Geomagnetically Induced Current - GIC Hazard in Pipelines

GIC Hazard in Pipelines

Major pipeline networks exist at all latitudes and many systems are on a continental scale. Pipeline networks are constructed from steel to contain high-pressure liquid or gas and have corrosion resistant coatings. Weathering and other damage to the pipeline coating can result in the steel being exposed to moist air or to the ground, causing localised corrosion problems. Cathodic protection is used to minimise corrosion by maintaining the steel at a negative potential with respect to the ground. The operating potential is determined from the electro-chemical properties of the soil and Earth in the vicinity of the pipeline. The GIC hazard to pipelines is that GIC cause swings in the pipe-to-soil potential, increasing the rate of corrosion during major geomagnetic storms (Gummow, 2002). GIC risk is not a risk of catastrophic failure, but a reduced service life of the pipeline.

Pipeline networks are modelled in a similar manner to power grids, for example through distributed source transmission line models that provide the pipe-to-soil potential at any point along the pipe (Boteler, 1997; Pulkkinen et al., 2001). These models need to consider complicated pipeline topologies, including bends and branches, as well as electrical insulators (or flanges) that electrically isolate different sections. From a detailed knowledge of the pipeline response to GIC, pipeline engineers can understand the behaviour of the cathodic protection system even during a geomagnetic storm, when pipeline surveying and maintenance may be suspended.