Electrical Circuit for Off-Potential Measurement without SSD
Electrical Circuit for Off-Potential Measurement with SSD
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.
Dairyland Electrical Industries Technical Blog