Mahanagar Gas is a City Gas Distribution Company engaged in the distribution of Natural Gas in and around Mumbai City. MGL has around 415 km of commissioned steel pipeline network which is being protected by ICCP. These pipelines are coated with three layer polyethylene coatings. Rectifying the external interferences on pipeline network is a major challenge for pipeline operating personnel in order to maintain safety and integrity of their pipeline. This technical paper is based on study of one of such external interference which posed a threat to MGL’s steel pipeline network.

High Voltage Direct Current (HVDC) is a system for transmission of electricity over long distances. This system uses Direct Current (DC) for bulk transmission of electricity in contrast with the more common Alternating Current (AC) systems. HVDC is considered to be more effective to increase power grid delivery capabilities.

A part of MGL’s pipeline network is currently facing interference due to a HVDC power substation on the outskirts of Mumbai. This substation is being operated by State Government and is affecting around 145 kms of MGL’s steel pipeline network during its monopolar operation for transmission of electricity. This interference is creating multiple anodic and cathodic areas on pipeline network with the help of a high magnitude current entering and exiting from pipeline at multiple locations which are difficult to predict and rectify.

This technical paper will elaborate the concept of HVDC interference on steel pipelines. It will give a brief overview on the methodology adopted for identifying, monitoring and analyzing this interference phenomenon and will comment on the results of this analysis. It will throw light on a variety of technical challenges faced in dealing with this interference while operating a city gas distribution network in particular. And finally, it will discuss about possible remedial measures available and their effectiveness to curb this interference.

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