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The synthetic aperture radar (SAR) imaging method has been recently proposed for online radial deformation detection of high voltage transformer windings. In this method, electromagnetic waves should be transmitted toward the transformer windings through an antenna. The antenna should be moved along the height of the transformer. Since electromagnetic waves cannot penetrate the metal tank, a window is required on the body of the transformer tank to transmit waves toward the winding. The proper design of such a window and investigation of SAR imaging methods with the existence of it, is necessary to make the previous SAR imaging studies applicable to the transformer winding. Therefore, in order to study the design and implementation of a dielectric window, a prototype of a tank with a dielectric window is built considering electrical and mechanical constraints. The experimental results show the feasibility of applying the SAR imaging for localisation of radial deformation with the existence of a dielectric window in real transformers. [ABSTRACT FROM AUTHOR]

Optimal placement and sizing of distributed energy resources (DERs) can be performed from various points of view. In this paper, a multiobjective function is employed to determine optimal place and size of DERs including combination of photovoltaic resources and a small-scale synchronous generator (SSSG) with an internal combustion engine as its prime mover. As the objective function, not only minimization of investment costs, operation costs, and system losses are used, but also the voltage of microgrid (μG) busses and current of lines are considered as constraints. In addition, this paper shows mechanical stresses can be imposed on the SSSG caused by generator swings after short circuit fault clearing. Furthermore, it may lead to mechanical fatigue in its associated shaft and prime mover. Meanwhile, it is revealed that the mechanical stresses depend on the DERs placement and size. Thus, a novel index representing the stresses on the SSSG shaft is applied in the multiobjective goal function. This decreases SSSG loss of life in a μG with overhead lines which has high rate of short circuit faults. Optimization studies are performed in a six-bus and four-DER μG using time-based simulations. [ABSTRACT FROM AUTHOR]