What Is PLS-CADD Modelling? Understanding it Inside Out
What PLS-CADD Actually Does: A Working Engineer's Guide to Modelling
You have probably watched a colleague click through a PLS-CADD model without fully grasping what happens behind the interface. The software name gets mentioned in project meetings, tender documents, and job adverts, but the actual mechanics of what it models and calculates remain unclear until you sit down with it yourself.
That gap between hearing about a tool and understanding what it does creates a real problem. You cannot decide whether to invest your time learning PLS-CADD, or whether your organisation should adopt it without knowing what it actually contains and what it replaces.
This guide covers what sits inside a PLS-CADD model, how it connects to PLS-POLE and PLS-TOWER, and what it calculates that traditional spreadsheets and hand methods simply cannot replicate.
What PLS-CADD Is and Who Builds It
PLS-CADD stands for Power Line Systems - Computer Aided Design and Drafting.
Power Line Systems, Inc., based in Wisconsin, USA, develops and maintains the software. The company has been refining it since the early 1990s, and it has become the industry-standard tool for overhead transmission and distribution line design worldwide.
The software handles the full design cycle: terrain modelling, structure placement, conductor stringing, sag-tension calculations, clearance checks, and loading analysis. It integrates directly with PLS-POLE for wooden and concrete pole analysis and PLS-TOWER for lattice steel tower design.
Unlike general-purpose CAD software, PLS-CADD is purpose-built for overhead line engineering. Every function assumes you are designing conductors suspended between structures across real terrain.
What Sits Inside a PLS-CADD Model
A PLS-CADD model contains four core elements that work together:
Terrain Data
The model starts with ground surface information, typically imported from survey data, LiDAR, or photogrammetry. This terrain forms the base layer against which all clearances are measured. You can import existing ground models or build terrain from survey points directly in the software.
Structure Locations
Each structure, whether a pole, tower, or H-frame, sits at a specific location along the line route. The model stores the structure type, height, attachment points, and orientation. You can move structures and immediately see how that affects spans, tensions, and clearances.
Cables And Hardware
The model holds conductor, earth wire, and optical ground wire (OPGW) properties. These include diameter, weight, breaking load, creep behaviour, and thermal expansion coefficients. The software calculates how each cable behaves under different temperatures, ice loads, and wind conditions.
Load Cases
This is where PLS-CADD differs most from simple drafting tools. You define the weather and loading conditions the line must withstand: everyday temperature, maximum operating temperature, ice loading, wind loading, and any combination required by your design code.
The software then calculates sag, tension, and clearance for every span under every load case.
PLS-CADD, PLS-POLE and PLS-TOWER: Which Does What
The three modules serve distinct purposes but share data seamlessly.
PLS-CADD handles the line as a whole. It calculates conductor sag and tension, checks clearances to ground and obstacles, and produces plan and profile drawings. It answers the question: "Where do structures go, and do conductors maintain required clearances everywhere?"
PLS-POLE analyses individual pole structures. When your line uses wooden poles, concrete poles, or steel monopoles, PLS-POLE checks whether each structure can withstand the loads from the conductors attached to it. It considers bending, buckling, and foundation reactions. PLS-CADD sends the calculated wire loads directly to PLS-POLE.
PLS-TOWER does the same job for lattice steel towers. It analyses the tower as a three-dimensional frame structure, checking each member and connection against the applied loads. Again, PLS-CADD automatically provides the conductor and wind loads.
This integration matters because changes in one module flow through to the others. If you adjust conductor tension in PLS-CADD, the updated loads appear in your PLS-POLE or PLS-TOWER analysis without manual re-entry.
What the Software Calculates That a Spreadsheet Cannot
Spreadsheets work well for single-span sag-tension calculations under one or two load cases. They struggle with real overhead lines.
Multi-Span Ruling Span Analysis
Overhead lines rarely consist of identical spans. Suspension insulators allow the conductor to move between spans, redistributing tension. PLS-CADD handles this automatically, calculating how tension equalises across multiple spans with varying lengths and elevation changes.
Simultaneous Multiple Load Cases
A design code might require you to check 15 or 20 different weather conditions. PLS-CADD calculates sag, tension, and clearance for every span under every load case in seconds. Doing this manually takes days and introduces transcription errors.
True 3D Clearance Analysis
Conductors blow sideways in the wind. Ground profiles change across the right-of-way. Obstacles like trees, buildings, and roads sit at specific coordinates. PLS-CADD checks clearances in three dimensions, accounting for conductor blowout and the actual position of obstacles.
Uprating Studies
When you need to increase the operating temperature of an existing line, PLS-CADD recalculates every clearance at the new temperature. It identifies which spans become critical and which structures might need to be raised or replaced.
Automatic Plan And Profile Generation
The software produces scaled drawings directly from the model, with conductor positions, ground profiles, structure details, and clearance annotations. These are updated automatically when you change the design.
A Worked Example: Modelling a Short 132 kV Line
Consider a simple project: a 2 km, 132 kV transmission line across gently rolling farmland with eight lattice steel towers.
Step 1: Import terrain.
You bring in LiDAR survey data covering the route corridor. PLS-CADD displays the ground surface as a 3D model.
Step 2: Place structures.
You position eight towers along the route, setting heights and orientations. The software automatically shows span lengths and ruling span.
Step 3: Define cables.
You select a twin ACSR conductor bundle from the library and assign it to the line. You add a steel earth wire at the tower peaks.
Step 4: Set load cases.
You enter the loading conditions required by your national code: everyday temperature, maximum operating temperature, high wind, ice with wind, and broken wire scenarios.
Step 5: Run calculations.
PLS-CADD calculates sag and tension for every span under every load case. It checks ground clearance, clearance to any obstacles you have defined, and phase-to-phase spacing.
Step 6: Export to PLS-TOWER.
For each tower, PLS-CADD sends the calculated conductor loads to PLS-TOWER. You check whether the tower members pass the structural analysis.
Step 7: Produce drawings.
PLS-CADD generates plan and profile sheets, stringing charts, and clearance reports ready for review.
This entire process stays within one integrated environment. Changes at any step propagate through the model.
What PLS-CADD Does Not Do
Understanding the boundaries helps set expectations.
PLS-CADD does not design towers or poles from scratch. It analyses structures you have defined or imported. If you need to create a new tower geometry, you do that in PLS-TOWER and then import it.
It does not perform detailed foundation design. It outputs foundation reactions, but you design the footings using geotechnical software or hand calculations.
It does not handle underground cables, substations, or protection systems. Its scope is the overhead line between terminal structures.
For software sales, licensing, and official support, Power Line Systems handles that directly. Northern Star Power Line Consultancy provides training and implementation consulting, not software sales.
How Engineers Typically Learn PLS-CADD
Most engineers start with the software manual and trial and error. This approach works eventually, but the learning curve is steep. PLS-CADD has accumulated features over three decades, and finding the efficient workflow for your specific application takes time.
Structured training shortens that process considerably. Interactive courses let you ask questions about your actual projects and learn the techniques that experienced users rely on daily.
Northern Star PLC has delivered PLS-CADD training worldwide since 2017. Courses cover everything from basic modelling through to advanced thermal uprating studies, and can be tailored to your organisation's codes and workflow requirements.
Ready to move beyond the manual?
View PLS-CADD course content and upcoming dates or explore bespoke implementation support for teams rolling out the software.
PLS-CADD Questions That Come Up in Practice
Can the PLS-CADD model both transmission and distribution lines?
Yes. The software handles voltage levels from low-voltage distribution through to EHV transmission. The workflow is identical; only the structure types, conductor sizes, and clearance requirements differ.
Does PLS-CADD work with survey data I already have?
PLS-CADD imports terrain data from LiDAR point clouds, photogrammetry, GPS surveys, and digitised maps. If your data is in a standard format, you can usually bring it straight into a project.
How do PLS-POLE and PLS-TOWER connect to PLS-CADD?
PLS-CADD sends calculated wire loads directly to the structural analysis modules. You can launch PLS-POLE or PLS-TOWER from within PLS-CADD, and results flow back into the line model without manual data transfer.
H3: Is PLS-CADD suitable for uprating existing overhead lines?
Absolutely. The software excels at uprating studies. You model the existing line, change the operating temperature or conductor, and immediately see which spans fail clearance checks at the new parameters.
H2: From Understanding the Model to Using It Well
PLS-CADD brings terrain, structures, cables, loads, and clearances into one connected model, so you can see how each design decision affects the line.
If you want to build practical skills with real Power Line workflows, explore Northern Star Power Line Consultancy's PLS-CADD training.
