From Plot Polygon to Short-Circuit Currents: How I Built a Substation Generator

Designing an electrical substation from scratch is a complex engineering challenge. It involves site selection, electrical calculations, equipment sizing, and compliance with numerous standards. For many years, this process was manual, time-consuming, and error-prone. But recent developments in automation are changing the game. A new project, detailed by a team of engineers on Habr, demonstrates how a custom generator can transform a simple plot polygon into a full-fledged substation model, complete with short-circuit current calculations. This article explores their approach, the tools they used, and the practical implications for electrical engineers.

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The Problem: Manual Substation Design

Traditionally, designing a substation begins with a plot of land. An engineer takes the polygon coordinates, manually determines the optimal arrangement of transformers, switchgear, and busbars, and then performs electrical calculations. This process is not only labor-intensive but also highly repetitive. Each new project requires starting from scratch, with little reuse of previous work. The team behind this project encountered these exact frustrations: “We were spending weeks on calculations that could be automated, and errors were common due to manual data entry.”

The Solution: An Automated Generator

The developers decided to create a software tool that automates the entire pipeline. Their generator takes a plot polygon (defined by geographic coordinates or a CAD file) as input and outputs a complete substation design, including:

• Equipment layout: Optimal placement of transformers, circuit breakers, disconnectors, and busbars based on the site’s shape and size.
• Electrical parameters: Calculation of rated currents, short-circuit currents (both symmetrical and asymmetrical), and thermal withstand capabilities.
• Compliance checks: Verification against IEC and IEEE standards, such as IEC 60909 for short-circuit currents.

The generator is built using a combination of open-source libraries and custom algorithms. For example, the developers used Shapely for polygon geometry processing and Pyomo for optimization of layout. The electrical calculations are based on standard formulas from IEC 60909, which are implemented in a dedicated module.

How It Works: From Polygon to Currents

Let’s break down the workflow step by step:

1. Input: The user provides a plot polygon in GeoJSON or DXF format. The generator also requires parameters like voltage level, transformer power rating, and system impedance.
2. Polygon Processing: The tool analyzes the polygon to determine usable area, considering setbacks and safety clearances. It then generates a candidate layout using a grid-based optimization algorithm.
3. Equipment Placement: Based on the layout, the generator assigns positions for each piece of equipment. For instance, transformers are placed near the center of gravity of the load, while switchgear is positioned for easy access.
4. Electrical Calculations: Using the assigned equipment and system parameters, the tool computes:
5. Rated currents: Based on transformer power and voltage.
6. Short-circuit currents: Both three-phase and line-to-ground faults, using the IEC 60909 method.
7. Thermal and dynamic stresses: Ensuring that equipment can withstand fault conditions.
8. Output: The generator produces a report that includes a CAD drawing (in DXF format) and a table of electrical parameters.

The developers note that the short-circuit current calculation was particularly challenging. They had to account for multiple sources (utility grid, local generators, motors) and the impedance of each element. The final algorithm was validated against manual calculations from an existing substation design, achieving an accuracy within 2%.

Practical Applications and Case Study

The generator has already been tested on a real-world project: a 110/10 kV substation for a renewable energy park. The plot polygon was irregular, with a narrow corridor for cable routing. The generator produced a layout that minimized cable length and reduced losses by 8% compared to the manual design. The short-circuit currents were calculated at 12.5 kA for a three-phase fault, which matched the manual calculation to within 0.3 kA.

This case study demonstrates the potential of automation in substation design. According to the developers, the tool reduced design time from three weeks to three days — a 86% improvement. Errors were also reduced, as the automated calculations eliminated manual transcription mistakes.

Technical Details and Challenges

The developers faced several technical hurdles:

• Geometry to topology: Converting a polygon into a functional layout requires algorithms that consider both space constraints and electrical connectivity. The team used a Voronoi diagram approach to cluster equipment logically.
• Impedance modeling: The short-circuit calculation requires accurate impedance values for transformers, cables, and busbars. The generator includes a database of standard equipment parameters, but users can also input custom values.
• Standards compliance: Ensuring the design meets IEC 60909 and local grid codes was non-trivial. The team implemented rule checks that flag violations, such as insufficient clearance between live parts.

The tool is written in Python, with a web-based frontend for user input and visualization. The developers plan to release it as an open-source project, which could benefit the broader engineering community.

Comparison with Traditional Tools

To understand the value of this generator, it’s useful to compare it with existing solutions:

As the table shows, the generator offers significant advantages in speed, accuracy, and cost. However, it requires initial setup and customization for each project, which may be a barrier for small firms.

What This Means for Electrical Engineers

This project is part of a broader trend toward automation in power engineering. Tools like this can free engineers from repetitive calculations, allowing them to focus on creative aspects like system optimization and innovation. For example, the generator can quickly test multiple layout configurations, helping engineers find the most cost-effective solution.

That said, the developers caution that their tool is not a replacement for human expertise. “Automation handles the routine, but engineers must still validate the output and apply judgment for non-standard situations,” they write. This is especially true for complex substations with unusual topologies or high fault currents.

Future Directions

The team is already working on enhancements. They plan to add:
- Dynamic simulation: Modeling transient stability during faults.
- BIM integration: Exporting designs to Building Information Modeling (BIM) software for construction planning.
- Machine learning: Using AI to optimize layout based on historical project data.

These features could further reduce design time and improve quality, making substation design accessible to a wider range of professionals.

Conclusion

The substation generator project shows that automation is not just for IT — it’s transforming traditional engineering disciplines. By taking a plot polygon and producing a complete design with short-circuit currents, the tool demonstrates how open-source algorithms can solve real-world problems. For engineers, it means faster projects, fewer errors, and more time for innovation. As the developers plan to release the code publicly, the electrical engineering community may soon have a powerful new resource at its fingertips.

Whether you’re a seasoned power engineer or a student learning the trade, this project offers a glimpse into the future of substation design. The next time you look at a plot of land, remember: with the right algorithms, it could become a fully analyzed, code-compliant substation in just a few days.