This paper presents the application of grounding resistance measurement by fall of potential with high current injection, applied to the Transmission Line (TL) of 500 kV of Santo Antonio Hydroelectric Power Station (HPS), located in the city of Porto Velho/RO, for the commissioning of the power house grounding system in Generation Group (GG2) and TL during construction of the referred project. Based on measurements obtained in field, computer simulations were performed to assess the effectiveness of the grounding system on future fault scenarios of the TL, as well as the suitability of relevant protection functions. The computer simulations are based on the model developed for TL 500 kV of GG2, and are performed using the PSCAD/EMTDC software, including the grounding values derived from the design of high current injection, according to (IEEE Std 80-2013). In order to attest the efficacy of both GG2 grounding system and TL from the HPS, COMTRADE files, obtained by the software, were used in the simulator Doble 6150 for the design of distinct fault conditions in a SEL-421 relay. Results indicate the correct functioning of relay SEL-421, corroborating the effectiveness of both grounding system and measurement method.
Detection of high impedance faults (HIFs) in distribution systems is a challenging task, which has attracted the interest of the researchers for decades. The HIF current random behavior and its lowmagnitude cause difficulties for a reliable detection by traditional protection methods. Therefore, the hazards for grid devices, people and animals safety, associated with HIFs, motivate the research of new detection techniques. However, there is no fully efficient solution for this problem. In this context, this paper aimed to characterize HIFs by a set of real measurements considering different type of soils employing Fourier (FT), Wavelet (WT) and Stockwell Transforms (ST). The measurements were performed at the fault spot in a medium voltage test field specially built for this purpose. The idea is to highlight key characteristics of the HIF current waveforms pointed out by each of transform and assess which ones can be used as a promising tool for HIF detection. The results showed that the HIF current can be characterized by the interharmonic behavior during the fault, extracted by FT and by the high degree of energy variations at specific decomposition levels of WT and ST.
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