Hydrogen gas generation due to moderately overheated transformer cores
This paper first presents an overview of this phenomenon from its initial discovery to the stage of the factory/laboratory investigations performed to confirm this new mechanism of gas generat ion in power transformers. This is followed by an overview of the increased significance of developing accurate calculation of the core hot spot temperature. The paper then presents the detailed accurate diagnosis performed on a 600 MVA transformer that had this issue in the field, the improvement made, and the calculation of the predicted gas generation performance of its loading cycle throughout a year of operation. The paper then presents the basis for the additions/changes proposed to be implemented in the IEEE Standards as a result of the discovery of this new gas generation mechanism. The paper also provides the basis for recommending to the IEEE Standards the selection of 130°C as the allowed maximum core hot spot temperature under sustained worst conditions of load, core — excitation and ambient temperature.
A study of the phenomenon of single excessive hydrogen in current transformers based on chemical theory
The phenomenon of single excessive hydrogen (SEH) is becoming increasingly common in domestic current transformers (CT) in resent years. This phenomenon has led to lots of maintenance work. However, no fault was found in those cases. And the cause of this anomaly has not been clarified. Thus, the aim of this paper is to find out the exact reasons underlying this phenomenon. In our study, potential sources of hydrogen production were analyzed based on the chemical composition and the properties of materials in CT. And possible causes were further calculated and analyzed according to the theory of chemical thermodynamics, dynamics, crystallology and catalysis principles. Then some simulation experiments were also performed to validate theoretical studies. It was confirmed that corrosion reaction of moisture in the insulating materials with active metals such as aluminum, zinc or iron is the only cause of SEH. Based on the cause, a linear model was established to describe the growth trend of the dissolved-hydrogen concentration in SEH. This study demonstrates that SEH has little correlation with latent faults. The lower limit of dissolved-hydrogen concentration in industry standards should be revised to reduce unnecessary maintenance work caused by this phenomenon.
Monte carlo simulation of events with Drell-Yan lepton pairs from antiproton-proton collisions
The complete knowledge of the nucleon spin structure at leading twist requires also addressing the transverse spin distribution of quarks, or transversity, which is yet unexplored because of its chiral-odd nature. Transversity can be best extracted from single-spin asymmetries in fully polarized Drell-Yan processes with antiprotons, where valence contributions are involved anyway. Alternatively, in single-polarized Drell-Yan the transversity happens convoluted with another chiral-odd function, which is likely to be responsible for the well known (and yet unexplained) violation of the Lam-Tung sum rule in the corresponding unpolarized cross section. We present Monte Carlo simulations for the unpolarized and single-polarized Drell-Yan pp{sup ({up_arrow}}{sup )}{yields}{mu}{sup +}{mu}{sup -}X at different center-of-mass energies in both configurations where the antiproton beam hits a fixed proton target or it collides on another proton beam. The goal is to estimate the minimum number of events needed to extract the above chiral-odd distributions from future measurements at the high energy storage ring (HESR) at GSI. It is important to study the feasibility of such experiments at HESR in order to demonstrate that interesting spin physics can be explored already using unpolarized antiprotons.