Interference Effects of Ultra-High Votage Direct Current Grounding Current on Cathodic Protection of Buried Steel Pipeline

A pipeline and Gongle grounding electrode of ultra-high voltage direct current (UHVDC) in Sichuan-Chongqing area were selected as research objects. The cathodic protection parameters of the pipeline during discharge of the grounding electrode were continuously monitored by cathodic protection test technology. The interference range and influence degree of UHVDC grounding current on the pipeline were analyzed. The results showed that the polarization potentials exceeded the standard in 11 places throughout the pipeline during cathode discharge of the grounding electrode with 2 900 A. The most negative pipeline potential was -3 347 mV, and the most positive pipeline potential was +189 mV. The pipeline with a positive potential offset more than 100 mV was about 28 km in length, and the UHVDC grounding electrode discharge had a wide range of influence. Corrosion protection measures such as potentiostat and zinc strip played positive roles in alleviating and restraining stray current interference in the discharge process of the grounding electrode, but there were still corrosion risks at the damaged points in some pipe segments. Finally, the corresponding suggestions were proposed according to the situation of pipeline cathodic protection and test results.