| The self-designed1000-kV Ultra-high Voltage (UHV) AC electric power transmission pilot project from Changzhi in Shanxi Province to Jingmen in Hubei Province has the highest AC voltage level with the advanced technological content at present. To increase its power transmission capability, improve the dynamic performance and power system stability, research staff in State Grid Corporation of China (SGCC) developed the first set of1000-kV UHV series capacitor banks in the world, and now it has been put into operation.However, in switching operation of UHV series capacitor banks, not only be transient primary-system overvoltage and secondary-system disturbance introduced, but transient overvoltage and current be caused on nearby capacitor voltage divider as well. Under the background of establishing robust physical power network and promoting UHV-related power industry, a series of technical problems such as switching overvoltage and electromagnetic compatibility arise in designing and developing the first set of1000-kV UHV series capacitor banks. Aiming at solving these problems, the principal content and achievements of this dissertation is listed as following:First, a transient electromagnetic measurement system was developed and measurement method on high-potential platform of UHV series capacitor banks was proposed. A series of performance test including shielding effectiveness, voltage withstanding ability, electromagnetic immunity, etc. were carried out to verify the reliability and adaptability of the measurement system mounted on the high-potential platform of UHV series capacitor banks where the electromagnetic environment is very intense. Other functional characteristics of the transient electromagnetic measurement system featuring optical fibre communication, independent uninterrupted power supply, ungrounded measurement, remote monitor and control, low load impact, and so on.Second, by applying the transient electromagnetic measurement system and using the1000-kV life-size experimental platform of UHV series capacitor banks, disconnecting switch experiment was carried out. Thereby, transient characterization of on-platform primary-system overvoltage and secondary-system disturbance was achieved after statistical analysis of experimental data. Furthermore, on-platform grounding schemes of the secondary system were investigated, and better grounding schemes of the shielded cable and secondary sytem were determined. Some of the experimental results had been applied in overvoltage suppression and EMC design of the first set of1000-kV UHV series capacitor banks.Third, by utilizing the above-mentioned measurement system again, experiment was conducted in examining the impact of switching operation of1000-kV UHV series capacitor banks on nearby capacitor voltage divider. So transient characterization of voltage and current of1000-kV capacitor voltage divider was achieved, and corresponding endurable transient overvoltage and overcurrent level were given. At the same time, transients suppression schemes including inserting protective resistor and inductor in series with capacitor voltage divider were evaluated and verified in allievating transient overvotlage and current. The experimental results shed lights on compatible operation of series capacitor banks with its nearby capacitor voltage divider.Fourth, a circuit modeling method with partial inductance featuring weakly coupled T-type element equivalent circuit was proposed. On this basis, a computer code MSCM (Matrix Sparsification and Circuit Modeling) was formed, which is used for sparsifying circuit parameter matrix and generating SPICE-compatible circuit model. It realizes that to extract circuit paramter matrix for a large-scale multiconductor system and to develop corresponding circuit model are possible. The numeric experiment reveals that the method increases the circuit simulation efficiency of large-scale multiconductor system significantly when maintains the same simualtion accuracy with full circuit parameter matrix. Applying this circuit modeling method and MSCM, the wideband circuit model of UHV series capacitor banks was established and verified both on laboratory model and1000-kV life-size UHV series capacitor banks. Thereby, the transient electromagnetic process due to bypass gap sparkover and disconnecting switch operation was simulated, and the on-platform overvoltage suppression effectiveness by using a nonlinear resistor in parallel with a pulse capacitor of was evaluated.Fifth, the wideband impedance data of UHV capacitor voltage divider was measured in frequency domain using two different methods, and impedance simulation result was compared with measurement data to validate the impedance measurement data. In addition, a written computer code CMFI (Circuit Modeling for Frequency-dependent Impedance) was deployed to generate a wideband circuit model with physical denotation for the capacitor voltage divider. Furthmore, circuit network functions were defined to evaluate the performance of capcitor voltage divider and analyze its sensitivity around the designed value. Some proposals on improving the functionality of capacitor voltage divider were also derived, which helps improve the optimized design. Incorporated with the wideband circuit model of1000-kV UHV series capacitor banks, the transient process in capacitor voltage divider due to disconnecting switch operation was simulated, and the suppression method of transient grounding current of capacitor voltage divider was analyzed as well, which enlighten the compatible operation of series capacitor banks with nearby capacitor voltage divider in UHV substations. |
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