| 1. |
- Magnusson, Jesper, 1984-, et al.
(författare)
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Design Aspects of a Medium Voltage Hybrid DC Breaker
- 2014
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Ingår i: 5th IEEE/PES Innovative Smart Grid Technologies Europe (ISGT EUROPE) 2014.
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Konferensbidrag (refereegranskat)abstract
- With increased demands on energy efficiency and stability, the use of direct current (DC) will have a natural place in the future smart grid. Today DC is mostly used in high voltage, high power transmission over large distances and in low voltage systems where the demands on reliability are high, e.g. data centres. New applications as wind farm collection grids and a desire to replace over-head lines with cables opens possibilities for DC distribution grids in medium voltage.The use of DC grids will require the development of DC breakers to handle fault in the grid. This paper presents the design aspects of a hybrid DC breaker for a medium voltage application. Since the hybrid topology consists of a mechanical switch as well as semiconductor components and metal oxide varistors, the design must handle trade-offs in performance and cost both for each part and also between the different components.
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| 2. |
- Magnusson, Jesper, 1984-, et al.
(författare)
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Optimal design of a medium voltage hybrid fault current limiter
- 2014
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Ingår i: 2014 IEEE International Energy Conference, ENERGYCON. - : IEEE Computer Society. - 9781479924493 ; , s. 431-438
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Konferensbidrag (refereegranskat)abstract
- The connection of distributed generation increases the short circuit power which in turn might exceed the ratings of the installed circuit breakers. A solution is to limit the available short circuit power by increasing the grid impedance, but since there is a constant strive for lower losses and higher power transfer capabilities, this is not desired. The application of a fault current limiter (FCL) that can limit the current before the first peak enables a power system with high short circuit power and low short circuit current. This can increase the stability of the grid and reduce the requirements of other equipment. This work presents a simulation model to be used as an aid in the design of a hybrid FCL for a 12 kV AC system. The proposed model combines a transient analysis circuit model with an optimization module to obtain multiple sets of possible design parameters. The design is not straight forward since there is a trade-off between several of the design parameters.
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| 3. |
- Tavakoli, Hanif, et al.
(författare)
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Localization of mechanical deformations in transformer windings using time-domain representation of response functions
- 2014
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Ingår i: European transactions on electrical power. - : Hindawi Limited. - 1430-144X .- 1546-3109. ; 24:1, s. 16-29
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Tidskriftsartikel (refereegranskat)abstract
- Time domain reflectometry (TDR) has been used for localization of discontinuities in transmission lines in diverse applications. In this paper, its potential as an alternative to frequency response analysis for the detection and localization of mechanical changes (damages) in transformer windings is investigated. This is done by computer simulations of a lumped-element circuit model of a disc winding which has been verified with measurements on an experimental coil. We also suggest that the idea of TDR can be used to visualize the results of frequency response measurements in time domain, where they are easier to interpret. When applying TDR to transformer windings instead of transmission lines, two main new problems have to be addressed, namely (i) the basic inhomogeneity of most winding designs, and (ii) the strong effect of dispersion (distortion of signals as they travel along the winding). We argue that TDR is still useful under these circumstances if it is applied as a differential method and in the right frequency window, i.e. using signals of suitable shapes. Under these conditions, it allows the detection and, to some extent, localization of certain mechanical changes in a transformer winding.
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