Reduction of the electrical potential of interfered pipelines due to currents of high voltage power lines and electric railways

Inductive interference of natural gas-, oil-, district heating- and water-pipelines due to short circuit and operation currents of high voltage lines and electric railways is a noticed problem since influencing and influenced systems are constructed very close together in the same so called "energy route". The measurement of the pipe potentials against remote earth at defined pipeline locations as well as the calculation of the induced voltage along an interfered pipeline is very important to identify critical sections on the pipeline to reduce the risk of hazard on the one hand and the a.c. corrosion possibility on the other hand. A.c. corrosion, which already begins at induced voltages in the range of 4–10 V depending on the specific soil resistivity can lead to pipeline leakages in worst case. This paper delivers some insights into an actual interfering situation regarding a new built 400 kV overhead line and an existing natural gas pipeline. The methods of measuring and simulation are described separately. Afterwards the results are compared and discussed. Finally, common potential mitigating measures such as a.c. earthing systems and galvanic separations by insulating joints in the course of the pipeline, as well as some alternative measures like the connection to low impedant operational earths of in Austria applied low voltage TN-systems and the use of surge arrestors, are shown.