| Summary: | 碩士 === 國立高雄應用科技大學 === 機械與精密工程研究所 === 99 === Alternating current corrosion had not been taken into account until two pitting corrosion of a PE coated pipeline were found in West Europe in the ‘90s. It was proven that an AC transportation system created AC corrosion in forms of pitting on the underground pipeline. Therefore, intensive studies on the corrosion of AC current on buried structures grew up in the recent years. Even though theories and corrosion control methods for AC corrosion have been proposed in the several researches, lack of knowledge in this field is still present in Taiwan railway system communities and workers. This paper is an attempt to remind the Taiwan railway system communities and workers of that AC corrosion on underground steel structure is quite universal also serious. The traditional cathodic protection technology will not control AC corrosion to acceptable levels even fail so that it must simultaneously solve AC corrosion problems to maintain the underground steel structure integrity. Their traction power system use steel-wheel-ails as current return path, because of inherent resistance of rail, there exits a voltage along the railway track, and a potential between railway and ground ,called railway-to-ground-potential which will be transferred by the rail to car-body form touch-voltage .Because the rails are not fully insulated from the ground , a portion of traction current will leak into ground via running rails , called stray current . According to the different types of grounding, the touch-voltage causing by the rise in rail potential would cause different degree of damage to human body. Similarly, according to the different types of grounding, the stray current will flow more or less via running railways into metallic pipelines, rebar in reinforced concrete main structure buried underground and to the traction power station finally. Then , the damages on equipments and hazards on human due to ground faults are assessed based on relational standard, and causes problem of electro chemical corrosion and damage track facilities , metallic structure buried underground and others railway system facilities . This study will simulate the stray currents with respect to the corrosion effects on metallic structures are also evaluated. Finally, the mitigation methods for reducing stray current damage are proposed. Thus, the study provides useful information to THSR and TRA to design their underground structure grounding systems and power returning systems for reducing damages caused by the stray current.
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