Post-irradiation effect analysis on XLPE-insulated LV cables used in nuclear power plants

This paper investigates aging of low voltage cables used in nuclear power plants by the means of the dielectric spectroscopy technique. Aging has been performed on XLPE cables through high temperature and different dose rates in order to evaluate the electrical response under different aging conditions. Test have been carried out immediately after aging and years after the radiation source has been turned off. Significant changes in dielectric response have been observed due to postirradiation effects, suggesting that degradation continues even after the aging source has been removed

Space charge and dielectric response measurements to assess insulation aging of low-voltage cables used in nuclear power plants

The current design life of nuclear power plant (NPP) could potentially be extended to 80 years. During this extended plant life, all safety and operationally relevant Instrumentation & Control (I&C) systems are required to meet their designed performance requirements to ensure safe and reliable operation of the NPP, both during normal operation and subsequent to design base events. This in turn requires an adequate and documented qualification and aging management program. It is known that electrical insulation of I&C cables used in safety related circuits can degrade during their life, due to the aging effect of environmental stresses, such as temperature, radiation, vibration, etc., particularly if located in the containment area of the NPP. Thus several condition monitoring techniques are required to assess the state of the insulation. Such techniques can be used to establish a residual lifetime, based on the relationship between condition indicators and ageing stresses, hence, to support a preventive and effective maintenance program. The object of this thesis is to investigate potential electrical aging indicators (diagnostic markers) testing various I&C cable insulations subjected to an accelerated multi-stress (thermal and radiation) aging

State of the Art Review of High Voltage Insulation Monitoring

The devastating effects of global warming and climate change are now well understood and there is broad unity that fundamental changes are needed. This is clearly addressed in the United Nations Sustainable Development Goals. The main perpetrator contributing to global warming and climate change is how we consume energy, which will need to transition from fossil fuels to renewable energy. The mass integration of renewable energy sources aimed to mitigate the effects of global warming, will greatly alter how we generate, transmit and consume energy. If we combine this with the large shift in load consumption, due to the integration of electrical vehicles, there is no doubt that the electrical transmission system will be subjected to major changes in future decades. The existing transmission grid is an aged and mature system, with large parts being installed all the way back in 60s and 70s, thus nearing the end of service. The existing grid has continuous performance issues and the knowledge on fault and ageing mechanisms are still insufficient. A thorough assessment of the current state of the grid is necessary in order to properly gauge its ability to cope with mass integration of HV systems, predominantly HVDC. A key part in assessing the current state of the grid while simultaneously increase its resilience is the utilization of high voltage monitoring methods, as they are key to prevent and predict transmission faults. Due to the increased requirement of long distance high capacity transmission, especially in submarine conditions, the knowledge and monitoring of cables will be of high importance. Compared to AC technology, DC have been regarded as niche and specialist field, thus have been allocated far less attention and research, hence the knowledge and technology of DC is still limited. This thesis will assess the state of the art of high voltage monitoring while simultaneously explore its role towards achieving the UN Sustainable Development Goals. Keywords: UN Sustainability Goals, Partial Discharges, Tan Delta, SF6, XLPE, High Voltage MonitoringMasteroppgave i energiENERGI399MAMN-ENER

Time domain analysis of switching transient fields in high voltage substations

Switching operations of circuit breakers and disconnect switches generate transient currents propagating along the substation busbars. At the moment of switching, the busbars temporarily acts as antennae radiating transient electromagnetic fields within the substations. The radiated fields may interfere and disrupt normal operations of electronic equipment used within the substation for measurement, control and communication purposes. Hence there is the need to fully characterise the substation electromagnetic environment as early as the design stage of substation planning and operation to ensure safe operations of the electronic equipment. This paper deals with the computation of transient electromagnetic fields due to switching within a high voltage air-insulated substation (AIS) using the finite difference time domain (FDTD) metho

Conceptual Design of High Temperature Superconducting Toroidal Field Coils for Future Fusion Power Plants

Aus der langjährigen Forschung im Bereich der magnetischen Eingrenzung sind Stellaratoren und Tokamaks entstanden, die starken und ungleichmäßigen Magnetfelder zum Einfangen der Plasmapartikel nutzen und es ihnen ermöglichen, sich frei auf bestimmten Wegen zu bewegen. Die Tokamaks haben durch ein einfacheres Spulendesign, verschachtelte magnetische Oberflächen und die Fähigkeit, mit positiver magnetischer Scherung zu arbeiten, an Bedeutung gewonnen. Derzeit plant die Europäische Union (EU), ihre Studien über Tokamak auf Demonstrationskraftwerke (EU-DEMO) auszudehnen, der Strom erzeugen können. Ziel dieser Studie ist es, ein Konzept für die Ringkernfeldspule (TF-Spule) für zukünftige Kraftwerke mit dem Systemcode PROCESS zu entwickeln. Ziel dieser Studie ist es, ein Konzept für die Toroidalfeldspule (TF-Spule) für zukünftige Kraftwerke mit dem Systemcode PROCESS zu entwickeln. Der PROZESS-Code gibt bestimmte Informationen wie die ungefähre Form der TF-Spule, die Fläche des Wickelpakets, das Magnetfeld an der Plasmaachse. Ausgehend vom Eingang wird das Wickelpaket der TF-Spule entworfen. Zum Beispiel, wenn die Pancake-Wicklung gegenüber der Lagen-Wicklung bevorzugt wird. Zum Beispiel, wenn die Pancake-Wicklung gegenüber der Lagen-Wicklung bevorzugt wird. Die erste Lage, die der Plasmawärme zugewandt ist, wird angesammelt, da sie sich im Hochfeldbereich befindet, wodurch der Magnet mit einer geringeren Betriebsmarge arbeitet. Der Leiter der Pancake-Wicklung ist jedoch in Umfangsrichtung und nicht entlang der Achse eines Magneten gewickelt und jedes Modul ist separat gewickelt und elektrisch in Reihe geschaltet. Der wesentliche Vorteil bei diesem Verfahren ist, dass die Temperatur im Hochfeldbereich am niedrigsten ist, da sich der Heliumeinlass im Hochfeldbereich des Wickelpakets und der Auslass im Niederfeldbereich befindet. Das Wicklungspaket mit der elektrischen Schaltung ist in Reihe geschaltet und die hydraulische Schaltung ist parallel geschaltet. Aus dem PROZESS-Code wird überprüft, ob das Magnetfeld an der Plasmaachse gleich dem erforderlichen Magnetfeld ist. Das Spitzenmagnetfeld wird auch zur Bestimmung des Arbeitspunktes des Leiters berechnet. Die 3D Elektromagnetische Simulation wird mit dem Präprozessor TOKEF und dem Code EFFI durchgeführt. Codes zur Magnetfeldberechnung einer allgemeinen dreidimensionalen Stromverteilung, die Formulierungen verwenden, die auf einer fadenförmigen Annäherung und der endlichen Leitergröße basieren. Diese Codes werden durch eine Reihe von verteilten Filamenten unter Verwendung der EFFI-Formel, die aus dem Bio-Savart Gesetz für die Volumenstromverteilung abgeleitet wurde, approximiert. Die Statik der TF-Spule bestimmt die Spannungen im Spulengehäuse und im Wickelpaket. Der Bereich mit den höchsten Spannungen liegt in der Mittelebene des inneren Schenkels, was durch eine ähnliche Analyse mit dem Spulenmagnetsystem JT-60SA TF bestätigt wird. In der EU DEMO führt die TF-Spule hohe Ströme (in MA) und erzeugt hohe Felder. Die TF-Spule ist daher hohen magnetischen Drücken und Kräften ausgesetzt. Um die Spannungen im Wickelpaket und am Gehäuse zu untersuchen, werden in COMSOL und ANSYS verschiedene Methoden zur Analyse der Spannungen am Gehäuse, des Lösens des Wickelpakets und der Spannungen in Isolationsbauteilen betrachtet. Ein wichtiger Fehler, der bei der Konstruktion supraleitender Magnete zu berücksichtigen ist, ist der Übergang von der supraleitenden zur normal leitenden Phase, dem sogenannten Quench. Da im normal leitenden Modus der elektrische Widerstand des Supraleitermaterials hoch ist, erzeugt die Einführung von Kupfer als elektrischer Ableiter für den Stromfluss eine Joule-Erwärmung. Der Magnet muss durch Anschluss eines externen Widerstandes parallel zum Magneten entladen werden, um einen übermäßigen Temperaturanstieg zu vermeiden. Die maximal zulässige adiabatische Hotspot-Temperatur, wie sie vom International Thermonuclear Experimental Reactor (ITER) festgelegt wurde, ist auf 150 K begrenzt, wobei alle Materialien im Leiter berücksichtigt werden, d.h. Supraleiter, Kupfer, Helium, Edelstahlmantel und Isolierung. Um die Quenchausbreitung zu simulieren, wird eine externe Heizung in den Supraleiter eingesetzt und überprüft, wie die Ausbreitung ist und welche maximale Temperatur sie während der Entladungszeit erreicht

Technical Design Report for the PANDA Solenoid and Dipole Spectrometer Magnets

This document is the Technical Design Report covering the two large spectrometer magnets of the PANDA detector set-up. It shows the conceptual design of the magnets and their anticipated performance. It precedes the tender and procurement of the magnets and, hence, is subject to possible modifications arising during this process.Comment: 10 pages, 14MB, accepted by FAIR STI in May 2009, editors: Inti Lehmann (chair), Andrea Bersani, Yuri Lobanov, Jost Luehning, Jerzy Smyrski, Technical Coordiantor: Lars Schmitt, Bernd Lewandowski (deputy), Spokespersons: Ulrich Wiedner, Paola Gianotti (deputy

Technical Design Report for the PANDA Solenoid and Dipole Spectrometer Magnets

This document is the Technical Design Report covering the two large spectrometer magnets of the PANDA detector set-up. It shows the conceptual design of the magnets and their anticipated performance. It precedes the tender and procurement of the magnets and, hence, is subject to possible modifications arising during this process

Dielectric Spectroscopy as a Condition Monitoring Technique for Low-Voltage Cables: Onsite Aging Assessment and Sensitivity Analyses

open3siThis work presents the development, validation, and sensitivity analyses of a portable device capable of performing high-frequency dielectric spectroscopy tests on site. After a brief introduction on the operation principle and the description of the impact of frequency on dielectric spectroscopy, the article presents the results of tests on reference samples confirming good agreement with expected values. The frequency region in which the device operates, 1–200 kHz, was chosen because of its correlation with oxidative species of polymeric compound. The sensitivity analyses were performed measuring the dielectric response of low voltage cables with different aged lengths. The outcome of these tests is twofold. On the one hand, they confirm the suitability of the technique for aging evaluation, and, on the other hand, they allow the assessment of the minimum aged length (damage ratio) which causes appreciable variations on the obtained dielectric spectrum. This quantity was found to be ~35% of the total cable length.openSuraci S.V.; Li C.; Fabiani D.Suraci S.V.; Li C.; Fabiani D

Decision-Making for Utility Scale Photovoltaic Systems: Probabilistic Risk Assessment Models for Corrosion of Structural Elements and a Material Selection Approach for Polymeric Components

abstract: The solar energy sector has been growing rapidly over the past decade. Growth in renewable electricity generation using photovoltaic (PV) systems is accompanied by an increased awareness of the fault conditions developing during the operational lifetime of these systems. While the annual energy losses caused by faults in PV systems could reach up to 18.9% of their total capacity, emerging technologies and models are driving for greater efficiency to assure the reliability of a product under its actual application. The objectives of this dissertation consist of (1) reviewing the state of the art and practice of prognostics and health management for the Direct Current (DC) side of photovoltaic systems; (2) assessing the corrosion of the driven posts supporting PV structures in utility scale plants; and (3) assessing the probabilistic risk associated with the failure of polymeric materials that are used in tracker and fixed tilt systems. As photovoltaic systems age under relatively harsh and changing environmental conditions, several potential fault conditions can develop during the operational lifetime including corrosion of supporting structures and failures of polymeric materials. The ability to accurately predict the remaining useful life of photovoltaic systems is critical for plants ‘continuous operation. This research contributes to the body of knowledge of PV systems reliability by: (1) developing a meta-model of the expected service life of mounting structures; (2) creating decision frameworks and tools to support practitioners in mitigating risks; (3) and supporting material selection for fielded and future photovoltaic systems. The newly developed frameworks were validated by a global solar company.Dissertation/ThesisDoctoral Dissertation Civil and Environmental Engineering 201