Electrical Circuit for Off-Potential Measurement without SSD

Electrial Circuit of Pipeline without SSD for Off-Potential Measurement

Electrical Circuit for Off-Potential Measurement with SSD

Electrial circuit of Pipeline with SSD for Off-Potential Measurement

What Happens while Measuring Off-Potentioal with SSD Connected

• When CP current (S1) is interrupted:
• The voltage across decoupler must change by the Icp x Rp voltage drop component that was eliminated
• A transient current must flow to make this voltage change
• Until this transient current is dissipated, an Off Potential measurement will not be measured accurately(too electronegative).

How to Measure Off-Potential with SSD

• OFF waveform analysis with a longer than normal On-Off cycle (e.g. 7 On, 3 Off)
• Determine the time after current interruption where a stable Off potential is reached
• Increase the measuring delay time according, if possible
• On some pipeline, increasing the measuring delay time will not be an option and this will be evident from the waveform analysis.

Reference

Dairyland Electrical Industries Technical Blog