Judgment of interference index of buried AC gas pipeline

AC stray current is the most direct reflection of AC interference and corrosion of buried steel gas pipeline by electrified railway. However, due to the limitation of practical conditions, AC stray current of electrified railway cannot be measured directly. Therefore, the main criteria for the corrosion degree of pipeline under interference are pipe ground potential difference and soil potential gradient, which is called electrical discrimination method. The stray current is the most important parameter to reflect the corrosion characteristics of the pipeline.



Without increasing the current source, the increase of pipe to ground potential is the sign of stray current entering point, and the decrease of pipe ground potential is usually the indication of stray current discharge point. When the pipe ground potential is unstable, the pipe ground potential seriously deviates from the normal value or the soil potential gradient is abnormal, it indicates that there is stray current, and the stray current inflow, outflow points and current magnitude can be analyzed through the soil potential gradient.



For the electrified railway, the pipe ground potential changes randomly with the train load, and the pipe ground potential alternates violently when the locomotive is running, but the fluctuation may be obviously weakened at night. The interference of cathodic protection system is relatively stable. Therefore, the change of pipe ground potential caused by cathodic protection system is also stable. When the locomotive is stopped, the interference disappears. Therefore, whether the buried pipeline is disturbed or not is usually judged by the change of pipe ground potential.