| Summary: | 碩士 === 國立臺灣科技大學 === 電機工程系 === 106 === With the rapid development of science, technology and economic activities, the society has paid more and more attention to the power quality and supply security. Electric power companies increasingly adopt the gas insulated switchgear (GIS). It uses SF6 as insulated materials and contains bus, circuit breakers, disconnect switches, earth switches, current transformers and potential transformers. The design of GIS not only greatly reduces the construction space, but also improves the convenience of maintenance and the safety of operators.
In order to effectively cut off the transient overvoltage caused by switching on, one solution is to connect a circuit breaker to a grading capacitance. However, while the circuit breaker opens, there will be a loop between the grading capacitance and the load. If and only if the core of the potential transformer is saturated, it is easy to happen ferroresonance, which causes the abnormally continuous overvoltage and overcurrent between the grading capacitance and the potential transformer. In some serious case, ferroresonance leads to insulation deterioration, short circuit, equipment damage or even blackout.
Therefore, this thesis aims to propose a freeoresonance analysis strategy. With the EMTP-RV software, the overvoltage and overcurrent of ferroresonance will be simulated. Different suppression methods will also be evaluated. For related engineering personnel, the strategy can provide a faster way to rebuild the process of ferroresonance faults, accelerate the search of solutions and enhance the reliability of power supply.
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