Power Grid Fault Diagnosis Oriented For Process Analysis

Power grid fault diagnosis system is used for quickly locating fault equipment, analyzing the action of protection and breaker after faults. It has great significance for improving the efficiency of fault handling and ensuring the rationality of the processing, which is the key problem of power grid dispatching intelligent decisions. In the current smart grid, the great access of new energy and the interactive requirements with users ask power grid operation to response faster, put forward more urgent practical requirements for the intelligent grid fault treatment decisions as well. This dissertation will get down to research from the following several aspects, including the completeness and interpretability of restricting the online operation of diagnositic system, the effectiveness under the condition of error fault informaiton and the maintainability of fault diagnosis system. With the whole process analysis of fault as the core, the dissertation study the practical and online powewr grid fault diagnosis by means of fault recurrence, whose main content are as follow:1. According to the basic theory of discrete event systems, the basic analysis model of power grid fault diagnosiso that oriented for fault process analysis is built, and the information gotten from the grid observation system is denoted by the set of observed events. Using the set of unobserved events, denote the events of fault equipment, the maloperation of protection and circuit breaker during faults. Combining observed events with unobserved events, the different fault hypothesis is built, and the generated method of unobserved events is created. The effective combination of power grid fault informaiton with diagnosis purpose by the model completely represent the fault process, and inhance the reliable explaning to fault diagnosis results for power grid.2. At the core of protective device, this dissertation researches the basic model of grid fault and build event constraints for discrete event in power grid. Network structure variation mode was established by analysing the logic of breaker tripped when the fault happens, which is used to implement the simple fault diagnosis; the action logic for relay protection devices is represented by dynamic fault tree, based on it, the action mode of relay protection is built. The logic relation among protective device, fault equipment and circuit breaker during faults is expressed as sequential events collection. Aiming at the actual configuration condition of the project site protection devices, combined multiple protection mode superposition with the network topology superposition method of the protection devices mode in the blackout area, the expression of possible events is implemented. According to analysis mode of power grid fault process based on relay protection devices, the single fault event constraints of observed events and unobserved events is confirmed and power grid fault process is reconstructed preliminarily.3. For the complete fault process of power grid, the method based on process matching is researched, which is used to diagnose single fault or all kinds of complex faults, such as developmental fault, multiple fault or cascading fault, and construct whole process of complex fault in power grid can be d. By means of connection analysis, the basic mode of grid framework change during faults has been analyzed. Then a method based on time sequence event of protection-circuit breaker action is put forward. By means of constructing predicate logic, the fault type criterion is illustrated, and the fault diagnosis flow based on process matching is designed. Finally, the effectiveness of the proposed method is verified by the developmental fault case actually occurred in a certain regional power grid.4. The method of power grid fault diagnosis considering error information is studied to adapt to complex data environment of project site, and ensure that the diagnostic system is reliable to solve under severe environment, such as no obvious fault feature, data error or no credible information. Then the measurement function of multiple fault hypothesis is constructed, and the multiple hypothesis generation strategy based on optimization algorithm is designed. With the method of unobserved events insert, observed events deflection and deleting, the strategy revising information loss, time gaps and information distorting is constructed. The method of power gird fault dignosis based on genetic algorithm with variable length chromosome is put forwatd, which can adapt to the dynamic change requirement of event hypothesis length, and analyse the whole process of comples faults contained multiple protection maloperation under the condition of incredible fault data. Finally, the effectiveness of the proposed method is verified by the developmental fault case actually occurred in a certain regional power grid.5. The method of automatically generated model method for power grid fault diagnosis is researched, to improve the practical level of power grid fault diagnosis system. Given the hundreds of even thousands of information of remote communication information which the dispatching automation platform of power grid expresses, power grid fault diagnosis modeling is very complex and tedious. In order to solve this problem, according to the basic data of the dispatching automation system, using semantic analysis and character disassembly technology, the automatic extraction of basic logic variables in remote communication diagnosis model is realized. Combining connection analysis with attributive analysis of remote communication information, the automatic representation of diagnosis model is completed. This method can adapte to the basic data of dispatching automation platform, and construct the action model of relay protection during faults according to the operation mode of power grid, to provide basic data for power grid fault process analysis.6. According to the actual requirement of power grid, there are four aspects to design the practical online power grid fault diagnosis system, the completeness of the diagnosis, the interpretability in the process of diagnosis, the effectiveness of diagnosis under the situation that Remote communication information is incorrect, the Maintenance friendly of the diagnosis system. Taking the power grid whole fault process analysis as key requirement, completing the diagnosis of multiple protection maloperation with the use of process matching. It shows the process of diagnosis and criterion of protection and breaker’s action to dispatcher through analysis the mode of protection’s action and the fault type, thus to insure the interpretability of the diagnosis. In order to adapt to the existed error in fault information, under the situation of complexiable data environment, this system adopt the Variable length chromosome coding of genetic algorithm to ensure the optimal explaination of the diagnosis process and reappear it to make sure if the fault information is crediable. This system build its protection mode based on the automaticl semantics analysis of Remote communication information and the relevance sequence relationship. The test case and online operation indicate clearly that the system can diagnose the power grid fault cantains multiple protection maloperation. In a nutshell, it can build the diagnosis model automatically based on the Power grid dispatching automation platform, and then solve the diagnosis problem under the situation that there are errors in fault information.