Distribution of Potential in the Ground after the Fall of a Railroad Overhead Wire

This study considers the potential distribution in the ground when a railroad overhead wire falls onto the ground. It is shown that, in the case of direct current, the distribution of the potential and voltage at a growing distance from the source is sharply uneven and the nature of the unevenness changes over time. The high temperature at the point at which the wire falls, leads to the ground near this zone exhibiting minimal specific resistance; this causes further preferential heating of the near-contact area. In the case of direct current at a high temperature coefficient of resistance and a positive ambient temperature, the latter has almost no influence on the values of the potential and the current density. Negative ambient temperatures result in high electrical-potential values. In the near-contact region, however, the potential changes in a smoother manner, which leads to lower field strengths and current densities in this region. With growing distance from the contact point, the most dangerous temperature range is from −2 to 0°C, a range that leads to high electric-field strength and potential values. At an alternating voltage, the temperature distribution deep into the ground from the point where the wire has fallen is extremely uneven, and this unevenness increases even more over time. An increase in the moisture content in the ground causes a sharp increase in the field strength and current density in the near-contact region. However, in areas far from the wire-fall point, these values are slightly higher in a dry environment than in a wet one.