| 1. |
- Jürgensen, Jan Henning, 1987-, et al.
(författare)
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Health index as condition estimator for power system equipment : A critical discussion and case study
- 2017
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Ingår i: CIRED - Congrès International des Réseaux Electriques de Distribution, 2017.. - : Institution of Engineering and Technology. ; , s. 202-205
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Konferensbidrag (refereegranskat)abstract
- Over the past decade, the health index has become an increasingly popular asset management tool in utilities. The health index as a condition indicator can improve the decision making process. However, it also has challenges which need to be considered during development and implementation. This paper addresses the advantages and disadvantages of the health index as a condition indicator in a critical discussion. Moreover, a case study is presented where a health index is calculated for three transmission power transformers. The case study illustrates that age and the load factor included in the health index calculation lead to an immoderately high health index for the transformers T2 and T3. Thus, the paper ageing of the transformer windings are used instead which results in a plausible condition representation of all three transformers. The case study also demonstrates that the observation of condition trends over time is lost if the health index is transformed into a linguistic expression.
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| 2. |
- Jürgensen, Jan Henning, 1987-, et al.
(författare)
-
The Proportional Hazard Model and the Modelling of Recurrent Failure Data : Analysis of a Disconnector Population in Sweden
- 2017
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Ingår i: 2017 Cigré SC B3 (Substations) Colloquium, 18 - 20 September 2017, Recife, Brazil. ; , s. 1-8
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Konferensbidrag (refereegranskat)abstract
- Failure rate estimation is an important tool for planning and operating decision making in asset management of the power system. Moreover, the knowledge of how different explanatory variables impact the failure rate of the power system equipment is crucial for substation design. This study investigates 2191 work orders of 1626 non-current breaking disconnectors with 344 major failures. In particular, this paper analyses the disconnector failure data regarding recurrent failure data. Since the original PHM cannot handle recurrent event data, different extensions were developed such as the Andersen-Gill (AG), Prentice, Williams and Peterson (PWP), and the Wei, Lin, and Weissfeld (WLW) model. These models are applied to the disconnector dataset with 140 recurrent time-to-failure processes. The explanatory variables age at admission, remote control, preventive maintenance, and voltage level are assessed. The results show that preventive maintenance has a significant and positive impact on the recurrences with all tested methods. Also remote control, voltage level, and age are significant covariates. Compared to the single failure study previously conducted, where age had no significance, age is significant when assessing the recurrent failure which is the most critical difference to the analysis without recurrences.
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| 3. |
- Sadik, Diane-Perle, 1988-, et al.
(författare)
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Introduction of SiC MOSFETs in Converters based on Si IGBTs : A Reliability and Efficiency Analysis
- 2017
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Ingår i: 2017 IEEE 3rd International Future Energy Electronics Conference and ECCE Asia, IFEEC - ECCE Asia 2017. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509051571 ; , s. 1680-1685
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Konferensbidrag (refereegranskat)abstract
- Silicon Carbide (SiC) Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) have the potential to increase the power density in power electronics converters compared to the currently used silicon (Si). Their benefits are higher efficiency, higher switching speeds, and higher operating temperatures. Moreover, SiC MOSFETs, which are normally-off, offer the possibility to directly replace Si Isolated-Gate-BipolarTransistors (IGBTs) in already existing converter designs with minimal circuit changes. Nevertheless, as an emerging technology, the reliability performance remains to be investigated. A reliability analysis has been performed based on a full-bridge resonant converter rated at 60 kW for modern Electrostatic Precipitator (ESP) power supplies. This analysis shows that introducing SiC devices will increase the lifetime of the converter while reducing the losses. The investment costs of replacing the Si IGBTs with SiC MOSFETs can thus be covered with the reduction of the losses over the economical operational lifetime. Furthermore, a theoretical analysis on how introducing SiC MOSFETs could increase the power density of the converter while maintaining the efficiency and the reliability. Finally, an analysis on introducing redundancy as a way to improve the reliability of the system has been performed.
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