Bushing failure in power transformers and the influence of moisture with the spectroscopy test

Distribution and Power transformers and their accessories are the main and important equipment used in the power system, one of their most delicate component is the bushing, and the first failure mode is the moisture. The moisture in the bushing appears in oil-paper (Kraft) insulation, the influence is in the insulation, it acts as a catalyst, due to the insulation degradation and aging. In that way, is very important to detect accurately the presence of humidity and water content within the insulation (oil and Kraft) early as to evade any pre-mature catastrophes. The 2 basic bushing scheme are non-graded and capacitance-graded. The prior is the simplest and the oldest bushing. The capacitance graded bushings are obtainable in four technologies: (i) Epoxy Resign impregnated paper (ERIP), (ii) Resin Impregnated Paper (RIP), (iii) Resin Bounded paper (RB), (iv) Oil-Impregnated Paper (OIP). The last one is the most common bushing. The explosion is the last stage for a failure, it begins with the bushing degradation. The last stage is frequently an expensive and catastrophic failure for the power system, this bushing cannot be repaired. In nowadays, the maintenance routine required a condition check, however, the traditional methods, for capacitive bushing, are inspections, capacitance, PFs, for non-capacitive are watts dissipated and inspections. In this research a study with a possibility of frequency domain spectroscopy (FDS), as frequency domain techniques (FDT), the measurements is developed, for bushings in the inductive equipment, and the limit failure has been done. An important knowledge contribution to the moisture in the bushing has been developed and the needed to update the international standards IEC 60137, IEC 60296, IEC 60422, ASTM D 3487 and ASTM D1305, it is one of the main points in this paper. On the other hand, the electrical capacity such as FDS is ideal, because of its straightforwardness and pragmatism. The goal of the research is to study and investigates the claim of FDS method and its swaying features under site acceptance test (SAT), condition using OIP model with disparities as temperature, aging rate and the conductivity for oil and paper. Finally, the research proposes new limits for bushing in power transformers, likewise, the assessment of this assets with a new update in the internationals standards.