A Study of Ferroresonance Suppression for Potential Transformers with Circuit Breaker Grading Capacitances and Predictive Maintenance for ZnO Arresters

  • 謝 建賢

Student thesis: Doctoral Thesis


To ensure a safe operation in a complex power network utility engineers often regulate certain compensation equipment and install protection devices to increase the power system security However because of distinctive features of each power equipments there exists a possibility of risk hence damaging the power grid For example the operation of potential transformer is easy to generate a ferroresonance with capacitive elements or circuit breaker grading capacitance so as to result in overvoltage and overcurrent bringing in the overheat of transformer coils the saturation of iron cores and the insulation breakdown of equipment A real case of bus PT ferroresonance was observed in a gas-insulated substation Therefore the study on the generation of ferroresonce as well as a systematic way of suppressing such nuisances has become one of important topics in power system operations Next in order for restricting the overvoltage caused by the ferroresonance the ZnO arresters are often used against surge overvoltages Yet the increased leakage current due to the degradation of a metal oxide arrester would result in overheating largely shortening the operation life of arresters Moreover since the arresters are often formed by several sections of zinc oxides where the level of degradation at each section is different the detection of overall leakage current would be insufficient to identify the location of faulted section A method of justifying the faulted location of an arrester is being deemed as one of important topic in power engineering studies In view of aforementioned problems this dissertation is devoted to developing a method of ferroresonance detection and suppression by which the reason of ferrresonance occurrence can be evaluated and the suppression of this event is investigated as well In addition the leakage current and temperature measurement techniques are integrated with a new mathematical algorithm to increase the predictive maintenance capability of ZnO arresters These proposed methods are evaluated through software simulations and field validations The test results confirm the feasibility of the proposed methods for the detection and mitigation of ferroresonance as well as for the maintenance improvement of arresters benefitting the reduction of transmission risks and the increment of grid operation safety
Date of Award2015 Feb 5
Original languageEnglish
SupervisorShyh-Jier Huang (Supervisor)

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