A Study of Lightning and Ground Fault Characteristics for VHV Transmission System with Overhead Lines and Underground Cables

• Main Authors: Feng-Kai Tsao, 曹峰愷
• Other Authors: Chih-Ju Chou
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/rr6u9y

碩士 === 國立臺北科技大學 === 電機工程系研究所 === 102 === It is more and more popular that very high voltage (VHV) transmission system is composed of overhead lines and underground cables. Such system needs cable connection station (CCS) for overhead lines and underground cables connections. The system frameworks and line parameters are discontinue at CCS, which let the electrical faults to happen easily; where the faults associated with lightning and ground fault are the most of all. The faults usually caused to the damages on the equipments of CCS and underground cables, and thus cause to serious affection on power transmissions. These faults are in urgent need of study and solutions. This thesis will aim to study these faults for typical 161kV transmission system with overhead lines and underground cables, in which, the lightning and ground fault characteristics are analyzed, and the damages due to the faults are evaluated. Also, the mitigated strategies are proposed. First of all, system modeling and analysis are based on the alternative program (ATP) of electromagnetic transient program (EMTP). The system model will cover the transmission lines and their upstream and down stream substations. The upstream substation is extra-high voltage substation (E/S) where the 345kV/161kV main transformer and the equivalent 345kV system source are considered in the model. Meanwhile, the down stream substation is modeled as an equivalent load connected with a 161kV other line system source. As to transmission line, the typical 161kV double-circuit transmission lines are considered, in which the detail ATP models of overhead lines, underground cables and CCS should be constructed with respect to analysis items, i.e., the detail ATP models are constructed for different lightning and ground fault locations. Then, the voltage and current variation of various important points are analyzed based on ATP simulation by these models. The insulator voltages, tower section potentials and foot ground potential rises, CCS arrester voltages and currents, the voltage and current distribution on cable shields and auxiliary grounding wires, and voltages and currents on the surge suppressors in the cable cover protection units (CCPUs) can be obtained from the ATP simulation results. In addition, the simulations will consider the situations of overhead lines with and without line arresters, and the underground cables with different frameworks. Finally, based on simulation results, the damages due to lightning and ground fault are evaluated. The damages on overhead line insulators, CCS arresters, cable joints and CCPUs will be further surveyed, and the mitigated strategies are proposed.