Andritz (Austria)

Abstract Systematic measuring of hydraulic machine's performance data at hydraulic model test rigs involves comprehensive expert knowledge of the test rig engineer and is time-consuming, as the multidimensional operation space must be explored manually. Expertise is needed to account for specific performance limits of test-rig equipment, model turbines, storage pumps, or pump turbines as well as some hysteresis of the setup due to flow separation and dealing with operation point-dependent gains between controlled parameters and measured quantities. To free valuable manpower from the burden of shift work, the measurement procedure is subject to automation. However, testing new automation concepts involves safety-critical or expensive tests and consumes valuable time at tests too. To develop and validate new automation concepts offline, we present a hybrid data-driven modeling approach to create a digital twin of the combined setup of a hydraulic turbine on a hydraulic test rig. Special attention paid to the modeling approach is consistent with existing mathematical relations governed by either physical models or norms. The presented approach allows the separation of test rig and hydraulic model machine under test and this enables offline validation of automation concepts on different combinations of test rigs and hydraulic model machines. The modeling approach is demonstrated by performing cross-validation using recorded measurement data.

The energy transition, i.e. the strategic change from fossil fuels to renewable energy sources, entails a fundamental transformation of the transmission and distribution grids. The electric power system is in transition which shifts from a rotating mass-dominated system to a power converter-dominated system. Without the appropriate measures, this will have a negative impact on power system stability. This report describes the implications of the transformation of the electric power system o n voltage stability and frequency stability, it compares Synchronous Condensers (SynCon), SVCs (static VAR compensation) and static synchronous compensators (STATCOM) with regard to the different grid needs. SynCons, which have been used for reactive power compensation since the early 20th century, and have been replaced by other technologies in the meantime, are experiencing a renaissance in transmission and distribution grids [1].

Industrial Product-Service Systems (IPSS) are increasingly dominant in several sectors. Predominant value-adding services provided for industrial assets such as production systems, electric power plants, and car fleets are remote asset maintenance, monitoring, control, and reconfiguration. IPSS designers lack methods and tools supporting them in systematically deriving technical design requirements for the underlying Cyber-Physical System (CPS) IPSS services. At the same time, the use of Digital Twins (DTs) as digital representations of CPS as-sets is becoming increasingly feasible thanks to powerful, networked information technology (IT) and operation technology (OT) infrastructures and the ubiquity of sensors and data. This paper proposes a method for guiding IPSS designers in the specification and implementation of DT instances to serve as the key enablers of IPSS services. The systematic mapping of the continuous IT design-build-deployment cycle concept to the OT domain of CPS is at the heart of the applied methodology, which is complemented by a stakeholder-driven requirements elicitation. The key contribution is a structured method for deriving technical design requirements for DT instances as IPSS. This method is validated on real-world use cases in an evaluation environment for distributed CPS IPSS.

The surface of tissue paper is relatively complex compared to other paper grades and consists of several overlapping structures like protruding fibres, crepe and fabric-based patterns at different spatial frequencies. The knowledge of tissue surface characteristics is crucial when it comes to improvement with respect to surface softness and the perceptual handfeel of tissue products. In this work we used the optical based, non-contact measurement principle of focus variation for surface characterization of dry-creped, textured and through air dried (TAD) tissue. Based on the three tissue grades, a procedure which includes the characterization of the whole tissue surface throughout different scales within one setup, was developed. Surprisingly, focus variation was rarely used in tissue-related research, as it provides robust and reliable 3D surface information which can be used for further areal surface analysis. Special attention was given to the preparation and discussion of the raw data up to the final analysis including several spatial filtering steps. Enhanced surface parameters like the developed interfacial area ratio (Sdr) and the power spectral density (PSD) were used to describe the surface adequately. The surface roughness of the three tissue grades was compared, with the textured tissue showing the highest roughness in Sdr and PSD analysis. Although both methods are based on different principles, a high correlation in terms of evaluated roughness is evident. Regular structures like crepe and patterns are obtainable as peaks at the respective frequency with a certain intensity in the PSD evaluation. Apart from topography in terms of structures and roughness, the wide field of view of the focus variation measurement also allows assessment of effects related to flocculation and sheet formation. The developed procedure could also be appropriate for other fibre based materials and/or fabrics, which are similar to tissue with respect to optical properties such as for example nonwovens.Graphic abstract

High-voltage stator windings for large salient-pole synchronous machines in hydro power applications are designed based on manufacturing, maintenance, cost and electromagnetic performance issues. This paper discusses various aspects for designing standard three-phase windings and in particular presents a novel method for minimizing the number of external connections in wave winding application. A special section is dedicated to unbalanced winding parallel circuits due to coil bypass for quick repair in the case of bar or coil failures.

Abstract Turbines or pumps in hydropower plants achieve peak efficiencies of far more than 90% depending on the specific speed and the type of machine. Based on model tests or numerical simulations, the efficiency of a prototype machine has to be guaranteed and measured with the best measurement technique available. The choice of the appropriate efficiency measurement method does not only depend on the expected measurement uncertainties and tolerances set in a contract, it is also a question of the effort required for such a measuring campaign and of technical challenges, e.g., limitations imposed by plant operating conditions as draining of the system or constant load operation. Concerning hydraulic turbomachines, modern measuring technology offers different methods for efficiency measurements at a turbine unit. Primarily through the development of real-time capable data acquisition systems, it is possible to perform high-precision measurements rather quickly, whereby minimal downtimes can be achieved. In the first part, the specific measurement methods available in different standards are presented in an overview, and then in the second part, the achieved accuracies of a very complex thermodynamic measurement are compared with a low-cost clamp-on acoustic Doppler measurement using a concrete example.

Usually it is demanded that the metric and its 1st derivatives have to match at the boundary of two adjacent regions which are solutions to Einstein’s field equation. We propose a new linking condition concerning gravitational models based on surfaces which could be embedded into a higher dimensional flat space. We probe this condition for the Schwarzschild interior and exterior solution.

The concept of fish friendliness of hydroturbines relates to the effects of a unit design and its operating conditions on the success of migratory fish survival during passage through turbine flows. Most computer-based studies of fish friendliness approximate fish trajectories with streamlines; this work introduces a particle-based method to account for collisions on two typically interrogated structures: the stator and the runner. We implemented the method in various operating points of a Kaplan turbine simulated with computational fluid dynamics. The results indicated that only a small percentile of the particle sample collides severely with the stator (<0.5%) and the runner blades (<3%). The severe collisions did not exhibit any preferential distribution in the circumferential and radial directions, except for particles to collide near the outer area of the runner (near the discharge ring). This article concentrates mainly on the advantages and limitations of the particle-based method, always assessed in view of streamline-based calculations.