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Underground Pipelines Near Power Lines or Cables - Coordination Studies

Managing a Potential Electrical Safety Hazard

Pipeline system voltage hazards

Large scale metallic pipeline systems located in proximity to ac overhead power lines or cables can experience induced voltages, which may be hazardous to maintenance staff and the general public, as well as causing accelerated ac corrosion on the pipeline itself.

The magnitude of the induced voltage depends on the exposure length, the offset between the pipeline and power conductors, the current in each conductor (including overhead ground wires and cable sheaths) and the soil resistivity, which affects the depth of the earth return current. To accurately assess the voltage hazard, both load and fault conditions must be investigated. 
 
The current on faults can reach 10 to 50 kA, but with a relatively short duration (50 to 500 ms). For this condition, IEEE Std. 80 specifies the allowable step and touch potentials (200 to 400 V), depending on the surface soil resistivity.
 
Coordination study outline
 
Coordination studies by Kinectrics for underground pipelines compare these limits to the modelled step and touch stresses accessible by pipeline staff and the general public, for example, stresses found near valve stations or residential gas meters. These stresses occur due to soil potential rise close to the fault location, as well as induction from power conductors to the pipeline. The coating stress voltage under fault conditions in the event of a fault at various towers along the right-of-way corridor will also be studied to determine the maximum coating stress on the pipeline.   
 
Under normal load conditions, significantly lower induced voltages are present on the pipelines. Here, potentials exceeding 15 V are considered a hazard to technical personnel and the general public, along with the risk of ac corrosion on the pipes (CSA Std. C22.3 No. 6).
 

Hazard condition assessment

Performing multiple soil resistivity tests along the corridor, as well as accurately surveying power lines and locating underground pipelines, is essential for the modelling. To accurately calculate these voltages, Kinectrics models the pipeline, power conductors, and underlying soil measurements in detail, to review and document the various mutual coupling components.  
 

Kinectrics’ methodology is based on calculating mutual coupling components between various conductor segments of the model. For this purpose, Kinectrics uses the HIFREQ and Right-of-Way platforms from CDEGS software package (SES Engineering), which are capable of calculating inductive, capacitive, and conductive effects simultaneously. The results of the model are validated against simplified analytical formulas applied to the results of power flow studies to ensure the correctness of the model.  

Comprehensive expert studies 

Kinectrics’ comparison study deliverables include the determination of steady voltages on pipelines under normal load conditions, and short duration step, touch, and pipeline coating potentials during fault conditions.
 

Kinectrics’ experts compare these stresses to the industry standard allowable limits and can provide clients with effective mitigation options for achieving coordination to meet their specific needs. This assessment process ensures the safety of the maintenance crew and general public when in the vicinity of these infrastructures.

References:

  • CSA Standard C22.3 No. 6 “Principles and Practices of Electrical Coordination between Pipelines and Electric Supply Lines”, 2013 
  • “IEEE Guide for Safety in AC Substation Grounding", IEEE Std 80-2000 , vol., no., pp.i,192, 2000

 

 

 

 

About This Solution

Industry Sector

  • Transmission & Distribution

Nature of Service

  • Analysis
  • |
  • Consulting
  • |
  • Safety

Client Assets

  • Cables

Kinetrics Facilities

  • Mobile Electrical Test Facility

Tags

  • highvoltage
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  • underground cable
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  • Ontario
  • |
  • soil resistivity
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  • hazard assessment
  • |
  • pipeline systems
  • |
  • Voltage hazards
  • |
  • renewable energies
  • |
  • Safety
  • |
  • Toronto
  • |
  • Electromagnetic induction
  • |
  • capacitive
  • |
  • induction study
  • |
  • conductive
  • |
  • Modelling
  • |
  • wind farm