ABSTRACT: Recently, pipelines are being constructed in parallel with high voltage power lines due to industrial development. This results in AC interference which gets more and more attentions for leading to electric shocks and accelerating corrosion of pipelines. A mitigation system can decrease AC potential and AC corrosion. Design of a mitigation system is complex. The effects of the following factors on the mitigation system were studied: the number of connections between mitigation wires and pipelines, locations of mitigation wires and connections, orientation of mitigation wires (horizontal or vertical). The results show that installing mitigation at one place can increase the induced AC voltages in other place even separated by many kilometers. The induced AC voltages along the pipeline decrease with increasing connections. The locations of mitigation wires and connections have an effect on induced AC voltage peaks and the best locations for them are the positions with voltage peaks. Minimum interference level is achieved when mitigation wires are located at the side of power line around pipe. When the zinc (Zn) ribbon is shorter than 850 m, mitigation effectiveness of vertical Zn ribbons are better than that of horizontal ones. Above 850 m, horizontal Zn ribbons are better. These results can provide the readers with suggestions that make the design of mitigation system more effective and more economical.
INTRODUCTION With the rapid development of electricity, petroleum and transport industry, more and more pipelines are buried in parallel with high-voltage transmission lines or electrified railways in recent years. Furthermore, AC corrosion due to AC current that escapes the pipe can also result in failure and leak of pipelines. Buried pipelines provided with high resistance coatings are more susceptible to AC interference. Numerous pipeline failure cases due to AC interference are reported in America, Germany, Canada, Australia and China.2-5