Abstract
HVDC systems are becoming more common worldwide, specially in Brazil, since the adoption of such system for Itaipu’s hydroelectric complex in the 1980’s. Today, the country has the Xingu-Estreito bipole, with length of 2375 km. This system crosses a region with high lightning incidence, a phenomenon which causes faults in power systems. The most widely used model for the positioning of the arrestor cables over a transmission line is the electrogeometric model. This model, however, does not take into account the different potentials over the structure’s surface, and therefore presents significant inaccuracies when assessing the risk of lightning strikes on structures such as a HVDC line. This work then used the Electric Field Deflection (EFD) model with the aid finite elements. Four levels of lightning are assessed (I, II, III and IV), with current peaks of 3.9, 5.4, 10.1 and 15.7 kA. It was verified that the positive pole tends to attract most of the lightning with shielding failures width (SFW) of 12, 8, 4 and 0 m. It was then proposed to move the arrestor cables horizontally. The study indicates that this horizontal shifting of the cables in 5 and 8 m toward the side with larger chance of direct incidence reduces the shielding failure widths in 50% for peak current of 3.9 kA and almost eliminates the strikes for lightning with peak currents of 5.4, 10.1 and 15.7 kA.
Highlights
The introduction of new energy sources to the classically thermal and hydroelectric power grid brings the necessity of more flexible alternatives to ensure the best performance of large-scale power transmission [1,2]
We proposed that the arrestor cables in High VoltageDirect Current (HVDC) transmission lines be no longer symmetrically positioned (Figure 5b)
The analysis by Electric Field Deflection (EFD) indicate that the positive pole of the HVDC line is more vulnerable to direct strikes than the negative one, given that cloud-earth lightning with negative charges are the most frequent in nature
Summary
The introduction of new energy sources to the classically thermal and hydroelectric power grid brings the necessity of more flexible alternatives to ensure the best performance of large-scale power transmission [1,2] In large systems, such as the ones that extend over countries with large territories, like those of Brazil, India, China and the USA, this need is being met through the use of High Voltage. It is common knowledge that a strong commercial dispute over the hegemony of the generation, transmission and distribution of electricity to the general population took place This dispute, referred to as “war of the currents” in history and popular culture, reached its peak during the 1880’s and 1890’s and was championed on one side by Thomas Edison, proponent of direct current systems and, on the other side, by George Westinghouse, advocate of alternate current systems [3]. The predominance of alternate current systems can be attributed mainly to the advent of electric transformers, developed commercially by William Stanley, which enable an easy conversion of Energies 2019, 12, 555; doi:10.3390/en12030555 www.mdpi.com/journal/energies
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