the individual cells connected in parallel. This allows to reconstruct arising temperature gradients in a battery module and to investigate their effects on the current distribution. The influence of additional contact resistances induced by the test bench is determined and minimized. The contact resistances are reduced from 𝑅Tab+=81.18 μΩ to 𝑅Tab+=55.15 μΩ at the positive respectively from 𝑅Tab-=35.59 μΩ to 𝑅Tab-=28.2 μΩ at the negative tab by mechanical and chemical treating. An increase of the contact resistance at the positive tab is prevented by air seal of the contact. The resistance of the load cable must not be arbitrarily small, as the cable is used as a shunt for current measurement. In order to investigate their impacts, measurements with two parallel-connected cells and different load cables with a resistance of 𝑅Cab+=0.3 mΩ, 𝑅Cab+=1.6 mΩ and 𝑅Cab+=4.35 mΩ are conducted. A shift to lower current differences with decreasing cable resistance but qualitatively the same dynamic of the current distribution is found. An extended dual polarization model is introduced, considering the current distribution within the cells as well as the additional resistances induced by the test bench. The model shows a high correspondence to measurements with two parallel-connected cells, with a Root Mean Square Deviation (RMSD) of 𝜉RMSD=0.083 A.