| 1. |
- Garnacho, F., et al.
(författare)
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Metrological Qualification of PD Analysers for Insulation Diagnosis of HVDC and HVAC Grids
- 2023
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Ingår i: Sensors. - : Multidisciplinary Digital Publishing Institute (MDPI). - 1424-8220. ; 23:14
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Tidskriftsartikel (refereegranskat)abstract
- On-site partial discharge (PD) measurements have turned out to be a very efficient technique for determining the insulation condition in high-voltage electrical grids (AIS, cable systems, GIS, HVDC converters, etc.); however, there is not any standardised procedure for determining the performances of PD measuring systems. In on-line and on-site PD measurements, high-frequency current transformers (HFCTs) are commonly used as sensors as they allow for monitoring over long distances in high-voltage installations. To ensure the required performances, a metrological qualification of the PD analysers by applying an evaluation procedure is necessary. A novel evaluation procedure was established to specify the quantities to be measured (electrical charge and PD repetition rate) and to describe the evaluation tests considering the measured influence parameters: noise, charge amplitude, pulse width and time interval between consecutive pulses. This procedure was applied to different types of PD analysers used for off-line measurements, sporadic on-line measurements and continuous PD monitoring. The procedure was validated in a round-robin test involving two metrological institutes (RISE from Sweden and FFII from Spain) and three universities (TUDelft from the Netherlands, TAU from Finland and UPM from Spain). With this round-robin test, the effectiveness of the proposed qualification procedure for discriminating between efficient and inappropriate PD analysers was demonstrated. Furthermore, it was shown that the PD charge quantity can be properly determined for on-line measurements and continuous monitoring by integrating the pulse signals acquired with HFCT sensors. In this case, these sensors must have a flat frequency spectrum in the range between several tens of kHz and at least two tens of MHz, where the frequency pulse content is more significant. The proposed qualification procedure can be useful for improving the future versions of the technical specification TS IEC 62478 and the standard IEC 60270. © 2023 by the authors.
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| 4. |
- Draxler, K., et al.
(författare)
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International comparison of current transformer calibration systems up to 10 kA at 50 Hz frequency
- 2016
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Ingår i: 2016 Conference on Precision Electromagnetic Measurements (CPEM 2016). - 9781467391344
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Konferensbidrag (refereegranskat)abstract
- Current transformers (CTs) are precision devices that scale high currents down to values that can be easily handled by measurement equipment. To support CT applications in revenue metering, a comparison on AC current transformer calibration systems was performed among 15 European national metrology institutes using a precision CT as the travelling device. The first comparison results for the transformation ratios (4, 5, 6, 8, 10) kA/5 A of the travelling CT at nominal burden of 5 VA and 15 VA indicate good agreement between the participating laboratories. The main differences are found for phase displacement, at least partly caused by the instability of the traveling standard.
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| 5. |
- Draxler, K., et al.
(författare)
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Results of an International Comparison of Instrument Current Transformers up to 10 kA at 50 Hz Frequency
- 2018
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Ingår i: CPEM 2018 - Conference on Precision Electromagnetic Measurements. - 9781538609736
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Konferensbidrag (refereegranskat)abstract
- Traceability of the current ratio is crucial for the measurement of electrical energy in revenue metering. A comparison of the AC current ratio was therefore performed within EURAMET in the time period 2012-2016, using a precision CT as the traveling device. The Czech Metrology Institute (CMI) as coordinator processed the measurement results of the 15 European participating laboratories. The comparison of the results for transformer ratios of (4, 5, 6, 8, 10) kA 5 A at 15 VA burden and (4 and 10) kA 5 A ratios at 5 VA burden indicates good agreement between the participating laboratories. The main differences are found for phase displacement, at least in part due to instability of the traveling standard. .
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| 6. |
- 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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| 7. |
- Hallström, J., et al.
(författare)
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Worldwide comparison of lightning impulse voltage measuring systems at the 400-kV level
- 2007
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Ingår i: IEEE Transactions on Instrumentation and Measurement. - 0018-9456 .- 1557-9662. ; 56:2, s. 388-391
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Tidskriftsartikel (refereegranskat)abstract
- An international comparison of lightning and switching impulse voltage measuring systems was arranged and coordinated by the Helsinki University of Technology (MIKES-TKK), Espoo, Finland, between 1999 and 2002. The number of participants was 26, including the coordinator. This paper summarizes the results obtained by those eight National Metrology Institutes that participated in the comparison. A 400-kV transfer reference measuring system for measuring lightning impulse voltages was prepared by the coordinator. In addition, a 1-kV impulse voltage calibrator system, including calibrators for both standard lightning and switching impulses, was circulated. © 2007 IEEE.
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| 8. |
- Hällström, J, et al.
(författare)
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International comparison of software for calculation of lightning impulse parameters based on a new processing algorithm
- 2007
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Konferensbidrag (refereegranskat)abstract
- A new algorithm has been proposed to calculate the parameters of full lightning voltage impulses. The new algorithm enables the application of the test voltage factor (also referred to as k-factor in some literatures) for calculation of the equivalent test voltage of impulses with superimposed oscillations/overshoots. The new algorithm at the same time provides a robust procedure for obtaining time parameters of the impulses from not only smooth waveforms but also waveforms with varying degrees of distortions in the front part of the impulses. These distortions include oscillations on the impulse front and overshoots in the peak region. A critical part of the new algorithm is a 4-parameter fitting procedure to obtain the base curve, which is used for calculation of the test voltage curve. Another important part of the algorithm is applying a filtering procedure in the calculation of the test voltage curve. The new algorithm was tested in different laboratories using different programming languages and different techniques for realising the fitting and filtering routines. The paper reports the results obtained from the participating laboratories using the proposed algorithm. The results obtained by the participating laboratories using existing software based on the requirement of IEC 60060-1: 1989 were also compared. It is anticipated that the results can serve as a part of the basis for a new procedure for determination of lightning impulse parameters in the revised IEC 60060-1.
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| 10. |
- 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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