Specially designed rectifiers capable of operating in off-potential mode have been operating successfully for more than two years in the Greater Copenhagen Natural Gas1 distribution system. The rectifier system is based on a conventional transformer rectifier operating in potential mode and a PLC controlled off-potential measurement and feed-back procedure. The IR drop is fed to the rectifier feed back loop hereby offsetting the conventional potential control by this (IR) amount.

The parameters resulting from the above described system include on-potential, off-potential, rectifier current, IR-drop and the average coating resistance of the pipeline. Benefits include:

  • The off-potential facility has proved to effectively provide a reproducible measure of the average coating resistance enabling the operator to conduct instant investigations on cause of coating damages and to pursue any third party that might have caused coating or pipeline damage.

  • The remote controlled T/R system automatically produces measurements in the silent hours (where no DC traction systems are active) as required in stray current areas thereby saving the operator for inconvenient and costly working hours.

Subject
Electric current, Barriers, Voltage drops, Voltage, Reference electrodes, Pipelines, Natural gas, Constants, Rectifiers, Equipment, Electrical resistance, Damage, Electrode potential
Keywords:
cathodic protection, remote monitoring, coating resistance, off-potential, third party damage
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2010
Association for Materials Protection and Performance (AMPP)
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