Risk and prevention measures for transferred voltage on external metal water pipes at power stations

Abstract

External metal water pipes of power stations are subject to a high risk of transferred voltage. Although global standards recommend inserting insulating sections, and some standards recommend insulating sections lengths of 9–10 m, research has found that this measure will fail in some conditions. This study investigates the risk of transferred voltage on external metal water pipes at power stations and analyses the effectiveness of inserting insulating sections where the pipes exit the stations. Through this investigation, the distribution characteristics of transferred voltage and the key factors to consider in designing prevention measures are obtained. The required length of insulating sections for typical buried pipes is determined. Moreover, the limitations of the conventional method of inserting an insulating section on overhead pipes for controlling the risk of electric shock are highlighted. This study proposes solutions for managing transferred voltage on overhead pipes by using pipe-to-ground insulation or segmented insulation techniques. The results indicate that the length of an insulating section (usually >10 m under low-resistivity conditions) required for buried metal pipes decreases with an increase in soil resistivity. When applied to overhead pipes, segmented insulation measures can help divide the pipe into several equipotential sections, thereby reducing the potential difference between the pipe and the ground and eliminating the risk of transferred voltage.