Cristian Hans Correa

Thermographic inspections using drones with thermographic cameras have enabled considerable advances in preventive maintenance. In this context, we propose a methodology for prioritizing flight performance to ensure that the equipment is used in the most efficient way, based on the implementation of thermographic technology in the preventive maintenance plans of electric power concessionaires. Based on information about transmission lines obtained from the literature and made available by transmission companies, criteria and alternatives are established, and a methodology for prioritization and application in transmission lines is established using the AHP multicriteria method. Technical, safety, systemic, social, and financial criteria are defined, each containing alternatives, to define their weight and importance. Finally, through analysis of the four established criteria and alternatives, with their respective weights, a tool is obtained that will assist transmission concessionaires in the adequate prioritization of thermographic inspections using RPAS.

Linhas de transmissão (LTs) são usadas para transmitir energia elétrica guiada de uma fonte geradora para uma carga consumidora. A colisão e a eletrocussão são os principais impactos das linhas de transmissão de energia sobre a vida silvestre amplamente discutidas na literatura. No entanto, existem lacunas sobre as interações das aves silvestres com as LTs. O objetivo foi conhecer as espécies de aves que estabelecem interações com as LTs. Foram estudadas três LTs no estado do Rio Grande do Sul, durante o período de junho de 2023 a março de 2024. As torres foram vistoriadas com auxílio de binóculos, observando: data, horário, coordenadas geográficas, número da torre e a presença ou ausência de dispositivo antipouso (DAP). Quanto às aves nas estruturas, identificou-se: espécie, número de indivíduos, posição na estrutura da torre, comportamento, presença ou não de ninho. O monitoramento das 940 torres permitiu realizar 1.246 visitas: 383 registros com aves e 863 registros sem a presença. Vinte espécies de aves apresentaram interações com as LTs. Um total de 193 ninhos foram registrados em 12,3% das torres (n = 116) com 57% dos registros (n= 110) no estrato superior, 9,3% (n= 18) no estrato médio da torre e 33,7% (n= 65) no estrato inferior. Este modelo de dispositivo utilizado não está sendo eficaz para evitar que as aves construam seus ninhos. Testar a eficácia dos dispositivos implementados e realizar avaliações de monitoramento a longo prazo dos impactos produzidos por estas estruturas ajudará a encontrar estratégias para minimizar suas interferências.

In this work, a new methodology is proposed for the online and non-invasive extraction of partial discharge (PD) pulses from raw measurement data obtained using a simplified setup. This method enables the creation of sub-windows with optimized size, each containing a single candidate PD pulse. The proposed approach integrates mathematical morphological filtering (MMF) with kurtosis, a first-order Savitzky-Golay smoothing filter, the Otsu method for thresholding, and a specific technique to associate each sub-window with the phase angle of the applied voltage waveform, enabling the construction of phase-resolved PD (PRPD) patterns. The methodology was validated against a commercial PD detection device adhering to the IEC (International Electrotechnical Commission) standard. Experimental results demonstrated that the proposed method, utilizing an off-the-shelf 8-bit resolution data acquisition system and a low-cost high-frequency current transformer (HFCT) sensor, effectively diagnoses and characterizes PD activity in high-voltage equipment, such as surge arresters and instrument transformers, even in noisy environments. It was able to characterize PD activity using only a few cycles of the applied voltage waveform and identify low amplitude PD pulses with low signal-to-noise ratio signals. Other contribution of this work is the diagnosis and fault signature obtained from a real surge arrester (SA) with a nominal voltage of 192 kV, corroborated by destructive disassembly and internal inspection of the tested equipment. This work provides a cost-effective and accurate tool for real-time PD monitoring, which can be embedded in hardware for continuous evaluation of electrical equipment integrity.

Electromagnetic forces can lead to the structural failure of power transformers due to extreme loading conditions, vibration, and/or fatigue. Therefore, studying the nature and the magnitude of these forces is a key task in the design and failure analysis of such important equipment. Keeping this issue in mind, this work aims at conducting a numerical analysis in order to evaluate the mechanical stresses and displacements of windings in power transformers due to the action of electromagnetic forces. With this purpose, a finite element model is developed considering electromagnetic and mechanical effects assuming short-circuit conditions. The study compares the cases employing copper and aluminum windings with header tap, in different temperatures. The model developed in this work is verified against analytical solutions. The numerical calculations allow for performing a detailed analysis in terms of the distribution of both displacements and stresses along the windings, which is of great relevance for identifying critical structural points and avoiding structural failure. Overall, the obtained results demonstrate that the finite element model is a useful tool for the structural design of power transformers that allow for investigating and optimizing key aspects before manufacturing.

Acoustic inspection of distribution networks is seen as one of the main tools for identifying problems in electrical equipment at an early stage. As is often the case with predictive methods, the analysis of detected phenomena can reveal valuable information about the integrity of the equipment. Therefore, this article aims to evaluate the phenomena detected in a distribution network, with a primary focus on the occurrence of partial discharges identified through ultrasonic inspection. A digital ultrasonic testing device was used to detect acoustic signals emitted from an overhead distribution system, thereby gaining more experience in electrical equipment inspection and in the identification of partial discharges.

Electrical power systems are exposed to transient disturbances that change the voltage and current signals of the network, which can interrupt power and damage equipment. In high-frequency phenomena, it is essential to study the transient recovery voltage (TRV) to ensure the electrical insulation limits of circuit breakers are not violated, thus leading to a safe and reliable operation. Adequate models are crucial to achieving satisfactory results in the studies, according to the range of frequency of the transient being evaluated. This paper presents a comprehensive literature review of methods and models for studying electromagnetic transients, focusing on TRV requests imposed on circuit breakers, in addition to fault-clearing simulations on real system modeling. The analyses are fundamental both for the evaluation of the amplitude of the voltage signal and for its rate of rise. We also compare the reviewed models and techniques to provide a handy resource for researchers.

Acoustic inspection is a valuable technique that can detect early stage defects in equipment, thereby facilitating predictive maintenance. In recent times, ultrasonic sensors have made detecting partial discharges through acoustic sensing increasingly feasible. However, interpreting the acoustic signals can pose challenges, as it requires extensive expertise and knowledge of equipment configuration. To address this issue, a technique based on zero-crossing rate and fundamental frequency estimation has been proposed to standardize insulator diagnosis. In an experiment involving a database of 72 raw acoustic signals with frequencies ranging from 0 to 128 kHz, various types of pollution and defects were introduced to a chain of insulators. By employing the proposed technique, the occurrence of partial discharges can be detected and classified according to type, such as corona or surface discharges. This advanced approach to diagnosis simplifies the process while providing valuable insights into the severity of observed phenomena in the field.