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.

Este artigo aborda a Mostra Brasileira de Foguetes (MOBFOG) como uma ferramenta para o ensino de ciências e, para tal abordagem, é feita uma breve revisão bibliográfica sobre o ensino de ciências assim como acerca da MOBFOG em tal âmbito. Além disso, para entender as potencialidades das práticas com foguetes, são analisadas as respostas de um formulário eletrônico aplicado a estudantes que participaram da competição.

In this work it is proposed a scientific line of reasoning called Lucernics which aims to describe natural phenomena in terms of properties of light. It also carries out an analysis about how gravity could be intermediated by virtual particles similar to photons, namely guardions. It also proposes that massive bodies are sinks of guardions. When a massive body absorbs guardions from vacuum fluctuations, dark guardions are emitted. A dark guardion is a virtual particle which carries momentum in a direction opposite to its displacement. The time-derivative of this momentum describes a possible attractive force between massive particles which emit them. This derived force was compared to Newtonian gravitational force and the caliber constant obtained was equal to Planck's mass. This same study was done for electrostatic force, obtaining Planck's charge as a caliber constant. Newton's gravitational constant and Einstein's field equation were decomposed, and it also proposes a Lucernic Field Equation. The phenomena that this equation could describe will be discussed in future works.