Influence of HVDC Transmission Line Grounding Electrodes on Natural Gas Pipeline Networks and Pipeline Corrosion Behavior

The Shanghai natural gas trunk pipeline network is located within a closest distance range of 3.5-9.0 km from the Yaojing, Langxia, and Nanqiao grounding electrodes of high-voltage direct current (HVDC) transmission line. A remote potential monitoring system was employed to conduct continuous potential measurements on typical interferend pipeline sections close to the grounding electrodes, while corrosion coupons were used to determine the corrosion rates of these sections. Based on the remote potential monitoring results and coupon test data, the interference of the HVDC grounding electrodes on the buried pipeline and the associated corrosion behavior were analyzed. The results show that during HVDC grounding electrode discharge operations, pipe-to-soil potential shifts occurred in all pipeline sections. The potential shifts in pipeline segments close to the grounding electrodes were significantly greater than those in sections farther away. The interference of HVDC grounding electrodes on pipelines became more concentrated as the distance between them decreased. The conduction of HVDC grounding electrode interference current through adjacent pipelines enhanced its effects on remote pipelines, thereby modifying both the interference characteristics and distribution range. Under monopolar discharge of HVDC grounding electrodes, the larger the damaged area of the pipeline's anti-corrosion coating, the lower the interference current density, and the lower the pipeline corrosion rate.