Conductor Design and Use for Power Transmission Applications

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Goal

  • Technical
    • Provide an optimized solution that :
      • Increases line capacity / ampacity (1.5 to 2.5X)
      • Maintains or reduces sag and tension
      • Meets stringent sag / clearance requirements that could not be met by other solutions (river crossings - cruise lines)
  • Value Proposition :
    • Reduce cost and risk by eliminating the need for :
      • New Right of way
      • Special permitting
      • Building new towers / structures
      • Modifying existing towers

Detail

The following are steps adopted to initiate a project with utilities. Input information accuracy (questionnaire) is the most critical step because all designs are based on it and if done correctly will save time and money. It is often updated, corrected because many times it is furnished by non transmission engineers. The whole approach is a team effort among utilities, manufacturers, designers, and application engineers.

Transmission Line Input Questionnaire

The following information request covers the essential data needed to start the conductor design/ evaluation and recommendation process.

 

Conductor Design and Selection Software

There are numerous analytical packages in the market that address transmission line design and performance. The ones that were used in this project are :

  • PLS- CADD (from Power Systems Inc. in Madison, WI)

     

  • Sag 10 (from Alcoa Co.)

     

  • Rate Kit (from the Valley Group Inc. in Hartford, CT)

     

  • Special in house custom written programs

     

Examples of designed conductor and its predicted performance

The conductor examples (summary) shown here were designed and fabricated on a custom needed basis. Design details are not addressed here but they are extensive and account for both electrical, mechanical, and thermal properties and field needs.

1 - Replace Bundled ACSR (aluminum conductor steel reinforced) with a single higher performance conductor (ACCR) with double the ampacity at nearly the same sag and tension. This eliminates the need to raise or upgrade the transmission towers producing huge cost savings.

2 - Increase Ampacity by replacing existing conductor with same size high performance one.

Increase Ampacity & lower sag using smaller conductor of lower cost (comparable corrosion resistance)

PLS-CADD Verify Sag - Tension - Line Clearance For Violation (Ampacity doubled using high performance type of conductor); Blue is ACCR Ostrich (300 kcmil), Red is Wolf ACSR (336.4 kcmil)- Same tension- lower sag- Line profile shown here is a portion of the actual line analyzed (line is > 100 Km)

 

Method

Maximum Ampacity, amps

Maximum Horizontal Tension, Lbs

Maximum Sag, ft

Inhouse

NESC

240C

2020 (0.5. 0.5)

10058

3319

35

45.2

Sag 10

NESC

240C

10034

3326

35.06

45.15

Plscadd

NESC

240C

2040 (0.5, 0.5)

10028

3318

35.18

45.34

 

Conclusions

Congested and thermally limited transmission lines performance can be upgraded using higher capacity conductors. This project shows the approach used to design these conductors and predict their performance.

Sag 10 is another analytical tool used to predict conductor performance (sag, tension and ampacity). Data from this software are not included here so as to reduce file size but could be provided if need.

Line - design applications involve practically acceptable analysis approaches and are not perfect tool. Therefore after installation line monitoring is needed to verify design predictions and find out how close such designs are to real life situation. It is always beneficial to compare results from more than one line design software. The following table summarizes predicted performance of conductors using three methods (software); very good agreement is seen among these methods. NESC refers to National Electrical Safety Code condition.

PLSCADD Use

The advantage of using Plscadd is that it predicts the conductor performance for the whole transmission line that is under consideration for upgrading. It shows regions which could potentially violate clearance above ground and may reveal other potential problems affecting performance and safety.



To see the resume of the expert associated with this case study, see the link below.

Resume of GYE Electric Power Transmission Line Expert Consultant

800.367.5524

 

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