Study Of Transformer Operating Performance Based On SCADA Measurements

With the wide use of SCADA measurements and the development of monitoring technology of equipment, it makes more possible to grasp the overall performance of transformer. Besides, the performance of the power grid equipment aging is a gradual process of quantitative change. It is more important to find the gradual deterioration trend of the overall performance of the transformer with tapping into measurement information. In this way, the aid for transformer maintenance, the longer service life and high efficiency along with the minimal loss will realize. Transformer is the main part of a substation. The auxiliary health assessment of the transformer can generalize to the health of the whole substation through measurement information, and contribute to the substation’s safe and reliability.First, in this paper, the operating performance of the transformer is expressed by characterizing SCADA measurement information. The structural performance is the internal reflection of the overall performance of transformer, besides, the operating performance is the external reflection of the overall performance of transformer. By using the generalized volt-amperes characteristics, the interactional relationship between the structural performance and the operating performance is analyzed. Using electric parameters information can explicitly express the transformer structural performance in a feasible way. The performance indexes can evaluate the operating performance of the transformer, and then reflect the structural performance of transformer which reflects the transformer health.Second, using T equivalent circuit of transformer instead of the basic structure and also using SCADA measurement information, the structural performance is associated with the operating performance through the generalized volt-amperes characteristics along with the establishment of the equivalent physical model of transformer.4 quantitative indexes of structural performance of transformer are unearthed based on SCADA system measurement information:the winding resistance index, the leakage reactance index, the impedance module index and the efficiency index. Demonstrate that the structural performance is effected by the model error of the corresponding index, which is ready for further analysis of the measurement error. The corresponding dialectical relation between each of the performance indexes and the changes of external conditions for the influence of the relationship between the various indexes are discussed.Taking the winding resistance index for example, the relationship between the performance indexes and the measurement error is discussed, demonstrating that when the electric parameters measurement error meets normal distribution, the error of performance indexes satisfies normal distribution and the bad data of the electric parameters can be directly reflected in the indexes’ normal distribution. The measurement information is regarded as random process, with the data of each day as a sample information. The statistical rules of performance indexes are excavated and the definition of the mean sequence of the daily cycle sequence is provided. Based on the normal distribution of random process theory and the dialectical relationship of each index, the assessment of the structural performance of two winding transformer and three winding transformer is established. Defining the observability of substation, the evaluation about the structural performance of transformer is generalized to the evaluation about the structural performance of substation.Finally, according to the proposed performance indexes of two and three winding transformer based on the theory of normal distribution, examples are provided. By using PSCAD simulation, the first part of the examples illustrates that the changes of the internal structural performance of transformer and the changes of the current coefficient have influences upon the winding resistance index and the leakage reactance index. The second part of the examples is validated that three winding transformer performance indexes satisfies normal distribution according to the actual data. Based on the normal distribution of random process theory and the dialectical relationship between various indexes, the health of the three winding transformer is determined. The third part of the examples illustrates the health of a simple substation using two winding transformer model, which demonstrates the effectiveness and feasibility of this article.