An Improved Statistical Method for Calculating Lightning Overvoltages in HVDC Overhead Line/Cable Systems

Lennerhag, Oscar; Lundquist, Jan; Engelbrecht, Christiaan; Karmokar, T.; Bollen, M.H.J.

doi:10.3390/en12163121

Cited by 8 publications

(3 citation statements)

References 8 publications

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“…Many researchers have studied the impact of lightning strikes on mixed transmission lines since the 1990s and several resulting articles have attempted to address various aspects of lightning transients in mixed HVDC as well as HVAC lines [6][7][8][9][10][11][12][13][14][15][16]. Many of these studies focused on specific design aspects such as the shunt reactor on cable terminal, presence of surge arrester/sheath voltage limiter, OHL geometries and tower footing impedance.…”

Section: Introductionmentioning

confidence: 99%

Assessment of Overvoltage and Insulation Coordination in Mixed HVDC Transmission Lines Exposed to Lightning Strikes

et al. 2019

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Many geographical constraints and aesthetic concerns necessitate the partial use of cable sections in the High Voltage DC (HVDC) transmission line, resulting in a mixed transmission line. The overhead sections of mixed lines are exposed to lightning strikes. The lightning strikes can not only result in flashover of overhead line (OHL) insulators but can enter the cable and permanently damage its insulation if adequate insulation coordination measures are not taken. In this work, we have analyzed the factors that affect the level of overvoltage inside the cable by simulating a fast front model in PSCAD. It has been determined that surge arresters must be provided at cable terminals when the length of cable sections is less than 16 km to limit the core-ground overvoltage within the lightning impulse protective level (LIPL). The level of sheath-ground overvoltage is independent of the length of cable; however, it can be limited within LIPL by lowering the sheath grounding impedance to 1.2 Ω. Insulation coordination measures do not impact the likelihood of OHL insulators’ flashover. The flashover performance of OHL can be improved by lowering the footing impedance of the second tower closest to the cable terminals, which is otherwise most likely to flashover.

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Section: Introductionmentioning

confidence: 99%

Assessment of Overvoltage and Insulation Coordination in Mixed HVDC Transmission Lines Exposed to Lightning Strikes

et al. 2019

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“…Basically, the backflashover risk depends on factors such as the density of ground flash (Ns, flashes/km 2 /year), the peak value of lightning current and the tower footing resistance. For the back-flashover phenomenon, the annual number of lightning strikes (N b ) to a 100 km transmission line is estimated as follows [50]:…”

Section: Simulation Resultsmentioning

confidence: 99%

Evaluation of the Transient Overvoltages of HVDC Transmission Lines Caused by Lightning Strikes

et al. 2022

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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.

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“…Most commonly, the mixed overhead cable lines are applied. This, however, causes the cable exposition to overvoltages evoked by direct lightning strikes to overhead power lines [1][2][3][4][5][6]. Figure 1 has shown the cross-section of high power single-conductor cables with indicated overvoltages on insulation u in and on outer sheath u os .…”

Section: Introductionmentioning

confidence: 99%

Study of the Lightning Overvoltage Protection Effectiveness of High Voltage Mixed Overhead Cable Power Lines

et al. 2021

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In this paper, the effectiveness of lightning overvoltage protection of cables in high voltage overhead cable lines has been analyzed. Because of the high overvoltage level, the cables are protected by surge arresters and by metallic sheath earthing. However, in practice, quite a lot of cases of electricity-evoked damage to the cable outer sheaths are observed, proving that the effectiveness of the protection used is insufficient. As a result, the cables are exposed to environmental factors, especially moisture penetration, which contributes to cable degradation. To explain the causes of this situation, simulation studies were carried out to determine the relevant factors affecting the level of expected overvoltages. The circuit-field model of the overhead cable line in EMTP-ATP, COMSOL and MATLAB software was used for determining overvoltages on the main cable insulation and the outer protective sheath. The studies reveal that the efficiency of the cable insulation overvoltage protection is ensured regardless of the lightning strike location and the crest value of its current. However, the obtained results confirm that no matter the applied protection, the cable outer sheaths may be exposed to overvoltages with higher values than those of the main insulation. Although the analysis was performed for 110 kV lines, the conclusions are general and are also applicable to power lines with higher rated voltages.

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An Improved Statistical Method for Calculating Lightning Overvoltages in HVDC Overhead Line/Cable Systems

Cited by 8 publications

References 8 publications

Assessment of Overvoltage and Insulation Coordination in Mixed HVDC Transmission Lines Exposed to Lightning Strikes

Assessment of Overvoltage and Insulation Coordination in Mixed HVDC Transmission Lines Exposed to Lightning Strikes

Evaluation of the Transient Overvoltages of HVDC Transmission Lines Caused by Lightning Strikes

Study of the Lightning Overvoltage Protection Effectiveness of High Voltage Mixed Overhead Cable Power Lines

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