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Reference: ISH2015_106

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Computational Dielectric Stress Analysis for OLTCs throughout the Product Lifecycle



On-load tap-changers (OLTCs) are devices that permit the change of the turn ratios of transformers without interrupting the load current. They are indispensable for the regulation of electric power and voltage in today's energy networks. A decisive aspect for the selection and design of OLTCs is their insulation co-ordination. Nowadays detailed 3D numerical modelling can strongly support the evaluation and improvement of the insulation co-ordination. The numerical modelling consists of two components: First, an electric field calculation, which can be done using standard commercial software packages. Secondly, an assessment method, that allows for the interpretation of the calculated field distribution, enabling the possibility to decide if a certain field distribution is critical or not or if one distribution is more critical than another. This assessment method usually incorporates company internal knowledge and experience. In this article we are going to give an overview of how detailed finite element simulations in combination with the streamer criterion are applied as a tool for insulation co-ordination in OLTC design and the insulation co-ordination with respect to its environment in the transformer. We will present different examples representing different stages of the product lifecycle of an OLTC. Particularly, we will show examples representing the stage of basic understanding, the early design phase, the product development stage, and finally the asset management stage. We will also explain the different goals of computationally based stress analysis during these stages, e.g. a shorter development time or the creation of general insight, as well as its different roles, i.e. if decision-making relies on a combination of computer simulation and physical tests or exclusively on computer simulation.

File Size: 806,9 KB

Year: 2015

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