Abstract:With the increasing age of the primary equipment of the electrical grids there exists also an increasing need to know its internal condition. For this purpose, off-and online diagnostic methods and systems for power transformers have been developed in recent years. Online monitoring is used continuously during operation and offers possibilities to record the relevant stresses which can affect the lifetime. The evaluation of these data offers the possibility of detecting oncoming faults early. In comparison to this, offline methods require disconnecting the transformer from the electrical grid and are used during planned inspections or when the transformer is already failure suspicious. This contribution presents the status and current trends of different diagnostic techniques of power transformers. It provides significant tutorial elements, backed up by case studies, results and some analysis. The broadness and improvements of the presented diagnostic techniques show that the power transformer is not anymore a black box that does not allow a view into its internal condition. Reliable and accurate condition assessment is possible leading to more efficient maintenance strategies.

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There has been an ongoing conversation about the role and relationship of theory and practice in the HCI community. This paper explores this relationship privileging a practice perspective through a tentative model, which describes a "bubble-up" of ideas from practice to inform research and theory development, and an accompanying "trickle-down" of theory into practice. Interviews were conducted with interaction designers, which included a description of their use of design methods in practice, and their knowledge and use of two common design methods-affinity diagramming and the concept of affordance. Based on these interviews, potential relationships between theory and practice are explored through this model. Disseminating agents already common in HCI practice are addressed as possible mechanisms for the research community to understand practice more completely. Opportunities for future research, based on the use of the tentative model in a generative way, are considered.

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student goes on a journey; stranger rides into the classroom: narratives and the instructor in the design studio abstract Enthusiasm is growing in non-traditional environments for teaching design by adapting knowledge and approaches from studio pedagogy, described as a 'signature pedagogy' by Lee S. Shulman in 2005. Meanwhile, those in fields where some variation of studio pedagogy have been used for decades are engaged in addressing some of its experienced shortcomings. Within this landscape of change, the authors have been engaged in study of their own studio-based courses, (interior design, instructional design, and interaction/experience design), reflecting on how this form of pedagogy is contributing to students' development as designers. In this study we consider the role of the instructor in the studio using a lens informed by narrative aesthetics and transformative education. The narrative that an instructor encourages students to experience with regard to themselves, to the instructor, or to both, has a profound impact in the studio environment. This article will explore that impact within the

The continuous, non-intermitted service of electrical grids relies on the reliability of their assets, e.g., power transformers. Local insulation defects can result in serve failures such as breakdowns with severe subsequent costs. The prevention of such events is crucial. Hence, partial discharge (PD) activity at power transformers is evaluated directly in the factory before shipment. Additionally, PD activity can be monitored during service using the ultra-high frequency (UHF) method. In this contribution, a calibration procedure is proposed for the UHF method. The calibration process is required to ensure both, reproducibility and comparability of UHF measurements: Only a calibrated UHF measurement procedure can be introduced supplementary to IEC 60270 in acceptance tests of power transformers. The proposed calibration method considers two factors: The influence of the UHF-antenna's sensitivity and the PD recorder characteristics including accessories such as cable damping, pre-amplifier, etc. The former is addressed by a characterization of UHF sensors using the standard antenna factor (AF) in a gigahertz transverse electromagnetic (GTEM) cell. The PD recorder's influence is corrected by using a defined, invariable test signal as reference for all recording devices. A practical evaluation of the proposed calibration procedure is performed in a laboratory setup using different UHF recording devices and UHF sensors using artificial PD signals and real voltage-driven PD sources.

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