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Resistance coupling mainly occurs in the grounding body near the strong streamline of the pipeline. Due to the large fault current, hundreds to thousands of amperes of current enter the ground through the grounding body, forming a strong electric field around the grounding body, which may cause the arc to burn through the pipeline, damage the anti-corrosion insulation layer, and breakdown the insulating flange and cathodic protection equipment.
In rural two line one ground power supply system, grounding electrode is the channel of working current. When the pipeline is close to the grounding electrode, the metal pipe itself has good conductivity, which provides a low resistance channel for its working current, which will make the pipe wall burn for a long time and seriously threaten the safety of the pipeline.
When high pressure acts on the defect part of pipeline coating, the arc will be formed. When the current reaches a sufficient amount and continues to flow for a long time, it will cause the pipe to melt. If the distance between grounding device and steel pipe is very small, it may directly lead to arc breakdown, which is equivalent to high current and coating steel pipe limiting transfer arc point. Arc action is concentrated in a small area, increasing the risk of melting.
For the protection of resistance coupling, it is mainly to increase the distance between the pipeline and the grounding body, and take corresponding protection measures to prevent the harmful impact of lightning and fault current on the pipeline, so as to protect the safety of the pipeline and human body. These measures include connecting grounding battery in series between pipeline and transmission line grounding electrode, grounding battery, lightning arrester, diode protector or polarized battery in series on both sides of insulation flange. Their common feature is that they do not affect the cathodic protection of pipelines.
Shandong Linyi Bosi conductive materials Co., Ltd. is a high-tech enterprise specializing in the production of MMO flexible anode, conductive polymer flexible anode and titanium coated anode, mainly providing cathodic protection technology, engineering design, installation and technical services. Tel: 0539 3712117, 15588026668.