Pipeline AC Interference and Mitigation

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Scene #1:
-Pipeline AC Interference & Mitigation
Scene #2:
-Steel pipelines and power transmission lines are often installed near each other in narrow corridors.
-This minimizes the impact on the communities around them and makes efficient use of the land.
-Using common land makes it easier to install, operate and maintain utilities. But, it can also lead to damage and hazardous situations due to AC interference.
Scene #3:
-AC current from transmission lines interferes with nearby pipelines through the following mechanisms:
· Inductive Coupling
· Resistive (or Conductive) Coupling
· Capacitive Coupling
Scene #4:
-Inductive Coupling occurs because AC current induces a voltage in adjacent conductors.
-Thus, normal operation of transmission lines creates voltage gradients in pipelines installed nearby.
-The induced voltages in the pipeline cause corrosive processes to occur faster.
-Induced voltages also create a hazard for service technicians who need to maintain and repair the pipelines.
Scene #5:
-Resistive coupling only occurs during fault conditions. For example, damage from a lightning strike may direct current through the grounding structure.
-The increase in ground current causes the electrical potential of the soil to rise. Since the pipeline is in direct contact with the soil, its electrical potential also rises.
-While this is not a common occurrence, it can add to the AC induced voltage in the pipeline, thus increasing the corrosion and hazard potential.
Scene #6:
-Capacitive coupling only occurs when the pipeline is not touching the ground. Thus, capacitive coupling happens on pipelines installed above-ground, or on pipelines resting on skids before installation.
-When the pipeline is above-ground, it is electrically-isolated. So, there is a voltage difference between the AC power lines and the pipeline.
-The voltage difference increases the risk of arcing. Arcing is a hazard for nearby vehicles, for example, where the fuel might ignite.
Scene #7:
-There are several mitigation strategies that can reduce the effects of AC interference.
-Increasing distance between transmission lines and the pipeline decreases the magnitude of interference.
-Where space is limited, providing paths for current to escape along the pipeline ensures that voltage does not build up in the pipeline.
-Many components are available to manage the current in a pipeline system, and therefore mitigate AC interference. Some of these are DC decouplers, surge protectors, grounding cells and galvanic anode installation cathodic protection systems.
Scene #8:
-Computer modeling programs are a key component of AC interference mitigation strategy. With modeling programs, we can visualize problems and solutions along the entire system.
-Used by trained engineers, these mitigation strategies are effective in protecting pipelines from AC corrosion caused by nearby power lines.
Scene #9:
Got a complicated pipeline project that requires sharing land with power transmission lines?
Allied Corrosion Industries, Inc. has worked on many long-distance pipelines, requiring both cathodic protection and AC interference mitigation strategies to ensure long life of these assets. Inquire today about design for your project.