Probabilistic Methods For Counting Equipment Trips Due To Voltage Sags

Este artigo tem por objetivo analisar a interdependência entre a operação de conversores de freqüência tipo VSI-PWM e uma das manifestações mais comuns para a perda de qualidade de um suprimento elétrico, qual seja, a ocorrência do fenômeno denominado por afundamento temporário de tensão ou "voltage sag". São apresentados resultados de simulações, realizadas no Simulador Saber, de um sistema típico submetido a afundamentos de tensões simétricos e assimétricos. Resultados de ensaios em laboratório também são fornecidos com vistas à validação dos resultados computacionais. Aspectos relacionados com a capacidade "ride-through" dos conversores e correspondentes arranjos de proteção são também considerados.

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A Method for Extracting Some Key Terrain Features from Shaded Relief of Digital Terrain Models

Remote Sensing ◽

10.3390/rs12172809 ◽

2020 ◽

Vol 12 (17) ◽

pp. 2809

Author(s):

Meirman Syzdykbayev ◽

Bobak Karimi ◽

Hassan A. Karimi

Keyword(s):

Land Surface ◽

Basic Research ◽

Probabilistic Methods ◽

Detection Methods ◽

Computational Techniques ◽

Surface Evolution ◽

Dem Analysis ◽

High Degree ◽

Terrain Features ◽

Shaded Relief

Detection of terrain features (ridges, spurs, cliffs, and peaks) is a basic research topic in digital elevation model (DEM) analysis and is essential for learning about factors that influence terrain surfaces, such as geologic structures and geomorphologic processes. Detection of terrain features based on general geomorphometry is challenging and has a high degree of uncertainty, mostly due to a variety of controlling factors on surface evolution in different regions. Currently, there are different computational techniques for obtaining detailed information about terrain features using DEM analysis. One of the most common techniques is numerically identifying or classifying terrain elements where regional topologies of the land surface are constructed by using DEMs or by combining derivatives of DEM. The main drawbacks of these techniques are that they cannot differentiate between ridges, spurs, and cliffs, or result in a high degree of false positives when detecting spur lines. In this paper, we propose a new method for automatically detecting terrain features such as ridges, spurs, cliffs, and peaks, using shaded relief by controlling altitude and azimuth of illumination sources on both smooth and rough surfaces. In our proposed method, we use edge detection filters based on azimuth angle on shaded relief to identify specific terrain features. Results show that the proposed method performs similar to or in some cases better (when detecting spurs than current terrain features detection methods, such as geomorphon, curvature, and probabilistic methods.

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