Research on the corrosion effect of the UHVDC ground electrode current on the metal pipelines

In recent years, with the advantages of long distance and large capacity, ultrahigh voltage direct current (UHVDC) transmission projects are developing increasingly in China. Also UHVDC transmission projects share corridors with underground oil & gas pipelines has become increasingly prominent. UHVDC ground electrode influences underground oil & gas pipeline is a new problem in China with rapid development of the electric power and oil-gas industry. When the UHVDC transmission system is working under mono-pole ground return operation mode, a high magnitude ground current will be injected into the soil through the ground electrode. The injected current will cause corrosion effect on the underground metal facilities such as oil & gas pipelines around the UHVDC ground electrode. In this paper, the influence of the ground return current of the UHVDC ground electrode in mono-pole ground return operation mode on the metal pipelines around the UHVDC ground electrode has been studied. The electrolytic corrosion principle of the underground metal pipelines caused by the ground electrode current was discussed. Then several protective measures were elaborated in detail. The research can give useful guideline to the corrosion influence of the UHVDC ground electrode current on the metal pipelines and can provide protective measures for the metal pipelines. It can also be applied in design, planning and site selection periods for new UHVDC ground electrode.