某长输埋地管道由于受外界干扰、防腐蚀层破损等原因，管道阴保电位出现欠保、过保及异常波动的现象。采用Fluke数字万用表、直流电压梯度测量法(DCVG)等埋地管道非开挖无损评价技术(NDE)，对阴极保护系统进行了全面检测和诊断。结果表明，管道沿线测得的阴保电位有些超出了阴保电位准则范(-850~-1 200 mV,CSE); 有些管段阴保电位频繁异常波动; 防腐蚀层检测出多处破损点，而且部分腐蚀活性呈阳性。研究发现，某混凝土穿越段采用套管保护，管道沿线周围存在电厂、电力铁路等，多处与埋地管线出现并行或者交叉情况。针对阴保电位屏蔽、杂散电流干扰等问题，提出了补加牺牲阳极、合理选择排流方式等解决措施。

Due to outside interference, coating damage and other factors, the cathodic protection potentials of pipelines are often less protected, over-protected and unusually fluctuate and so on. By using Fluke digital multi-meter potential measurement, DC voltage gradient measurement (DCVG) and pipeline current mapper (PCM) and other non-excavation of buried pipeline NDE techniques, a comprehensive on-site fault detection and diagnosis was done for the cathodic protection system for a long-distance buried oil pipeline. Besides, the located soil corrosion and the coating of the buried pipeline were tested and assessed. The results showed that the cathodic protection potentials measured from some potential test piles along the pipeline were beyond the cathodic protection potential criterion range (from -850 to -1 200 mV,CSE). Some cathodic protection potentials of the pipeline showed frequent abnormal fluctuations, multiple damage points of coating were detected, and some exhibited positive corrosion activity. The results showed that a section crossing under the concrete used the casing protection, high-speed rail and so on were built later and located nearby the pipeline, there was paralleling or crossing somewhere. The cathodic protection potential shielding, stray current interference and other issues were discussed, and reasonable drainage measures and sacrificial anode were proposed.