Abstract
High-voltage direct-current (HVDC) transmission systems are considered an outstanding solution due to high electrical losses emerging from long-distance transmission. However, HVDC transmission lines (TLs) are vulnerable to lightning strikes. In this work, the Yunnan-Guizhou 500 kV HVDC transmission system is used as a case study to evaluate the impact of lightning strikes on DC-TL overvoltages, as no research studies have been conducted to assess the lightning transient behavior of DC-TLs. A comprehensive investigation of the 500 kV DC-TL transient performance during lightning strikes is performed, taking into account different technical aspects that have not been studied in detail by previous researchers. Additionally, analysis of the back-flashover phenomenon has not been conducted well in previous work, and results on the effect of changing the lightning strike current peak and tower grounding resistance on shielding-failure flashover are quite limited. The distributed-parameter model is used to represent the DC-TL using the electromagnetic transients program (EMTP), considering real parameters of shielding wires and DC towers to study the lightning impact in the case of back-flashover and shielding-failure phenomena. Lightning strike is applied to the shielding wire, and the impact of increasing the peak value of lightning current is investigated on the back-flashover occurrence. Moreover, the influence of tower grounding resistance variation on the transient overvoltages across the tower body and back-flashover phenomenon is evaluated. From the simulation results, increasing the lightning current peak and grounding resistance results in higher overvoltages across the tower body, which increases the probability of back-flashover. Additionally, the shielding failure of the TL is assumed, and the variation impact of the lightning current peak and grounding resistance on shielding-failure flashover is investigated. The results show that the impact of the lightning current peak has a more significant impact than the grounding resistance in the case of shielding-failure flashover.
Highlights
Power companies have started to pay more attention to the construction of highvoltage direct-current (HVDC) transmission systems, especially after the development of high-power electronic devices and control technologies [1,2]
The Yunnan-Guizhou 500 kV HVDC transmission system is used as a case study to evaluate the impact of lightning strikes, as no research investigations have been conducted to evaluate the transient behavior of DC-transmission lines (TLs)
This confirms that the proper design of the grounding system under the tower, which ensures smaller grounding resistance is essential for the protection of HVDC transmission systems from lightning strike hazards
Summary
Power companies have started to pay more attention to the construction of highvoltage direct-current (HVDC) transmission systems, especially after the development of high-power electronic devices and control technologies [1,2]. Transportation of a large amount of power over long distances (≥500 km) results in problems such as reduction of power transfer, generation of reactive power and voltage profile variation [3]. HVDC transmission is considered an optimal solution for connecting large-scale offshore renewable energy sources such as wind farms to power grids and linking distant generation sources with load centers [4,5]. In 1954, the first HVDC transmission project was constructed in Sweden [8]
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