Health Diagnosis And Hidden Fault Identification For Complex Distribution Grid

With the rapid growth in electricity loads and the improvement of power supply reliability, the scale of the distribution grid represented by cities and load concentrated regions is getting bigger and bigger, and its topology is more and more complex. Its operational complexity is greatly increased because of the access of distributed energy and the application of the electric car charging station at the same time. Such, the traditional fault diagnosis technology aimed at occurred fault of distribution network cannot meet the demand of safe, reliable and economic operation. Therefore, it is quite necessary to discuss the real-time health diagnosis of complex distribution grid (CDG).Regarding CDG as a living body, introduce in the concept of CDG health diagnosis and use health index system to describe its functionality and performance conditions by means of the analogy of CDG health status and human health state.Screen index by considering primary-secondary effect as well as internal and external influence factors. Determine the health standard of each index and establish a quantitative reference frame to measure its health state. Find its gap and changing trend by compared with the reference frame, and then give response action suggestions to the abnormality occurred or likely to occur to guarantee that it is in a stable health state. Verify the applicability and accuracy of the diagnostic structure by analyzing certain real lOkV distribution network including health assessment of the system in small time scales and health trend prediction in large time scales.The study of hidden failure is a new focus of power system fault diagnosis in recent years. The hidden failure of CT/PT has a direct impact on the normal work of equipments such as relay protection etc. Few studies have been done on the research of transformer hidden failure in contrast with the study of relay protection and breaker etc. The main manifestations of transformer hidden failure is analyzed and summarized in this paper. Establish the relationship between every branch power and its current using power flow tracing technology and Analytical Redundancy Relation (ARR), and recognition its hidden failure by verifying whether the residual vector satisfy the constraint condition or not. The analysis result of a5nodes distribution network shows that this method is capable to recognize the hidden failure and other abnormality. This paper finally gives a method of CDG health diagnosis which is helpful for dispatchers to master the health state and operation trend of the system, and achieve the expansion of the previous fault diagnosis in content, time and space. Meanwhile, study on the recognition of the hidden failure of CT/PT, which could be a supplementary to the research.