Failure Rate Model And Overload Capability Of Oil-immersed Transformers

Oil-immersed transformers are widely used in electric power system. On one hand, oil-immersed transformers’stable and reliable operation is the premise of power grid’s safe operation. In order to increase the reliability indices of power grid further, it is an effective method to establish a device failure rate model based on the status detecting information. On the other hand, transformer’s overload running is required in some scenarios, such as regional load growth, failure accident, emergency load and outage maintenance. As a result, much attention has been focus on the research of exploring the hidden overload capability under the constraints of safety, reliability and economy. Then, the research results can be applied to make alternative dispatch strategies. The summary of main contributions in this dissertation is as follows.Firstly, a new oil-immersed transformer failure model, Arrhenius-Weibull-HI Model is proposed to reflect both permanent (aging) and repairable damages in terms of aging development and condition assessment. In this new model, Health Index was introduced to Aging Failure Model by building the relationship between Health Index and device life. It is proved that the new model can be described the historical failure rate data properly.Secondly, as the majority overload running scenarios are summarized, the overload capability of oil-immersed transformers is discussed under the constraints of winding hot spot temperature, failure rate and economic profit. Through these constraints, a new rule is proposed to make overload dispatch strategy. Then making the overload scenario of outage maintenance for example, a dispatch suggestion with the combination of load factor and period time is presented appropriately.Finally, the analysis results of overload capability, failure rate in overload period and overload strategy can be offered to power dispatch staff. Based on the rich information, and combining the concept of risk management and modern power dispatch method, the dispatch strategy can be optimized through a multi-target problem of low risk and high profit. According to this idea, the team, which author stayed, developed the "Smart Grid Risk Dispatch Strategy System Based on Equipment Overload Capability Analysis". In the system, one of the important modules called "Equipment Overload Capability Analysis" is introduced here. The main effects to achieve the module include the designs of development environment, database table and user interface.