Abstract
Space weather results in risks to gas pipelines in the form of both hazardous levels of pipe-to-soil potentials during extreme geomagnetic storms, and accumulated corrosion through less severe, but continuous geomagnetic activity. Here we report on calculations of pipe-to-soil potentials during a simulated extreme storm, using both direct pipeline modeling and based on transfer functions between magnetic field variations and observed pipe-to-soil potentials. Potentials exceeding +/- 500 V, which may cause damage to the cathodic protection system, are not seen at any location although large, short period spikes in potential are calculated to occur at three sites. Lower levels of potential exceeding +/- 50 V, which may be hazardous to personnel, occur at several locations. For those sites, where very large potentials are calculated to occur, they are seen to exist for considerable lengths of time. The transfer function technique, allied with relationships between pipe-to-soil potentials when the cathodic protection system is on/off, and between pipe-to-soil and installed coupon potentials, are used to calculate the lengths of time, during multiple magnetic storms of different intensity, when potentials exceed recommended industry levels for protection against corrosion. These times are converted to estimated annual corrosion rates. We find that these are only larger than recommended limits at three sites; at two of these the limit is only exceeded for small defects in pipeline coating. The other site is highly anomalous, possibly due to the effect of interference from the local rail network. The risk of pipeline coatings becoming detached from the pipe is low.