1,720,970 research outputs found
Health index: The TERNA's practical approach for transformers fleet management
No full textThe asset management of any Transmission System Operator (TSO) cannot ignore the evaluation of the power transformers fleet. Even in the absence, to date, of any specific international guide or standard, every big electrical utility is adopting a home-made 'Health Index'. An HI is developed to summarize in numerical form the transformers' reliability for the purpose of evaluation, ranking and comparison. In the present paper the author will elucidate a new model that merge the evidences of periodic tests (DGA, furans, acidity, inductance, FDS, etc.) with the keraunic properties of a substation
Corrosive sulphur in mineral oils: its detection and correlated transformer failures
No full textThe presence of corrosive sulphur in current insulating oils is discussed and typical winding failures in transformers and shunt reactors, due to the resultant formation of copper sulphide films and particulate matter, are described. Different standard test methods for the detection of corrosive sulphur in oils are compared and ASTM D1275 is shown to be the most sensitive
Corrosive Sulfur Induced Failures in Oil-Filled Electrical Power Transformers and Shunt Reactors
No full textThe nature and causes of corrosive sulfur induced failures are examined in oil-filled transformers and shunt reactors. Copper sulfide, which is formed when the corrosive sulfur in a mineral oil reacts with the copper conductors, is likely to diffuse into the paper tapes insulating the conductors. Since copper sulfide is partially conducting, the dielectric losses of the contaminated oil-impregnated-paper tapes are markedly increased; paper tapes in close proximity to the copper conductors are found to attain tan delta values > 1.0 even at room temperature. It is highly likely that thermal instabilities develop at those sites at operating temperatures, leading to increased loss currents and, ultimately, short circuits between the turns. This sequence of events is substantiated by evidence from the field, which indicates large areas of thermally degraded insulations and charred breakdown regions along the coils, the extent of which becomes more pronounced at higher operating temperatures (toward the top of the windings)
In Service Reduction of Corrosive Sulfur Compounds in Insulating Mineral Oils
No full textRemoval of dibenzyl-disulfide (DBDS) from a mineral oil of an in-service transformer was found to greatly reduce the overall corrosive sulfur content of the oil. In addition, a very significant improvement was also obtained in the acidity, surface tension, and to some degree in the dielectric loss characteristics of the mineral oil
Effects of Metal Deactivator Concentration upon the Gassing Characteristics of Transformer Oils
No full textRecent years have witnessed a relatively large number of power transformer and shunt reactor failures, which were attributed to the presence of corrosive sulfur compounds in the insulating oils and their attending reactions with copper to form electrically conductive copper sulphides. The associated problems appeared to be initially resolved by the addition to the insulating oil small amounts of a metal deactivator (more commonly called passivator), a derivative of 1,2,3 benzotriazole (BTA). However, over the past four years, additional problems arose that were principally associated with the evolution of gases from the electrical insulating oils, containing the metal deactivator. These observations, recorded in the field as well as reproduced in laboratories, are examined in this paper
Transformers Surveillance Following Corrosive Sulfur Remedial Procedures
No full textOver the last decade, dibenzyl-disulphide was found to be present in a large number of mineral insulating oils. This sulfur compound tends to react with the copper of the windings, forming harmful byproducts, such as Cu2 S. Different techniques to overcome the problem, including metal deactivation, oil change, and chemical treatment, have been applied. The long-term effectiveness of these techniques is examined and compared
Corrosive Sulfur in Insulating Oils: Its Detection and Correlated Power Apparatus Failures
No full textContamination of paper tapes by corrosive sulfur in insulating oils may cause shorting faults between turns. Typically, this occurs at higher temperature in the upper portions of the windings of shunt reactors and power transformers. In many of the tested oils, high amounts of dibenzyl–disul?de (DBDS) were found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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