Research On Comprehensive Evaluation For Security State Of Traction Substation Grounding Grid

The gradual maturity of electrified railways has put forward higher requirements for the security and reliability of traction substations, while traction substation grounding grid is an essential link to maintain the safe and reliable operations of traction substations and protect personal safety. So a reasonable assessment of the security of grounding grid can avoid the occurrence of a number of accidents and protect the safe and stable operations of the traction substation system.The dissertation begins with elaborating the fundamental knowledge regarding traction substation grounding grid, including introduction to the composition and safety of grounding grid and focusing on the technical indexes and measureme nt methods of important parameters concerning grounding grid, such as ground resistance, contact voltage, step voltage, electrical integrity and soil resistivity.Secondly, a comprehensive evaluation is made of the security condition of traction substation grounding grid. Since the current security evaluation has merely taken into account whether each characteristic parameter has met their specified limits, the safety grading assessment is solely based on engineering experience, which makes it far from accurately reflecting the security status. To address the above problems, the dissertation fully considers characteristic parameters while establishing a comprehensive assessment model regarding grounding grid security based on the dynamic trend(DT) method and rough set theory. Moreover, its feasibility is verified by using engineering examples.Finally, hazardous areas of traction substation grounding grid assessed further accurately locate the fault location of grounding grid corrosion. By using the node tearing approach, a ground grid is partitioned and a multi-objective optimization function is established to reduce the constraints, and then an improved immune genetic algorithm is employed to solve the diagnostic model and good diagnosis results have been gained.The application and analysis outcomes of a traction substation grounding grid project have shown that the dissertation makes a comprehensive security state assessment for the traction substation grounding grid by employing the DT method and rough set theory, and identifies the specific fault location of grounding grid corrosion by using the improved immune genetic algorithm, which have yielded the same analytical results with the actua l situation. These methods are simple and effective. In this way, a good theoretical foundation has been laid for practical applications in engineering.