Detection for AC Stray Current Interference on Long-distance Natural Gas Pipelines

This document applies to the detection of AC stray current interference on long-distance buried steel natural gas pipelines. Pipeline operators and inspection entities shall investigate interference sources, including high-voltage transmission systems and electrified railways, as well as pipeline coating, cathodic protection and soil resistivity before testing; arrange measurement points; and use verified or calibrated instruments to measure AC interference voltage and current density, recording measurement times, locations and data. It specifies requirements for measurement frequency, periods, wiring and data processing, and evaluates interference severity by AC current density. Protective measures shall be taken for severe interference and medium interference that does not meet the specified conditions; following drainage protection, prescribed voltage or current-density limits shall be met.