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- Elg, Alf Peter, et al.
(författare)
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Research project EMPIR 19ENG02 future energy
- 2020
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Ingår i: VDE High Voltage Technology 2020. - : VDE Verlag GmbH. - 9783800753550 ; , s. 252-257
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Konferensbidrag (refereegranskat)abstract
- Society's increasing demand for electrical energy, along with the increased integration of remote renewable generation has driven transmission levels to ever higher voltages in order to maintain (or improve) grid efficiency. Consequently, high voltage testing and monitoring beyond voltage levels covered by presently available metrology infrastructures are needed to secure availability and quality of supply. Calibration services for Ultra-High Voltage Direct Current (UHVDC) presently are only available up to 1000 kV. There is a need to extend the DC calibration capabilities for voltage instrument transformers up to 1200 kV and for factory component testing capabilities up to 2000 kV. Also, methods for linear extension of lightning impulse calibration, for dielectric testing of UHV grid equipment, urgently need revision. Recent research has raised questions regarding the validity of the current linearity extension methods for voltages beyond 2500 kV. Furthermore, new methods for calibration are needed for the 0.2 class HVAC voltage instrument transformers for system voltages up to 1200 kV. The current methods used for determination of the voltage dependence are very time consuming, raising the need for methods allowing faster assessment. Finally, with new HVDC transmission grids and associated components, novel methods are needed for detection, classification and localisation of partial discharge (PD) under DC stress. The industry needs methods for reliable monitoring of critical components such as cables, for both HVAC and HVDC, and gas insulated substations (GIS), and techniques for addressing new challenges introduced by HVDC technologies, such as the ability to distinguish PD signals from switching transients in converters and other sources of noise.
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- Meisner, J., et al.
(författare)
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Support for standardisation of high voltage testing with composite and combined wave shapes
- 2021
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Ingår i: VDE High Voltage Technology. - : VDE Verlag GmbH. - 9783800753550 ; , s. 354-358
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Konferensbidrag (refereegranskat)abstract
- As part of the production of equipment for high voltage electricity grids, high voltage tests are performed to verify that the equipment can withstand the operational voltage stresses. Such 'withstand tests' are performed using combined and composite waves, where lightning impulse (LI) or switching impulse (SI) waves are superimposed on AC or DC. Both the technical understanding of the generation and measurement of such high voltage wave forms and the regulations in international standards are not sufficient for the current requirements. Therefore, a European metrology project with industrial partners, universities and seven European metrology institutes (NMI) is started in 2020. In three technical work packages the metrological and standardisation need will be issued. First, the relationship between impulse voltages with AC or DC measurement, and related detrimental effects due to combining wave shape tests will be reliably determined. New measurement instruments, low voltage generators and measurement evaluation software will be created. Traceable high voltage measurement systems and calibration services for composite and combined wave shapes, with a target amplitude uncertainty of less than 2 % will be developed at the NMIs. The capabilities of these NMIs will be confirmed with aid of a high voltage comparison campaign at PTB. The uncertainty of existing voltage dividers and measuring systems used in tests with composite and combined wave shapes will be accurately determined. Finally, the research results will be forwarded to the ongoing revision of the IEC 60060 series.
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- Lahti, K., et al.
(författare)
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Productivity Aspects in Submerged Arc Welding of Thick High-Strength Steels
- 2015
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Ingår i: Proceedings of IIW International Conference, High-Strength Materials. - Helsingfors. ; , s. 1-6-
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Konferensbidrag (refereegranskat)abstract
- A series of welding tests were made on 35 mm thick F500W high strength steel. This specific steel grade is developed for use in arctic conditions, especially in shipbuilding, and it has excellent impact toughness at temperatures down to -60°C. Submerged arc welding tests were performed using solid and flux-cored welding wire keeping the heat-input at levels typically recommended for thermo mechanically processed highstrengthsteels. Process improvement trials were even made using electrode extension (EE) allowing for higher melt-on rates without any increase in the heat input.However, as the chemical composition of F500W allows for higher heat input without risk for excessive grain growth, tests at higher heat inputs were also made as reference for additional ways to increase productivity. Three fundamental means for improving productivity were analyzed in this study: 1) use of solid or flux-cored wire, 2) effect of groove preparation, and 3) use ofelectrode extension. These all can be introduced without changes in heat input, and hence implementation to existing production systems is easy, economical and quick. Highest increase in productivity is gained by using electrode extension with optimized groove geometry. In the studied thickness of 35 mm, the number of runs was decrease by 60 % from 22 to 9 without increase in the heat input and with approved mechanical properties for this specific steel. Based on the outcome of this study, submerged arc welding can successfully be used for joining of this high strength steel with approved mechanical properties and high productivity.
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