AC Voltage Mitigation

AC Voltage Mitigation

Problem:

When pipelines are in a common corridor with energized power lines, electric and magnetic fields can cause unwanted voltage to appear on the pipeline. Induced AC voltage can create safety hazards and contribute to corrosion problems. To address these problems, this induced voltage requires low resistance grounding for mitigation, while cathodic protection demands complete isolation for the pipeline.

Solution:

Dairyland products provide continuous AC grounding for pipelines with induced voltage, while leaving the cathodic protection voltage unaffected. The device presents low impedance to alternating current and high impedance to direct current, and connects between the pipeline and a grounding system.

Mitigation designs for induced AC voltage are best done by specialists trained in the proper analysis techniques. Such analysis involves measurements and electrical modeling, using software developed for this task. While an overview of the issues involved is shown below, complete analysis may involve the use of such specialists.

Small projects can have reasonable estimates applied to determine product ratings and a basic system design. Examine the issues outlined below or call Dairyland for additional guidance.

To implement an induced AC mitigation system, the following issues need to be examined to determine product selection and ratings:

  1. A suitable low resistance grounding system is needed (designed by others)
  2. Select a decoupler AC fault current rating that is above the modeled or expected exposure at the site
  3. Model or measure the induced AC steady-state current available to flow to ground. Select a decoupler with an adequate rating.
  4. Determine if the location is classified as a hazardous location and select the appropriately certified decoupler type
  5. Choose a suitable mounting accessory, such as a pedestal or enclosure
  6. Consider a decoupler safety disconnection switch during testing

For a full review of this application, please review our technical article: AC Voltage Mitigation on Pipelines and Use of Decouplers