A high impedance fault (HIF) normally occurs when an overhead power line physically breaks and falls to the ground. Such faults are difficult to detect because they often draw small currents which cannot be detected by conventional overcurrent protection. Furthermore, an electric arc accompanies HIFs, resulting in fire hazard, damage to electrical devices, and risk with human life. This paper presents an analytical model to analyze the interaction between the electric arc associated to HIFs and a transmission line. A joint analytical solution to the wave equation for a transmission line and a nonlinear equation for the arc model is presented. The analytical model is validated by means of comparisons between measured and calculated results. Several cases of study are presented which support the foundation and accuracy of the proposed model.
A high-impedance fault is generated when an overhead power line physically breaks and falls to the ground. Such faults are difficult to detect and locate in electric power systems because of the small currents and voltage drops involved, which cannot be detected by conventional protection. Furthermore, arcing accompanies highimpedance faults, resulting in fire hazard, damage to electrical equipment, and risk to human life. This article presents an analytical description of the interaction between the electric arc associated with high-impedance faults and a transmission line. A joint analytical solution to the wave equation for a transmission line and a non-linear equation of the arc model is found for the case of an arbitrary reflection coefficient at the substation end, and a methodology for high-impedance fault detection and localization is proposed. The developed model is validated by means of a comparison with measurements. The comparison demonstrates the accuracy and effectiveness of the proposed model.
This paper shows the application of the electrochemical noise (EN) technique in the corrosion study on carbon steel in a salt-spray test. Through this electrochemical technique the resulting corrosion process is analyzed by the characteristics of the EN signal. These results, achieved with a statistical analysis of the signal, which is related to the wire-on-screw test, show the electrochemical differences in uniform, pitting, and crevice processes.
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