Case Study on Interference Effect of DC Stray Currents on Natural Gas Pipelines
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Abstract
Using test piece power-off method and potential monitoring system, 24 h on/off potential detection and long-term monitoring of a natural gas pipeline in Guangdong area were carried out, and it was found that there was obvious direct current (DC) stray current interference in the pipeline. The potential detection and monitoring results show that the natural gas pipelines in Guangdong had unbalanced current, single-maximal loop current and subway stray current interference. Due to the interference of DC stray current, the tube segment was ablated, the internal components of potentiostat were burned out, the potentiostat could not operate normally, and the tube corrosion occurred at different positions of the pipeline. The corrosion depth of the pipe with the most serious corrosion reached 3.69 mm. In this position, the pipe was disturbed by the pipeline in the single-maximum operation mode of high-voltage direct current (HVDC) grounding transmission system, and the pipeline potential could reach -174.6 V. At the same time, due to the superimposed interference of the unbalanced current of HVDC transmission system and the stray current of subway, the pipeline was in an under-protected state for a long time, and the combination of several factors caused the corrosion of this section of the pipeline to be severe.
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