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eng Power transformer lifecycle: Transformer specification and sustainability
Wetzer, Jos
Transformers Magazine Vol. 4, No. 1, 2017
To secure the quality of the installed asset base, in this case power transformers, utilities and industries rely on quality assurance. This paper will focus on quality assurance in the early phases of the lifecycle, prior to operation. Elements contributing to this quality assurance are specification, design review, quality review of the manufacturer or production, and testing. The question will be addressed what quality assurance options are available and meaningful. Moreover, the paper presents specification as one of the possibilities of qu...
Hrčak ID: 202377


eng A century of dissolved gas analysis - Part II
Grisaru, Marius
Transformers Magazine Vol. 6, No. 4, 2019
Future brings some changes to DGA. It is expected that offline DGA in standard laboratories will gradually disappear as a routine test and transformers without online DGA will be tested by using simple portable devices. The online sensors will be monitored from a central control room with a sophisticated artificial intelligence in an effort to predict failures.
Hrčak ID: 226061


eng A century of dissolved gas analysis - part III
Grisaru, Marius
Transformers Magazine Vol. 7, No. 1, 2020
With time, the size of the transformer increased exponentially both in power andvoltage. Although huge improvements have been made regarding the magnetic core and the decrease of core losses, a transformer is now producing much more heat due to the design optimization and size reduction. Heat reduces the insulating properties of the insulating matrix, reducing the conducting properties and accelerating all chemical reactions including ageing and corrosion. The stresses from the insulation materials increase gradually. In the last century, th...
Hrčak ID: 232078


eng Fire testing for transformer pit fire protection
Lindström, Johan; Försth, Michael
Transformers Magazine Vol. 1, No. 3, 2014
Transformer pits are conventionally filled with rocks in order to achieve passive fire safety in the event of an oil leak from the transformer. Other solutions also exist but there is no well defined test method that allows an assessment of the fire performance. In this brief article, such a test is presented together with test results for an alternative system where profile planks are used instead of rocks.
Hrčak ID: 185466


eng Europe, North America and China: The future and is Brexit at all relevant
Aubertin, Steve
Transformers Magazine Vol. 4, No. 2, 2017
There are very few similarities between transformer markets in Europe, North America and China; however, together these account for 64 % of the global transformer market. Analysis of imports and exports of these individual markets reveals their nature and the bonds among them, and in the end, leads to a somewhat surprising conclusion.
Hrčak ID: 202381


eng The measurement and normalisation of dielectric dissipation factor for diagnostics of transformer insulation
Shkolnik, Anatoly
Transformers Magazine Vol. 2, No. 4, 2015
This article describes additional features of the method of Dielectric Dissipation Factor (DDF)/Tangent Delta (tgδ) measurement for a more accurate diagnosis of the condition of the transformer solid insulation. The proposed method is based on determining the DDF weight of solid insulation and oil in the measured value of DDF for the proper insulation zone of the transformer. The article proposes normalisation of DDF values according to the rated voltage of the transformer, and the analysis of the impact of design combining insulation and its c...
Hrčak ID: 181969


eng Transformer bushings and oil leaks: A cost effective way to address oil and nitrogen leaks
Wickman, Steven H.
Transformers Magazine Vol. 4, No. 5, 2017
Many oil-filled large power transformers have been in service for years. One issue with aging transformers is addressing oil leaks. This article describes a cost-effective technique for repairing these oil leaks. Repairs can be made without draining the oil, or removing bushings. Often the repairs can be made with the transformer in service. This article presents the techniques used by a company that has been performing leak repairs on electric substation equipment since 1988, and works exclusively on electric substation equipment.
Hrčak ID: 202530


eng Tap-changer know-how: Hermetical sealing of transformers and tap-changers
Frotscher, Rainer
Transformers Magazine Vol. 4, No. 1, 2017
Oil-filled electrical apparatus must be able to handle a certain thermal expansion of the oil, which is caused by varying oil temperatures due to load changes and/or fluctuations in ambient temperature. This article provides an overview of sealing methods for transformers and tap-changers, discussing also appropriate tap-changer protection techniques.
Hrčak ID: 172546


eng Transformer market development: Demand and supply - Are they ever in balance
Aubertin, Steve
Transformers Magazine Vol. 4, No. 1, 2017
This article brings a historical overview of transformers market development, which not only reveals why there have been so many mergers, acquisitions and failures among the manufacturers over the years, but also presents the changing patterns noticeable in global demand for transformers, which are of critical importance for each market player.
Hrčak ID: 202374


eng Reactor-type tap changers testing
Levi, Raka; Milojević, Goran; Osmanbašić, Edis
Transformers Magazine Vol. 4, No. 1, 2017
This paper discusses DVtest or Dynamic Resistance Measurement, a new diagnostic method used in detecting on load tap changer (OLTC) operational problems, as applied to reactor-type tap changers. Several cases of tap changer problems are presented, which were detected using the DVtest method – a high speed recording of a DC test current as the OLTC goes from tap to tap. The focus of the article is on the reactor-type tap changers. These reactor OLTC constructions apply Preventive Autotransformers (PA) for current control instead of resistors. Sp...
Hrčak ID: 202379