| Summary: | 博士 === 國立高雄應用科技大學 === 電機工程系 === 100 === The voltage ratings of the transmission line network of the Taiwan Power Company are categorized into 345kV, 161kV and 69kV. And overhead transmission lines, about 16,898 circuit-Km in length, account for 80% of the total length of the transmission lines, in addition to underground cables of 3,485 circuit-Km in length. It implies that most of Taipower’s transmission lines are exposed to atmosphere environments, and, thus, lightning is a potential major natural factor that might cause damages to the overhead transmission lines. Once a transmission line is struck by lightning, in serious cases, equipment and transmission line damages occur and an extensive area blackout is caused, even a system crash. In less serious cases, line tripping or instantaneous power failures are found. This is a serious economic problem to high-tech industries in Taiwan, and a source of public complaints in daily life. Taipower has been making efforts in this regard and adopts a lightning protection policy to reduce the adversary effects caused by lightning while the effectiveness is to be verified.
In this thesis, a software tool, the Alternative Transient Program - Electromagnetic Transient Program (ATP - EMTP) is used for simulation and analysis. It is employed to analyze the transient surge characteristics of transmission, to simulate metal oxide surge arrester models with fast surge impulse, following with a dynamic behavior, to simulate characteristics of arrester grounding lead at the platform steel frames, and to simulate different parameter effects on transient surge, etc. After the efforts, several transient protection methods are further used to clarify its specific effectiveness in the protection of transmission lines from lightning. These methods include: improvement of tower-footing resistance, installation of coupling ground wires, and installation of Externally Gapped Line Surge Arresters (EGLA).
During the period of this study, Taipower’s arresters installed at energized lines happened to have suffered lightning and caused overhead transmission line outages at the arc horn of post insulators of Air-Breaker Switch (ABS) and even caused a burning accident of Gas Circuit Breaker (GCB) at Taipower’s system. These once again caused voltage sag incidents and big economic loss.
To sum up, this study has proved to be very positive in the protection of transmission lines from lightning, in addition to prevention of the overhead and underground hybrid transmission system from transient over-voltage damages, and successful development of an oil-pressure on-line monitoring system. According to the analysis of lightning transient surge characteristics of the transmission line and the study of lightning protection policy in this paper, some positive results are reached. The results include: best allocation of arrester grounding leads and coupling wires, the installation of ABS at the open-ended point by the energized transmission line side on the effect of lightning protection, the influences of different system parameters on lightning transient surges, and successful development of an oil-pressure on-line monitoring system. These findings are accepted by Taipower, and in the process of extensive installation. This fact also shows that this paper will upgrade and benefit to the power supply quality and reliability of this state-run company’s transmission lines.
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