eGruposDMime - Pipeline Safety Determining The Effects On...

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/February 2001/ www.undergroundinfo.com A major concern for the pipeline operator is determining how to test, monitor and maintain pipelines built in a power company's trans- mission right-of-way (ROW). In addition, there are a number of safety precautions that should be adhered to whenever tests are being conducted in a joint facility. To lower electrical interference effects to pipelines in close proximity to electric trans- mission cir- cuits, the pri- mary method is by reduc- ing the pipeline resistance to earth. This is accom- plished with electrical interference mitigation systems installed at areas of peak AC or DC volt- ages along the pipeline. In addition, in order to maintain safety under fault con- ditions, gradient control mats are installed at aboveground appurtenances where contact with the pipeline can be made. The lowering of the pipeline's resistance to earth, however, can affect the opera- tion of a cathodic protection system on the pipeline. Interference Mitigation Systems There are a number of different sys- tems used for mitigation of electrical inter- ference on aboveground and buried struc- tures. These include zinc ribbon anode material, packaged magnesium anodes, carbon steel, galvanized steel and bare copper wire. Some of these methods, including the zinc ribbon and the pack- aged magnesium anodes, can be used for cathodic protection and mitigation of electrical interference on the pipeline. Use of the other methods of interfer- ence mitigation requires the isolation of the pipeline from the grounding system to reduce cathodic protection requirements and maximize current distribution. Isolation devices such as zinc grounding cells, polarization cells, and solid-state isolator-surge protectors are used to iso- late the pipeline from the grounding sys- tem and to protect isolated fittings from lightning and other electrical interference damage. These devices are considered a part of these mitigation systems and require monitoring and maintenance. Electrical Interference Mitigation Testing When testing electrical interference mitigation systems in joint corridors a number of safety and equipment issues are of concern. If these measurements are not conducted correctly, the interaction of a cathodic protection and electrical inter- ference systems can produce field meas- urement data that is not consistent with data recorded in areas without the influ- ence of high voltage electric transmission lines. This data may indicate that areas of the pipeline system do not comply with minimum state and federal regulatory cor- rosion control requirements. These measurements must be taken properly, the appropriate criteria applied, and each measurement evaluated. These activities are performed to maintain pub- lic safety, and reduce operating costs from electrical interference. Proper training, well-documented measurement proce- dures, and an automated record keeping system can address these challenges
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This note was uploaded on 08/25/2011 for the course CHEM 101 taught by Professor Krull during the Spring '07 term at Northeastern.

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eGruposDMime - Pipeline Safety Determining The Effects On...

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