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ABSTRACT: Aus dem Forschungsbereich der isolierstoffe werden neue Technologien und Entwicklungen bei Hochspannungsisolationssystemen
beschrieben. Es werden jeweils feste, flüssige und gasförmige Isolierstoffe beschrieben und ihre Anwendung in der Energietechnik
diskutiert. Einen Technologiesprung stellen die keramischen Hochtemperatursupraleiter dar.
The research area of the insulating materials gives an insight into new technologies and developments for high voltage insulation
systems. Solid, liquid and gaseous insulants are picked out and their application in energy engineering is discussed. One
technology branch represents the ceramic high temperature superconductors.
e & i Elektrotechnik und Informationstechnik 05/2012; 119(5):153-157.
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ABSTRACT: In this paper the development of a tool for a fast and simple evaluation of the technical condition of electrical networks
will be presented. With this tool it is possible to compare different networks and network sections of different power suppliers
as well as utilities of the same voltage level or network sections of the same utilities. Whole networks, but also individual
components such as transformers and switchgears can be evaluated. An exact condition evaluation of networks represents a disproportionately
large expenditure of time. To get a fast overview over the technical condition of networks and electrical components the knowledge
of experts is necessary. The presented method takes into consideration both: expert knowledge as well as the consideration
of age, maintenance and operating loads of networks and their components. These aspects are included in reliability computation
mathematical functions which will be used in the developed technical condition evaluation tool. Beside the evaluation of the
technical condition the tool is based on the maintenance expenditure and the priority of the examined networks, too.
In dieser Arbeit wird ein Weg für eine rasche und einfache Evaluierung des technischen Zustands von elektrischen Verteilnetzen
aufgezeigt. Mit dem erstellten Werkzeug ist es möglich, verschiedene Netzwerke und Netzwerkabschnitte der gleichen Spannungsebenen
auch von unterschiedlichen Netzbetreibern miteinander zu vergleichen. Dabei können sowohl einzelne Komponenten wie zum Beispiel
Transformatoren, Kabel oder Schaltanlagen als auch ganze Netze evaluiert werden. Eine exakte Beurteilung des technischen Zustands
eines ganzen Netzwerks würde einen sehr großen Aufwand bedeuten. Um jedoch eine einfache und rasche Übersicht über den Zustand
eines Netzes und dessen Komponenten zu erhalten, wird auf Expertenwissen zurückgegriffen. Für die entwickelte und vorgestellte
Methode wurden Fachwissen des Betriebs- und Instandhaltungspersonals als auch Daten aus dem Netz wie zum Beispiel Betriebsmittelalter,
Betriebsbelastungen, Wartungs- und Instandhaltungstältigkeiten usw. zusammengeführt und entsprechend mathematisch aufgearbeitet.
Dies wurde in Folge in einem Bewertungswerkzeug für die Evaluierung des Zustands von elektrischen Netzen und Betriebsmitteln
eingesetzt.
e & i Elektrotechnik und Informationstechnik 04/2012; 120(12):446-450.
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ABSTRACT: Power transformers belong to the most important and most cost-intensive equipment of electrical power transmission and distribution.
If an error in a transformer occurs, this causes not only an interruption of the electrical power supply of far areas but
also large economic losses beyond that. Thus, the operation of transformers must guarantee a continuous and error free power
supply over decades. Occurring errors and thus self-announcing possible failures of transformers should be detected in time,
in order to initiate suitable measures for error correction. A continuous entry of the isolation status can prevent large
errors, extend service life of the system and optimize maintenance. Thus, apart from higher system availability an avoidance
of unplanned disconnections and expensive repairs are achieved. The emphasis of this contribution is to present methods which
permit a substantially more exact and more reliable predicate about the current status of the isolation system of liquid-isolated
power transformers.
Leistungstransformatoren zählen zu den wichtigsten und kostenintensivsten Betriebsmitteln der elektrischen Energieübertragung
und -verteilung. Ein Fehler in einem Transformator hat nicht nur den Stromausfall der angekoppelten Netzbereiche zur Folge,
sondern bringt auch wirtschaftliche Verluste mit sich. Der Einsatz von Transformatoren erfordert daher einen möglichst sicheren
und unterbrechungsfreien Betrieb über mehrere Jahrzehnte. Eintretende und sich ankündigende Fehler an Transformatoren sollten
rechtzeitig detektiert werden, um geeignete Maßnahmen zur Verhinderung oder die Behebung dergleichen einleiten zu können.
Eine kontinuierliche Erfassung der Isolationseigenschaften ermöglicht eine Vorbeugung langer fehlerbedingter Unterbrechungen
sowie eine Verlängerung der Wartungsintervalle und damit eine Optimierung der Instandhaltung. Abgesehen von der Erzielung
einer höheren Verfügbarkeit werden ungeplante Abschaltungen und teure Reparaturen verhindert. Der Schwerpunkt dieser Veröffentlichung
liegt in der Präsentation einer Methode, die auf dem Vergleich bekannter Maßnahmen der Zustandsbeurteilung basiert, welche
eine exaktere und wirtschaftlichere Aussage über den aktuellen Status des Isolationssystems von flüssiggekühlten Leistungstransformatoren
ermöglicht.
e & i Elektrotechnik und Informationstechnik 04/2012; 120(12):420-423.
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ABSTRACT: The reliability and operational risk of power transformers is strongly dependant on the condition of the electrical insulation system. Different kind of stress can be distinguished, normally a combination of electrical and thermal stress is present as well as the influence of humidity in the insulation system has to be considered. The so called multi-stress load results in an accelerated ageing process and the degradation of the insulation system. The condition of the mineral oil can be determined by sampling and analyzing the oil by the means of DGA and chemical-physical analysis. The solid insulation system mainly consists of transformerboard. The condition determination of the cellulose can be done by sampling, with is quite expensive and difficult. New dielectric methods which operate on the effect of response function have established in the last years. In this paper the focus should be directed on the mechanism of cellulose ageing and dielectric measurement.
Electrical Insulation (ISEI), Conference Record of the 2010 IEEE International Symposium on; 07/2010
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ABSTRACT: The innovative insulating tape for rotating machines shows advantages concerning the electrical and mechanical strength as well as its thickness and thermal conductivity. In this paper the new developed mica tapes should be tested with respect to the thermal behaviour of the end corona protection and voltage endurance of various types of used mica paper. For this reason a test series of different defined insulation systems was carried out to test the temperature rise and a long time test with increased voltage stress was applied. The results were evaluated within a statistical analysis and lifetime charts.
Electrical Machines, 2008. ICEM 2008. 18th International Conference on; 10/2008
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ABSTRACT: This study aims to gain insight into the consequences of local defects in stator winding insulation; therefore, optical (microscopic) inspections and voltage-endurance tests have been carried out on in-service aged generator bars. In this context, generator bars with mica-bitumen insulations and generator bars with mica-epoxy insulations were investigated. The mica-bitumen insulations had been in service for 43 years in a 12 kV hydro-generator. The generator bars with mica-epoxy insulation had been dismantled from two identically constructed 10.5-kV generators after 35 and 36 years of service. The time to breakdown values obtained from the voltage-endurance tests were evaluated using a Weibull distribution. Apart from the scale parameter, Weibull exponent of this distribution allowed for the identification of early failures. The voltage-endurance tests carried out on replacement bars for these generators did not yield any early failures; such failures, however, were detected on both types of the in-service aged insulations. In particular, these occurred at high levels of electric stress and at delaminations between the copper conductor and the groundwall insulation. It is concluded that the interpretation of the measured time to breakdown values and their scatter depends on the level of electric stress.
IEEE Transactions on Energy Conversion 04/2008; · 2.27 Impact Factor
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ABSTRACT: The suitability of an open-cell foam is investigated for the application as electric insulant in superconducting power equipment. The tested foam is made from melamine resin, a thermoset plastic from the aminoplastics group; it is a mechanical very flexible material with excellence compatibility to high and low temperature. The aim of these investigations was to test the aptitude of the liquid nitrogen impregnated open-cell foam with respect to the dielectric properties and the electric strength under different conditions. In this paper the results of permittivity measurements and ramp voltage tests are discussed and an outlook for future applications is given. The tests showed excellence mechanical and thermal characteristics for the application in LN2 vessels. The ACBV of the LN2 impregnated foam was 50 % less than the ACBV of pure LN2.
Journal of Physics Conference Series 07/2006; 43(1):767.
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ABSTRACT: The absorption of humidity in electric insulation systems is dominant for the behaviour of the insulation resistance and the breakdown strength. For this reason the dryness of the insulation system is tested as a routine test, e.g. the humidity of insulating oil at transformers. The dryness of generators is evaluated by measuring the time constant of the electric insulation. In an Austrian recommendation for the condition evaluation of rotating machines the humidity and insulation condition is evaluated by an empirical established dryness boarder. Since this evaluation method was recognized new insulation materials and production technologies for generator bars developed. This paper should give a view to the behaviour of the physical knowledge base of humidity absorption of solid insulation systems. The surface and volume resistance in dependence to temperature and air humidity for different insulation systems for rotating machines is measured and discussed
Properties and applications of Dielectric Materials, 2006. 8th International Conference on; 07/2006
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ABSTRACT: Taking a look at the structure of the hydro power plants of the Austrian utilities many of the electric machines are reaching a critical age. The risk of a failure or a break down can cause high financial consequences. For this reason a concept for the condition evaluation of hydro generators was developed. The focus of this procedure was to collect operational data; machine data and protocols of technical diagnosis measurements in order to form an objective analysis by weighing each factor. The aim was to make a kind of benchmark of all investigated machines. Several comparison charts were generated. This should result in making the right decisions about further operations, maintenance activities or replacement measures
Properties and applications of Dielectric Materials, 2006. 8th International Conference on; 07/2006
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ABSTRACT: Brazil's vast territory and huge forested regions have contributed to the widespread use of traditional crossarms made of native wood species in distribution lines. However, this situation is changing due to the increasingly high cost of native species and Brazil's environmental laws. In response to these changes, electric power suppliers have been seeking alternatives, and prototypes of reforested wood crossarms (such as Eucalyptus citriodora) impregnated with polymer (castor oil-based polyurethane resin) have been studied for application as mechanical supports for electrical power distribution systems, with very satisfactory results. This paper discusses mechanical and electrical tests conducted on this new material under critical conditions of temperature and relative air humidity. Also presented are the results of electrical tests conducted at Graz Technology University's Institute of High Voltage Engineering and System Management in Austria to analyze the material's insulation performance under electrical stress particularly under partial discharge during critical operating conditions.
Electrical Insulation Conference and Electrical Manufacturing Expo, 2005. Proceedings; 11/2005
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ABSTRACT: For the condition evaluation of the electric insulation systems, dielectric measurements are a very important tool for the diagnosis. Beside partial discharge and dissipation factor measurements the dielectric response of the electrical insulation system gives further information about the aging process and the condition of the insulation medium. The measurement and analysis of the polarization and depolarization current (PDC) is done according to the classical equivalent circuit of parallel and serial resistances and capacitances. This paper should give a view to PDC measurements at insulation systems for rotating machines.
Electrical Insulating Materials, 2005. (ISEIM 2005). Proceedings of 2005 International Symposium on; 07/2005
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ABSTRACT: The objective of this paper is the scientific investigation of the electrical long-time response of XLPE-insulation. The electrical XLPE-insulation system is susceptible to aging when subjected to the thermal, electrical, environmental and mechanical stresses experienced under service conditions. Based on extensive experimental research work concerning the breakdown behaviour of XLPE, it is shown in this paper that beyond the statistical history, space charge processes contribute to the AC dielectric strength decrease of thick-walled XLPE-insulation. Values for the AC breakdown strength from long time tests on a cable model and 2 real cables are given and an example for calculation with approximation methods, to compare the values, is carried out. Weibull statistical analysis of area and volume effects on the breakdown strength in XLPE, for a coaxial cylindrical electrode configuration, is examined.
Electrical Insulation and Dielectric Phenomena, 2004. CEIDP '04. 2004 Annual Report Conference on; 11/2004
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ABSTRACT: For the operation of high temperature superconducting (HTS) devices it is necessary to cool the HTS conductor down to the operating temperature of about 77 K. Depending on the application warm or cold dielectric insulation systems are used in electrical power systems and high voltage apparatus. Liquid nitrogen (LN<sub>2</sub>) is an excellent dielectric liquid, but there is less knowledge about the quality criterions and their measuring methods. For the measurement of dielectric parameters (e.g. breakdown voltage, partial discharge, relative permittivity) the classical measuring methods have to be adapted. This paper gives a view to the results of dielectric measuring methods with LN<sub>2</sub>. The measurements were done with different degrees of LN<sub>2</sub> pureness.
Properties and Applications of Dielectric Materials, 2003. Proceedings of the 7th International Conference on; 07/2003
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ABSTRACT: For the operation of high temperature superconducting (HTS) devices liquid nitrogen (LN2) is necessary to cool the HTS conductor down to the operating temperature of about 77 K. Depending on the application in electrical power systems and high voltage devices, LN2 is also an attractive dielectric liquid. Some prototypes of cables, power and traction transformers and current limiters were built, but there is not sufficient knowledge about optimum dielectric structures and ageing. The aim for the measurements is to test different electrical insulating structures in specified LN2 at AC, DC and impulse voltages and to observe the partial discharge behaviour, breakdown voltage and ageing.
Dielectric Liquids, 2002. ICDL 2002. Proceedings of 2002 IEEE 14th International Conference on; 02/2002
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ABSTRACT: Since the development of flexible high temperature superconducting multifilament wires superconductive coils were constructed for the application in electric power equipment. The dielectric behaviour of conventional technology is well known, but this experience can only be partially applied to superconducting insulation systems. Some prototypes of cables, power and traction transformers and current limiters were built, but there is not sufficient knowledge about optimum dielectric structures and ageing. This paper gives a view to the criterions for liquid nitrogen as coolant and insulating medium of low temperature insulating systems for electric power equipment and shows the results of dielectric measurements tested with different structures.
Physica C: Superconductivity.
