Abstract
In order to research the electromagnetic interference in buried oil and gas pipelines generated by the grounding current of a grounding electrode of Ultra High Voltage Direct Current (UHVDC) system, observation experiments of stray current and pipe-to-soil potential (PSP) in the pipeline were carried out. Monitoring devices were installed at two sites of the Dong-Huang oil pipeline before the commissioning of the Zalute–Qingzhou and Shanghaimiao–Shandong ±800 kV UHVDC projects. Monitoring data on the stray current and PSP of the two monitoring sites were obtained when the two UHVDC projects were operated in monopolar mode on 24 December 2017 and 2 January 2019 and the grounding current reached 6250 A. The amplitude characteristics of the stray current and PSP at different distances from the grounding electrode and the effects of the magnitude of the stray current and PSP on the cathodic protection system are analyzed herein. The results show that the effects of the grounding current on pipeline corrosion are not only closely related to the distance between the grounding electrode and the pipeline but are also related to the running state of the potentiostats of pipelines and the distance between insulation flanges. Optimizing the performance of potentiostats and the distribution of insulation flanges can reduce the effects of UHVDC grounding current on pipeline corrosion.
Highlights
Because Ultra High Voltage Direct Current (UHVDC) systems and long-distance oil and gas pipelines are important facilities [1,2], more and more attention has been drawn to the safety of UHVDC and oil and gas pipelines
According to the mechanism of pipeline corrosion caused by a stray DC current and the principle of cathodic protection, the main conclusions of this paper are as follows: (1)
The monitoring results show that the pipe-to-soil potential (PSP) offset of the pipeline 150 km away from the grounding electrode will exceed the limit of the drainage standard, due to the large grounding current of the high-power UHVDC project
Summary
Because Ultra High Voltage Direct Current (UHVDC) systems and long-distance oil and gas pipelines are important facilities [1,2], more and more attention has been drawn to the safety of UHVDC and oil and gas pipelines. When the PSP offset exceeds the standard or when the cathodic protection systems fail to operate effectively, the stray current generated by the grounding current will accelerate corrosion, reduce the service life of pipelines, and even cause explosions which may lead to heavy casualties and economic losses [6,7]. The results show that the resistivity of the insulating coating is an important factor determining the corrosion of a pipeline; the buried depth of the grounding electrode has no influence on the corrosion of a pipeline [9]; and the magnitude of the Energies 2019, 12, 1279; doi:10.3390/en12071279 www.mdpi.com/journal/energies. The corrosion of a pipeline grounding resistivity, andcorrosion the distribution of insulation coating defects have a varies great with the on magnitude of the grounding hydrogen evolution corrosion when influence the corrosion of pipelines [6].
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