| Summary: | 博士 === 國立臺灣科技大學 === 電機工程系 === 96 === Abstract
This dissertation is concerned with the analysis and improvement of transient response on potential transformers applied to 161kV gas insulated switchgear (GIS) systems with SF6 insulation. The slow discharging overcurrent through the inherent line capacitance of underground inter-substation power cables may result in large magnetic force shifting and damaging bus potential transformer (BPT) primary windings of local substation when opening circuit breaker of remote substation located several kilometers away. The simulation models are built according to field parameters and the discharging current simulation results agree closely with those of field tests in electric power laboratory. BPT primary winding relocation may cause strongly different effects. Calculations are given to determine whether BPT can survive over the mechanical force resulted from the magnetic field generated by the aforementioned three-phase peak transient currents or not. Based on the newly improved BPT and its line-capacitance withstanding test, recommendations of BPT specification with respect to the maximum allowable line capacitance are also given.
In addition, while operating disconnecting switch or circuit breaker in distributed substation, an inductance-capacitance loop is formed from grading capacitor of circuit breaker to metering out-fit potential transformers (MPT) paralleled with the capacitance of GIS. Improper design of gap-core inductance damper equipped on secondary winding of MPT may cause ferro-resonance effect, resulting in over-voltage and serious over-current on windings of MPT to overheat and damage insulation material. Three kinds of efficient strategies are proposed in this dissertation to improve ferro-resonance effect on MPT applied to 161kV GIS, the corresponding equivalent circuit models are established and simulations of ferro-resonance based on the field parameters are given.
Simulation and experimental results show that the presented suppressors can quickly inhibit ferro-resonance in field test from damaging MPT, and assure safe and reliable switching operations.
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