Transformer health status evaluation model based on multi-feature factors

Abstract

During the entire period of transformer's service, the internal parts get ageing gradually. But the aging degree of each part cannot be observed directly. To correctly master the condition of the transformer contributes to the prediction of the risk and reliability of the transformer, and also, this is the foundation of making effective repairing strategies or replacement, ensuring the safe and reliable operation of transformers. However, the exact assessment result has not been acquired according to traditional assessments that based on only one of the state parameter. A new assessment model based on the multi-feature factors is proposed to overcome the disadvantage of traditional condition assessments. Firstly, in order to find out the rule that the characteristic of transformer changes, the factors that influence the state of the transformer health are researched with the method of the correlation analysis of Mathematical Statistics. These factors include DGA, breakdown voltage, dielectric loss, micro-water content, acid value, furfural content and so on. Secondly, determine the state information of the power transformer; establish the index system for health evaluation. Combining with qualitative analysis, the analytic hierarchy process method is adopted to determine the weight of each index, and the health status evaluation model of power transformer is established. As for a transformer that is in operation, as long as the corresponding experimental data is got, the health condition of the transformer can be obtained with the help of the health status evaluation model. Take transformers of a substation for instance. Using the proposed model, the corresponding experimental data is analyzed. The investigations results show that the new health status evaluation mode is effective.the aging process of the transformer, and the load of the transformer and the environment conditions are closely related. Factors that account for the transformer insulation aging include over-current, long time of high-load operation, overheating, moisture, oxidation, etc. Heat and moisture are the most important factors for liquid insulation aging, whereas oxidation can seriously accelerate the degradation of solid insulation. If the stage of insulation life can be de obtained effectively by means of the necessary monitoring and testing in the process of transformer operation, the service life of transformer can be maximized under the premise of reliability. This can not only guarantee the safe and stable operation of power system, but also reduce the operation costs. Evaluate the status of the transformer insulation correctly, predict the risk and reliability of its operation and then make effective economic management of maintenance and replacement strategy. This is the imperative trend of power industry development.: Associate Professor of Electrical Engineering, Wuhan University, Chioa. Research field is electrical equipment, agiog mechanism, fault diagnosis, condition assessment and maiotenance strategy. Mailbox: songbin72@163.com

Calculation of a Health Index of Oil-Paper Transformers Insulation with Binary Logistic Regression

“…The health index is 0.816 calculated with formula (5). According to Figure 4, the health condition of the transformer is very bad and nearly out of service, the same conclusion with higher calculation efficiency with [25]. Table 12: Comparison of the health conditions produced by the presented method and the health conditions produced by method in [26].…”

“…Another 110 kV transformer, shown in [25], has been in service for 25 years until April 2014 in China. No accident has ever happened with good running environment and load rate is about 0.8.…”

Condition Assessment of Power Transformers Based on Health Index Value

“…The general principle of creating a health index is that there is a necessity to consider the impact of individual test results on the transformer's technical condition and the development of aging processes. One of these proposals is presented in detail in [11]. The algorithm I contains four The transformers in the control group were chosen to minimize the impact of various variables regarding their construction and exploitation.…”

“…The general principle of creating a health index is that there is a necessity to consider the impact of individual test results on the transformer's technical condition and the development of aging processes. One of these proposals is presented in detail in [11]. The algorithm I contains four categories of parameters, which include the physicochemical properties of the oil (HI OIL ), the content of gases dissolved in the oil (HI DGA ), the condition of solid insulation of windings (HI ISO ), and the age and history of the unit's work (HI AGE ).…”

Electric Vehicle Charge Stations Location Analysis and Determination—Ankara (Turkey) Case Study

“…From [30], where C f ur is content of furfural to determine, HI f ur is the index of it, from [28] C f ur = 5 means that the transformer is deteriorated and it can break down, in this condition HI f ur = 6.5. On the other hand C f ur = 0.01 when it is newer and HI f ur = 0.5.…”