Pipeline AC Interference and Mitigation

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.