Szymon BANASZAK
Analysis of transformer winding deformation with the application of frequency response analysis (FRA) method
Energetyka 2009, nr 5, s. 276
In recent years the average age of power transformers is constantly growing. Therefore it is important to conduct their thorough diagnostics to obtain information on their technical condition and to plan their repairs. An intensively developed diagnostic methods is frequency response analysis (FRA) used for assessment of windings' mechanical condition. One of directions in FRA research is computer modelling of real objects. Presented is a comparison of such objects with their models. Although the model was based on simplified geometrical data of windings and consisted of reduced number of elements it was possible to get FRA curve comparable to measured data.
Keywords: method of frequency response analysis (FRA) of windings, transformer winding deformation
Tomasz BOCZAR, Sebastian BORUCKI, Andrzej CICHOŃ
Partial discharge patterns measured with the application of acoustic emission method
Energetyka 2009, nr 5, p. 278
Discussed is characteristics of the base of knowledge consisting of reference patterns and elaborated for the basic forms of partial discharges, measured with the use of acoustic emission method (AE). The created base contains catalogued, multi-parametric groups of descriptors characterizing the AE signals which, under the precisely determined meteorological conditions, enable recognition of PDP basic forms. Presented is a „fingerprint" of acoustic emission signals generated by partial discharges in an oilimmersed blade-to-blade type system
Keywords: partial discharge patterns, acoustic emission method, oil-immersed blade-toblade system
Gustav CSEPES, Jan SUBOCZ
Corrosive sulphur – detection and prevention methods
Energetyka 2009, nr 5, p. 283
Discussed are methods for detecting corrosive sulphur in paper-oil insulation of transformers. Presented are results of the methods' efficiency comparison tests concerning identification of corrosive and potentially corrosive sulphur. On the basis of it, we can come to a conclusion that in general sensitivity of new methods is better than of the previous ones. But no correlation between them was observed and, what is more, non-corrosive oils according to one standard can show corrosive properties in tests based on some other standards. This in turn shows that practically every method carries out its own, subjective evaluation of this phenomenon. Given are also basic informations concerning copper passivation as a method to prevent sulphur corrosion.
Keywords: corrosive sulphur in paper-oil transformer insulation, copper passivation
Gustav CSEPES, Jan SUBOCZ
Oil corrosivity and Cu2S deposition in power transformers
Energetyka 2009, nr 5, p. 288
Discussed is the problem of sulphur corrosion in paper-oil transformer insulation. Indicated are sulphur sources in transformer oil as well as causes and effects of copper sulfides deposition on insulation paper and copper. Discussed is influence of transformer working temperature and type of oil as well as assignment and construction of a transformer on the process of copper sulfides formation. It is an important conclusion that oil always contains traceable amounts of sulphur compounds which presence is indispensable for obtaining proper stability of oxidation. On the other hand, the problem of corrosive or non-corosive behaviour of sulphur compounds depends largely on a transformer working conditions and type of oil.
Keywords: oil corrosivity, Cu2S deposition, power transformers
Grzegorz GALOWY, Marek KUBISTA
Innovative technology in preventing and fighting fire hazards
Energetyka 2009, nr 5, p. 293
Discussed are innovative solutions in the field of preventing the fires to start and expand and possibilities to extinguish them. Presented is construction and operation principle of a dry powder fire extinguishing ball as well as characterized are its basic parameters and testing results. Shown is its automatic deployment and methods for manual use. Emphasized is positive influence of this technology on natural environment. Described is wide spectrum of applications and perspectives of further development.
Keywords: dry powder fire extinguishing ball, fire hazards
Jarosław GIELNIAK, Andrzej GRACZKOWSKI, Hubert MORAŃDA, Krzysztof WALCZAK,
Piotr PRZYBYŁEK, Bolesław BRÓDKA, Hanna MOŚCICKA-GRZESIAK
Calibration of measuring systems for moisture content determination in paper-oil
transformer insulation based on polarization methods RVM and FDS
Energetyka 2009, nr 5, p. 293
Discussed is a problem of calibration of measuring systems for moisture content determination in cellulose insulation of the transformer by means of polarization methods. Presented are available referential methods, also a new analysis method based on spectrophotometery in the near infrared worked out by the authors. Indirect methods, of which the correctness was verified, are a frequency dielectric spectroscopy (FDS) and a method of return voltage measurement (RVM). A calibration procedure included research on samples and simple models, however the verification was carried out on real transformers subject to renovation. Tests confirmed the great reliability of tested methods.
Keywords: Karl Fischer titration, near-infrared (NIR) spectrophotometric method, calibration of systems for transformer insulation moisture content determination, FDS method, RVM method
Michael KRÜGER, Maik KOCH, Alexander KRAETGE, Kay RETHMEIER
Diagnostic Measurements on Power Transformers
Energetyka 2009, nr 5, p. 299
Power transformers are critical, capital-intensive assets for utilities and industry. Transformers are extremely reliable; however, many of the transformers in use today have already exceeded their design life. Today transformers are not automatically replaced, if they have reached the end of their life span, but left in service as long as possible. In contradiction to the past power transformers are operated nowadays at or above rated power. This accelerates the ageing process of the inner insulation, particularly of the insulation paper, which cannot be easily replaced. Investments of new transformers have to be planned in advance because big transformers cannot be bought ready made from the factory. For a systematic replacement and to avoid unexpected breakdowns diagnostic tools are more and more important. Reliable assessment of the ageing state of high voltage power transformers is a basic condition for a failsafe and cost-saving service. One ageing indicator is the water content in the solid part of the insulation (paper, pressboard). Water is an ageing product and accelerates the further deterioration of cellulose through de-polymerization. In addition increased water content in oil may cause bubble formation and lead to an electrical breakdown. It is important to have reliable tools for measuring the water content in the oil-paper-insulation. This way unexpected breakdowns can be avoided and the maintenance, repair or replacement can be scheduled in time.
Additional diagnosis tools are necessary for locating faults to avoid unexpected complete breakdowns and enable repair and maintenance work before it is too late. Those faults are often indicated by the oil analysis, which is a proved and meaningful tool. The paper gives an overview about the latest measuring technologies and contains interesting case studies for successful insulation diagnosis and fault locations in power transformers.
Keywords: water content in paper insulation, water content in transformer oil, bubble formation, oil analysis, power transformers
Alexander MONASTYRSKIY
Main methods and measurement instrumentation for big power transformers diagnostics
Energetyka 2009, nr 5, p. 305
In Russia power equipment with service life more than designed reaches 75%. The control parameters, measuring devices and methods of obtained results interpretation are indispensable to successful solving problem of diagnostic. The paper presents system of on-line monitoring for HV power transformers – SCIT, designed by experts of Sant- Petersburg state polytechnic university. It is based on measurement of concentration of gasses dissolved in oil, humidity of solid insulation, concentration of mechanical impurities in oil, electric performances of the basic bushing insulation and performances of partial discharges (PD). Proper methods of diagnostics for each type of measurement are also presented.
Keywords: system of on-line monitoring for HV power transformers, transformers
Bruce PAHLAVANPOUR
Monitoring the condition of oil-filled bushings by using Dissolved Gas Analysis
Energetyka 2009, nr 5, p. 308
Statistics have proved that 30% of transformer failures are related to bushing malfunctions.
Described are problems connected with monitoring of bushings condition. Comparison is made between intrusive and non-intrusive tests. Given is general description of dissolved gas analysis. Shown are examples of faults typically occurring in bushings, which can be determined by interpretation of measurement results of some key gases concentrations and ratios, obtained with the use of DGA method. Presented is the Duval triangle with the method of calculation and interpretation of results. Discussed are actions which can be taken dependently on DGA results. Mentioned is also the problem concerning ambiguity of DGA method – for instance, generation of hydrogen can sometimes be caused not by electrical faults but by influence of some construction material on the oil, but still Dissolved Gas Analysis (DGA) is a powerful tool for monitoring the condition of oil-filled equipment and its application can possibly prevent catastrophic failures.
Keywords: transformer failures, oil-filled bushings monitoring, Dissolved Gas Analysis (DGA), gas concentration, gas ratio, Duval triangle
Jadwiga PEWCA, Władysław PEWCA
Selected problems of power transformers acceptance tests
Energetyka 2009, nr 5, p. 311
An attempt is made to clarify the most essential and selected problems connected with acceptance tests to the users, being at the same time the customers for ordered new, or repaired, power transformers,. All problems connected with an issue are comprised in a book „Acceptance tests of transformers". Special attention is paid to tests which, in the light of the at present obligatory standards, can be (according to European standards) a novelty for a user – also in the aspect of necessary assignments made with a producer during contracting a new transformer or a transformer's modernization or repair. Indicated are these elements of tests which are sometimes realized incorrectly, often unknowingly accepted by customers.
Keywords: power transformers, acceptance tests, selection tests, type tests, special tests
Piotr PRZYBYŁEK, Hubert MORAŃDA, Hanna MOŚCICKA-GRZESIAK
„Bubble effect" in conditions of new and highly degraded paper-oil insulation
Energetyka 2009, nr 5, p. 319
Discussed is a dangerous for transformers effect of steam liberation from cellulose insulation called „bubble effect". Indicated are factors influencing the initiation temperature of this effect. Presented are test results of „bubble effect" initiation temperature in function of water content in paper insulation. Tests were made of a new paper and a highly degraded one. Given are formulae describing initiation temperature of the „bubble effect" under assumed experimental conditions.
Keywords: „bubble effect", paper-oil insulation, transformer
Janusz ROPA, Czesław KARWAT
Ecological Aspects of the MV/LV Transformer Substation Operation
Energetyka 2009, nr 5, p. 322
Environment protection is a very important question that also concerns operation of transformer substations. There is a set of standards and regulations that determine ecological requirements to be met by transformer substations and they apply to the casing protection degree, substation casing resistance to mechanical damage, arc protection, fire precautions as well as emissions of electromagnetic field and noise. Transformer substations should be adequately tested and the testing results should be supported by the Certificate of Conformity.
Keywords: ecology, transformer substation, environment protection requirements, Certificate of Conformity