Off-Potential Interference by Solid State Decoupler

Electrical Circuit for Off-Potential Measurement without SSD

Electrial Circuit of Pipeline without SSD for Off-Potential Measurement

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

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

 

2 Comments

  1. Q

    quick interesting. something never thought about before

    Reply
  2. Xu

    Hello, I can’t watch the training video about “Decoupler Interaction with Close Interval Surveys” on youtube due to Chinese network restrictions. Could you send me this video by email? please. The website is http://www.dairyland.com/knowledge-base-article/34-video-training/31-decoupler-interaction-with-close-interval-surveys
    Thank you very much.

    Reply

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