When it comes to transmission line engineering, Plan and Profile Drawings (P&P Drawings) form the backbone of any reliable design package. These drawings are the bridge between the conceptual survey data and the physical construction of transmission lines on site.
For engineers, contractors, and design reviewers, understanding how these drawings are prepared, what information they contain, and why precision matters is essential. According to TES-P-122.07 REV.02 (SEC Standard), the Plan & Profile Drawing serves as the master layout representing the complete geometry, topography, and alignment of a transmission line route.
1. General Overview
The Plan & Profile Drawing provides a comprehensive graphical representation of the transmission line route in both horizontal and vertical planes.
- Plan View: Shows the route alignment, tower locations, right-of-way (ROW) limits, crossing details, access roads, and important ground features such as rivers, highways, railways, and habitations.
- Profile View: Represents the elevation of the terrain along the line route, tower spotting levels, and conductor clearance envelopes.
Together, these two views ensure that design, construction, and maintenance teams have a clear understanding of how the line interacts with the terrain and existing infrastructure.
In essence, Plan & Profile drawings are the blueprint of the route—providing every detail necessary to translate design intent into a safe, compliant, and constructible transmission system.
2. Importance in Transmission Line Design
The Plan & Profile Drawing is not just a drawing—it is an engineering document that dictates critical design parameters such as:
- Tower type and location
- Conductor sag and clearance
- Ground profile and obstacle management
- Line deviation angles and tension sectioning
- Crossing and safety clearances
Accurate P&P drawings prevent costly field modifications and ensure that the line adheres to utility standards like the SEC (Saudi Electricity Company) and international norms such as IEC and IEEE.
3. Drawing Preparation
Preparing a Plan & Profile Drawing is a multi-step process requiring both field and office work. As per SEC’s TES-P-122.07 standard, the workflow generally includes:
a) Survey Data Collection
- Detailed topographical survey of the proposed route using total stations, GPS, or LiDAR.
- Collection of terrain elevations, ground features, and existing utilities within the corridor.
- Route coordinates must be established in a defined coordinate system (usually WGS-84 / UTM projection).
b) Alignment Finalization
- Selection of the optimized centerline route based on survey data and preliminary design.
- Defining deviation points, turning angles, and tangent sections.
- Incorporating ROW constraints, land use, and accessibility.
c) Data Processing & Drafting
Once field data is validated, drafting begins using CAD software—typically AutoCAD, MicroStation, or specialized line design tools like PLS-CADD.
Each drawing sheet is prepared at an appropriate scale, usually 1:2000 horizontal and 1:200 vertical, depending on the length and complexity of the section.
d) Drawing Sheet Layout
- Each drawing sheet includes a Title Block, Revision Table, and Legend of Symbols.
- Plan and Profile are aligned vertically—plan on top, profile at bottom—for easy interpretation.
- The chainage (distance along line) is common for both plan and profile views.
e) Information to be Shown in Plan View
- Transmission line alignment and tower numbering.
- Property boundaries, existing utilities, roads, rivers, and crossing features.
- ROW width (typically 30 m or as per voltage level).
- Geographic coordinates and north arrow.
- Substation connection points and reference benchmarks.
f) Information to be Shown in Profile View
- Natural ground profile along the centerline.
- Tower base levels, tower spotting, and span lengths.
- Conductor and ground wire clearance envelopes (sag curves).
- Crossings with roads, pipelines, or communication lines showing required clearance.
- Sectional views for special features such as valleys or rivers.
g) Review & Approval
After preparation, each drawing is reviewed internally for accuracy, scale, and compliance with SEC standards. Revisions are documented in the revision block before final approval and issue for construction (IFC).
4. Features of a Standard Plan & Profile Drawing
The SEC standard defines a set of mandatory features and formatting guidelines to ensure uniformity and clarity across all projects.
a) Title Block
Located at the bottom-right corner, the title block contains:
- Project name and location
- Transmission line voltage (e.g., 132 kV, 230 kV, 380 kV)
- Drawing title and sheet number
- Drawing number referencing TES-P-122.07
- Date, revision, and responsible design engineer signatures
b) Grid System
Each drawing uses a chainage grid to correlate plan and profile coordinates. Chainage intervals are generally marked every 50 m or 100 m, depending on terrain variation.
c) Tower Spotting Table
A separate table lists:
- Tower number
- Type (suspension, tension, dead-end)
- Span length
- Tower base elevation
- Conductor and earth-wire attachment heights
This helps site engineers easily match field-installed towers with their corresponding design data.
d) Crossing Details
Crossings are one of the most critical parts of a plan & profile drawing. For each crossing, the drawing must show:
- Type of crossing (road, pipeline, power line, etc.)
- Clearance at maximum sag
- Coordinates and reference chainage
- Applicable safety codes (SEC, NESC, IEC)
e) Reference Data
Benchmarks, survey control points, and coordinates must be clearly labeled to assist construction teams during staking and verification.
f) Legends & Symbols
Every drawing must contain a standard legend defining line types, hatching, and color codes used for:
- ROW boundaries
- Roads and rivers
- Existing utilities
- Tower types
- Special notes (e.g., proposed vs. existing lines)
5. Typical Workflow Integration
The Plan & Profile Drawing is not a standalone output—it integrates with other design deliverables like:
- Transmission Line Route Survey Report
- Tower Schedule and Spotting Data
- Sag-Tension Calculations
- Foundation and Structural Drawings
Once all these components are finalized, the P&P Drawing becomes the master reference document for the construction and quality assurance phases.
6. Key Benefits of a Well-Prepared P&P Drawing
- Ensures engineering accuracy and eliminates ambiguity.
- Reduces construction rework and delays.
- Provides legal clarity for ROW acquisition.
- Improves safety compliance with clearance regulations.
- Enables future maintenance and line uprating studies.
A properly prepared Plan & Profile Drawing essentially represents the DNA of a transmission line—everything else in the project builds upon it.
Conclusion
In the realm of overhead transmission line design, Plan & Profile Drawings are indispensable. They combine survey accuracy, engineering judgment, and construction foresight into one unified representation of the route. When prepared as per TES-P-122.07 REV.02 (SEC Standard), these drawings not only satisfy regulatory requirements but also ensure smooth project execution from concept to commissioning.
For design engineers, mastering this drawing preparation process is not just about drafting—it’s about ensuring the integrity, safety, and longevity of the entire transmission network.
