Paweł RÓZGA
Role of insulation coating in the mechanism of electric discharge development in transformer oil during lightning impulse
Energetyka 2009, nr 6 s. 335
Presented are results of tests concerning the role of paper insulation coating on HV electrode, in the mechanism of initiation and development of electric discharges in transformer oil. Tests were carried out in conditions of lightning voltage surge in a circuit of a non-uniform field, with an HV paper insulated electrode and a bare one having the same outer dimensions as the insulated electrode. Critically estimated are differences and similarities resulting from discharges measured parameters as well as from observation of oscillograms of the light emitted by discharge channels during their development.
Keywords: influence of insulation coating on electric discharge development, positive test lightning impulse, negative test circuit
Wojciech SIKORSKI, Krzysztof WALCZAK, Bolesław BRÓDKA, Hubert
MORAŃDA, Krzysztof SIODŁA, Hanna MOŚCICKA-GRZESIAK
Prototype acoustic emission method based system for on-line monitoring of partial discharges in power transformers
Energetyka 2009, nr 6 s. 340
Presented is a prototype on-line monitoring system for partial discharges (PD) in power transformers, based on acoustic emission method. Given is detailed description of the system architecture and the construction of its separate units. Realization and installation of the first prototype system, which is realized within the limits of 3-years' development research project, is the anticipated transformer monitoring system SYNIDS ES manufactured by MIKRONIKA.
Keywords: prototype system for on-line monitoring of partial discharges, acoustic emission transducers, measurement signals conditioning module, measurement signals acquisition module, expert system
Jerzy SKUBIS, Andrzej CICHOŃ, Sebastian BORUCKI
Acoustic emission based method of partial discharges evaluation as a component of a transformer insulation condition monitoring system
Energetyka 2009, nr 6 s. 346
Presented is a complex approach to diagnostics of power transformers under operational conditions, with special regard to partial discharges (PD) occurrence in their insulating systems. Attention is paid to problems relating to possibility of acoustic emission method (AE) application in transformers monitoring systems. Moreover, a review is made of quantities subject to control in monitoring systems as well as presented is an example of how an efficient PD detection and localization can be reached with the use of correlation
between DGA analysis results and AE method measurements.
Keywords: transformer supervision system, partial discharges, transformer insulation condition
Helena SŁOWIKOWSKA, Jerzy SŁOWIKOWSKI, Rafał ZALESKI
Role of furane compounds concentration measurements in assessment of heat processes occurring in cellulose insulation
Energetyka 2009, nr 6 s. 349
Discussed is the role, on the basis of specialized technical literature and the authors' own reasearch results, of furane compounds concentration measurements in oil samples drawn from working transformer, in the assessment of intensity and localization of local overheats in cellulose insulation.
Moreover, indicated is the role of a basic furane compound which is 2-furfural (2FAL) in assessment of paper turn insulation „wear-out" degree.
Keywords: furane compounds (2FAL), heat processes, transformer cellulose insulation
Jerzy SŁOWIKOWSKI
Influence of various factors on reliability of transformer oil sample breakdown voltage measurements
Energetyka 2009, nr 6 s. 353
There is proved that there is an influence, on the basis of Oommen's curves describing equilibrium between moisture content of the paper and water content of the oil as well as on the oil electric strength expressed as a function of water content calculated as a percentage of saturation, of transformer temperature (in the moment of sampling) on the measured oil breakdown voltage value.
Keywords: oil breakdown voltage measurements, Oommen's curves, paper-oil insulation system
Janusz SZCZECHOWSKI, Peter WERLE
Mobile High-Voltage Test System for on-site testing of power transformers
Energetyka 2009, nr 6 s. 355
ABB's latest development is a Mobile High-Voltage Test System for On-Site Testing of Power Transformers. Worldwide, it is the first 3-phase Mobile High-Voltage Test System for Power Transformers based on a static frequency converter which is especially designed for performing routine and special tests according to standards as IEC 60060-3, IEC 60076 and IEEE Std. C57.12.00. Supplemented by the most common diagnostic methods used under field conditions, the Mobile High-Voltage Test System enables ABB to offer a full range of testing on all types and brands of transformers from small grid transformers up to the largest step up generator transformers.
Keywords: power transformers, Mobile High-Voltage Test System
Marek SZROT, Janusz PŁOWUCHA, Jan SUBOCZ, Sebastian BORUCKI,
Andrzej CICHOŃ, Adam RZECZKOWSKI
TrafoGrade – transformer asset management system
Energetyka 2009, nr 6 s. 358
Presented is the TrafoGrade system which has been developed to support decisions to be taken in respect of power transformer operation. The system has been composed of four parts. The multi parametrical evaluation of a transformer technical condition is the most important element of the system. Evaluation of the importance index of a unit in the power system is additional information that complements the project. It is based on analysis of such factors as easiness of transformer exchange or repair and reliability or safety of the power supply.Another step is to determine perspectives of further operation of each unit separately, taking into consideration technical and economic aspects. Finally, results of analysis are put into a computer based management system which supports decisions to be taken in respect of transformer operation. Discussed is an example of the system implementation in one of the distribution companies in Poland.
Keywords: assessment, technical condition, operation planning, transformer, TrafoGrade system
Franciszek WITOS, Zbigniew GACEK
Characteristics of partial discharges (PD) generated by modelled sources immersed in transformer oil
Energetyka 2009, nr 6 s. 363
Presented is a measuring system for testing partial discharges with the use of calibrated acoustic emission method as well as analysis of test results of PDs, generated by modelled sources immersed in transformer oil. The modelled sources ensure observation of PDs occurring on the border between voltage electrode and transformer oil as well as inner discharges, surface discharges and discharges in oil. of the Mentioned types of discharges show different properties in the scope of time, discrimination threshold and time-frequency analysis. Results were related to other acoustic effects occurring in a working transformer.
Keywords: modelled PD sources, acoustic emission method, transformer oil
Rajmund WŁODARZ
Transformer cooling system control based on PLC controllers
Energetyka 2009, nr 6 s. 368
Described is the idea of using PLC devices in the control of a transformer cooling system. This solution allows to minimize number of elements in control box, what improves the reliability of all the system. Permanently increasing controllers performance makes it possible to realize better control algorithms. The controllers can also perform a lot of additional tasks, not directly connected with cooling process control. PLC controllers perfectly integrate with other transformer equipment, also on-line monitoring systems.
Keywords: radiator control system, PLC controller, transformers
Stefan WOLNY
Influence of transformer insulation system geometry on recovery voltage parameters
Energetyka 2009, nr 6 s. 370
Presented is investigation of the influence of a power transformer main insulation system geometry on recovery voltage selected parameters (diagnosis of paper-oil insulation condition with the use of RVM method). For this purpose, an X-Y type series-parallel substitute scheme is used, simulating the above mentioned paper-oil insulation system. Results of analyses are based on X-Y voltage response temporal characteristics obtained as a result of computer simulation of actuating the system with constant voltage. Investigations were carried out according to recommendations concerning RVM diagnosis of power units paper-oil insulation condition. Values of X-Y substitute scheme elements are selected in the way to possibly most precisely simulate the system of a big power transformer main paper-oil insulation. Analysed is influence of insulation system cumulative pressboard barriers and separators width on values of recovery voltage parameters obtained from the characteristics.
Keywords: X-Y substitute scheme, recovery voltage method (RVM), paperoil insulation system
Mikhail YARMARKIN
Service Experience with Polymeric Insulators in the South Karelia
Energetyka 2009, nr 6 s. 374
The technical observation of the outdoor polymeric insulators in some substations 35-110 kV in the South Karelia shows the abnormal high level of pollutions. The pollutants in the form of black spots overlay the main part of insulator surface. The microscope investigations of these pollutants detected its biological nature. It appeared that the pollutants are the microscopic fungus whose mycelium places on polymeric insulator surface. The article contains the recommendations for the future service of these polymeric insulators and for the design of new covering materials, protected from the biological attacks.
Keywords: polymeric insulators in the South Karelia, the pollutants
Marek ZENKER
Dielectric response of a transformer oil gap model with deposit layers on cellulose
Energetyka 2009, nr 6 s. 377
Described are measurements of relaxation phenomena in deposit layers on paper in a transformer oil gap. The research was conducted in the model of an oil gap. Measurements were taken in temperature of 230C and for various thicknesses of deposition. On the basis of curves analysis it was found that there were two relaxation phenomena and time constants were estimated for both. They showed that relaxation in these layers due to AC field may have, in specific conditions, influence on moisture contents estimation of an oil-paper insulation.
Keywords: oil gap, FDS, dielectric relaxation, deposition
Dariusz ZMARZŁY, Paweł AKSAMIT
Dielectric properties of fullerene doped transformer oils
Energetyka 2009, nr 6 s. 381
Analysed is the influence of nanoparticles addition on dielectric properties of a transformer oil. For the exemplary modification of the oil, fullerene C60 is used. Measured are electrical properties of mixtures: conductivity, permittivity, dielectric loss factor and breakdown voltage. It is observed that the C60 addition slightly influences breakdown voltage of mineral oil. Dielectric loss factor can be reduced twice dependently on nanoparticles concentration in oil. The resisitivity and permitivity do not change with the C60 content.
Keywords: transformer oil, dielectric loss factor, breakdown voltage, fullerenes, C60, nanomodifications
Bożena BORYCKA
Ecological aspects of fruit and vegetable waste biomass co-combustion with coal
Energetyka 2009, nr 6 s. 386
Presented are test results showing that all fruit and vegetable waste biomass compounds with coal emit less environment harmful susbstances than coal itself. We can therefore say that biomass sources can be „ecological additives" to conventional energy sources. Keywords: biomass and coal co-combustion, greenhouse gas emissions, ecological additives
Jerzy TRZESZCZYŃSKI, Wojciech MURZYNOWSKI
Management of a power installation elements individual durability
Energetyka 2009, nr 6 s. 391
Maintaining power installations in good technical condition means not only the assessment of their critical elements condition. Also the elements that influence reliability of such installation should undergo periodical diagnosis. Possession of a proper diagnostic system and a possibility to monitor working conditions through an adequate information system, enables us to obtain actual knowledge concerning technical condition of any number of elements and with minimum costs. The knowledge can be applied for optimization of range and time of repairs.
Keywords: technical condition of power installations, diagnostic systems
Wojciech BRUNNÉ
Diagnosis of fittings mounted on power pipelines
Energetyka 2009, nr 6 s. 394
The greater part of basic heat-mechanical equipment being at present in operation in electric power plants and CHPs, have already worked for more than 150 000 hrs while many have passed 200 000 hrs. Irrespective of the fact whether they work in block or collector systems, high-pressure and high-temperature power pipelines are a very important part of an electric energy source and their safe operation has essential influence on avalability of power installations. Discussed are causes of power pipelines fittings damages with special regard to technological defects (originating in icasting process) and wrong choice of fixings (designing faults).
Keywords: diagnosis of power pipelines fittings,technological defects, designing faults
Sławomir RAJCA
Influence of forgings quality on the life of long time operated rotors
Energetyka 2009, nr 6 s. 398
The majority of 25 MW and 250 MW turbines were installed in Poland in the years 1950 – 1960. So far, the rotors of turbines and generators have been in operation for 50–60 years what means for more than 300 000 hours. Metallurgical industry involved in production of rotor for gings in those years suffered from technological limitations connected with high quality ingots casting - it was difficult to ensure casting purity along the centre-line of a rotor. So, central bores in rotors were to be made to remove casting defects and examine forgings condition. Central bores improved quality of forgings but increased stress concentration on their surfaces. Described are defects detected on the surface of central bores in the final phase of rotors life as well as presented are examples of ineffective local chambering of the bores at that time.
Keywords: turbine rotors, central bores diagnostic tests