Study On Risk Assessment Of Main Transformer Of Hydropower Plant

Along with the development of Smart Grid and Smart Plant, intelligent management of power plant equipment and condition based maintence have become development and research focus. Transformer, the key asset of plant, whose health level has a great significance in terms of the safe and economic opration of plant and grid. In old power plants, some transformer have oprated for a long time, some even have over 20 years, which has a high failure probability, means a serious threat to the security of transformer and system. To ensure the safe and stable operation of the transformer, State evaluation and risk assessment on transformer is necessary. Building a risk assessment model on transformer considering the influence of various factors, is of great significance to scientific management of transformer in plant.Risk assessment on transformer including three elements: assets and asset losses failure probability.The paper is based on State Grid`s “The transmission and distribution risk assessment guidelines”, research result of risk assessment and actual condition of hydropower plant, studing the risk assessment of hydroelectric power station main transformer, propoing risk models and the general process of hydropower plant transformer.Aiming at information redundancy and difference in test method in selecting state at the state evaluation and calculation of failure, the paper based on fault mode and effects analysis(FMEA) of transformer, using levels analysis method, establishing State quantity optimization model, optimization has selected oil color spectrum data including hydrogen(H2), and methane(CH4), and ethane(C2H6), and vinyl(C2H4), and acetylene(C2H2) this five species gas, oil test including moisture content, acidity, dielectric loss, breakdown voltage, moreover, furfural content.To improve effective use of various types of transformer condition imformation, the paper use a hierarchical model to assess the current status of transformers, taking a variety of State response to transformers' health status into consideration, which lower complexity of evaluation model. The first stage model has computed ageing coefficient, analyzing the current and future ageing of transformers. The second stage models has conducted chromatogram test, oil test, furfural content test, which responsing status indicators of transformers. The third stage model to amend the former two stage assessing results, analyzing the amendment of appearance condition, failure condition, defects condition, body preventive testing, casing reliability, reliability of voltage regulating switch, switch fault history, transformer reliability into former two stage of evaluation results. The paper has analyzed the current and future health index, the current and future failure rate through case of a hydro transformer. Considering grid performance, physical security, repair cost, environmental impact, and other aspects, the paper analysis the asset losses of the transformer. Proposing ways for grading the various elements of asset losses of the transformer. Synthesizing the evaluation of transformer losses, the asset evaluation, the asset loss evaluation results, calculated risk values for transformer, defines the risk levels of the transformer.To quantify the assest loss of transformer failure, the paper conduct a assessment, combining with knowledge of bidding, analyzing the relationship between the bidding system and risk assessment, bidding and maintenance strategy. Analysis result offers transformer maintenance decision-making references, which has a high practical value and significance.