The quality of the indirect inspection data is a critical factor in conducting a successful ECDA program.
New NACE standards (SP0207-20071 and TM 0109-092), improved instrumentation, experience sharing,
and extensive training during the last several years, has resulted in a significant improvement in the accuracy
of the survey data.
This paper covers a number of lessons learned by dealing with less-known sources of measurement
error, during six years of ECDA application on more than 50 gas pipelines in Ontario.
Topics addressed include a discussion of errors:
• generated by rectifying elements in current interrupters,
• caused by the influence of remote rectifiers,
• introduced by local changes in soil resistivity during the DC Voltage Gradient Survey, and
• produced by transient currents during the Close Interval Potential Survey.
Keywords: ECDA, CIPS, DCVG, HVAC powerlines, influence survey, transient currents