Title : Electrical power sources impact on oil & gas buried pipeline integrity
Abstract:
Pipeline leaks are one of the most critical issues that companies in the oil and gas industry must address. The primary cause of pipeline leaks is corrosion in either the interior or external parts of the pipeline. Companies have made significant efforts to combat equipment failure due to rust. Corrosion cannot be eliminated, however it can be mitigated. Cathodic protection has been widely used to protect the pipeline's externally parts.
In cathodic protection, the term “interference” is understood in the pipeline industry as electrical interference and is defined as “any detectable electrical disturbance on a structure caused by a stray current where a ‘stray current’ is defined as a current in an unintended path”. Furthermore, although the interfering current is often a direct current (DC) from a cathodic protection (CP) impressed current source, the current can also originate from any electrical system that uses the earth either intentionally or inadvertently as a current path. Thus alternating current (AC), solar Photovoltaic (PV) system and high voltage Direct Current (HVDC) can be included in the definition.
The location of steel buried pipelines in the vicinity of AC power transmission facilities has resulted in mutual electrical interference problems that can produce damaging effects on both utilities and an electrical hazard to pipeline personnel. However, the vast majority of interference problems is created by three-phase power transmission systems, since these involve both high currents (steady-state and fault conditions) and high voltages and are more likely to parallel pipelines for long distances than are low voltage distribution systems, for instance. Electrical energy from an overhead power line can be transferred to a pipeline by three possible mechanisms—conductive coupling (during fault conditions), electrostatic or capacitive coupling, and electromagnetic or inductive coupling.
Moreover, Due to the continuous growth of energy consumption and the installation of solar photovoltaic arrays at facilities and along the pipeline right-of-way (ROW) are being considered to reduce the carbon footprint, this close proximity has become more and more frequent. Therefore, there is a growing concern about the possible hazards resulting from the influence of DC leakage of grounded solar photovoltaic on metallic buried pipelines. The effects of DC stray current on metallic structures can be harmful, beneficial, or innocuous depending on the magnitude of the current density, type of structure, and location of current pick-up and discharge areas.
The prime objective of the presented work is to study the electrical interference taking place between power line and buried pipeline by focused on calculations of the induced voltage on pipeline and the mitigation design techniques using a developed MATLAB M-file program designed by the author, to examine the interference at both steady state and during fault conditions and compare results with applicable standards and to evaluate the performance of the earthing / grounding method when used for mitigation of induced voltages on pipelines.
Furthermore, impact of DC stray current corrosion from PV systems will be illustrated by estimating the local pipeline’s potential shift at the coating / electrolyte interface based on the coating defect size and soil resistivity along the pipeline allows for the quantification of the corrosion risk on coating defects and will be compared against the allowable threshold limit based on international standards. The results and conclusions presented here can be used as a reference to analyse the severity of DC interference on pipelines due to proximate PV systems.
Finally, conducting these simulations and study will provide increased confidence when undertaking mitigation design by highlighting interference hot spots, therefore assisting with the design of more efficient mitigation systems to address both personnel safety and pipeline integrity concerns.
Audience Takeaway Notes:
- Will illustrate the impaction of DC &AC interference on buried pipeline integrity.
- Does this provide a practical solution to a problem that could simplify or make a designer’s job more efficient? Yes, absolutely will make a designer’s job more efficient.
- Will improve the interference mitigation methodologies.
