Manage pipeline integrity by predicting and mitigating HVAC interference

Sharing of common corridors by gas pipelines and overhead power transmission lines is be-coming quite common. However, electrical energy can be transferred from power transmission lines to pipelines through inductive, conductive and capacitive coupling. When a power transmission line runs in parallel with a pipeline for a considerable length, induced AC voltages may appear on the pipeline.

While there are significant benefits in sharing a corridor between pipelines and power trans-mission lines, e.g. joint land use, there are also many concerns. The main ones are safety considerations for operation and maintenance personnel on pipelines, direct effects on the pipeline, such as corrosion and coating damage and effects on the electrical devices associated with the pipeline related to cathodic protection, metering and monitoring. AC induced corrosion is a significant threat to integrity of buried pipelines, due to its very high localized corrosion rate which can and has resulted in metal loss of more than 1 mm per year. AC corrosion mainly occurs at small coating holidays on well coated pipelines when the pipeline suffers from induced ac voltages.

In this paper, both the transmission line model (“far field” approach) as the more elaborated “close field” approach in which the resistive effect of the soil and discrete and continuous grounding systems can be modelled will be discussed.

Practical results of simulations on different configurations will be presented and compared with available experimental data for both the design and mitigation stage.