PLS-CADD FAQ – Complete Guide for Beginners and Professionals

PLS-CADD FAQ – Complete Guide for Beginners and Professionals

The most comprehensive PLS-CADD question-and-answer guide for use in transmission line design, sag-tension calculations, tower spotting, plan & profile outputs, and NGCP/utility-compliant engineering.

Table of Contents

1. What is PLS-CADD?

PLS-CADD (Power Line Systems – Computer Aided Design and Drafting) is the industry-standard tool for overhead transmission line engineering. It integrates terrain modeling, conductor behavior, structure libraries, sag-tension calculations, and plan & profile production into a single platform.

2. How do I start a new PLS-CADD project?

  1. Create a new .cwd file (File → New)
  2. Import survey data (LiDAR, CSV, TXT, or DEM)
  3. Set alignment or import a KML route
  4. Define design criteria and environmental loads
  5. Input conductor, OPGW, and insulator data

3. What survey data formats does PLS-CADD accept?

PLS-CADD supports:

  • LiDAR LAS/LAZ files
  • XYZ or CSV point cloud files
  • DEM (digital elevation models)
  • Photogrammetry-based terrain models
ASCII Example (X, Y, Z):
355100.22, 1441200.41, 103.55
355110.90, 1441210.02, 104.12

4. How do I generate a terrain model (DTM)?

Use Survey → New Surface From Points. PLS-CADD will build a TIN (Triangulated Irregular Network). You can filter vegetation and non-ground points before generating the surface.

TIN Surface
    /\      /\       /\ 
___/  \____/  \_____/  \______ ground

5. How do I define the alignment?

You may draw the alignment manually or import KML/shape files. Assign stationing starting from 0+000 and define PIs (points of intersection).

Alignment Path:
(PI1)-----(PI2)------(PI3)-----Straight Section-----

6. What design criteria must be set?

Design criteria drive sag-tension, tower loads, and clearance checks. Input:

  • Wind and ice loads (ASCE 74 / IEC 60826)
  • Temperature cases
  • Safety clearances:
    • Ground clearance
    • Road/river crossing clearance
    • Building setback
  • Electrical requirements (blowout, phase spacing)

7. How do I input conductor and OPGW details?

Under Structures → Conductor Editor:

  • Diameter
  • Metallic cross-section
  • Weight
  • Modulus of elasticity
  • Thermal expansion coefficient
  • Creep behavior
Conductor ---- sag curve ---- Conductor
         \                  /

8. How does PLS-CADD compute ruling span?

PLS-CADD uses the standard ASCE formula:

LR = Σ(L³) / Σ(L²)

This equivalent span is applied to sag-tension calculations and everyday loading.

9. How does PLS-CADD compute sag?

Sag is based on:

  • Conductor mechanical properties
  • Temperature
  • Tension
  • Ruling span
Sag Curve:
Tower A                           Tower B
  /\                                /\
 /  \______________________________/  \

10. How does automatic tower spotting work?

PLS-CADD uses algorithms considering:

  • Minimum and maximum span lengths
  • Clearance constraints
  • Ground profile
  • Tower families and heights
Auto-Spotting:
T1      T2       T3           T4
/\      /\       /\           /\
--200m--260m--230m-----------300m---

11. What structure files does PLS-CADD support?

It supports:

  • PLS-POLE structures (.pol)
  • Tower models (.tow)
  • XML-based structure families

12. How does PLS-CADD calculate tower loads?

It evaluates:

  • Vertical load
  • Transverse load
  • Longitudinal load
  • Wind on conductor
  • Wind on structure
Load Tree:
       ↑ Vertical
       |
   ←—— Tower ——→ Longitudinal
       |
       ↓ Transverse

13. How do I generate Plan & Profile sheets?

Go to Reports → Plan & Profile. Choose template (NGCP, IEC, custom). PNP includes:

  • Tower locations
  • Span lengths
  • Sag profiles
  • Clearance points
  • Crossings (road, river, structure)

14. How do I export Bill of Materials (BOM)?

PLS-CADD generates BOM covering:

  • Conductor lengths
  • Insulator sets
  • Hardware fittings
  • Tower types and quantities
  • Foundation types and volumes

15. Can PLS-CADD export to Google Earth?

Yes. Use File → Export → KML/KMZ for visualization of alignment and structures.

16. What are the most common PLS-CADD errors?

  • Survey not aligned with centerline: Fix using coordinate shift tool.
  • Vegetation mistaken for ground: Apply vegetation filtering.
  • Ruling span error: Ensure spans belong to the same tension section.
  • Tower clash: Increase ground clearance or tower height.
  • Creep mismatch: Re-check conductor creep parameters.

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