In the engineering and construction of a solar project, technical drawings are the “language” used to communicate the design. While they might look similar to the untrained eye, SLD, Layout, and GA Drawings each focus on a different layer of the project: the electrical logic, the spatial positioning, and the physical assembly.
1. Single Line Diagram (SLD)
The SLD is the electrical blueprint of the system. It uses a single line to represent all the phases of a multi-wire circuit (e.g., a three-phase system) to keep the diagram readable.
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Focus: Electrical connectivity and logic.
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Key Components: * DC Side: Solar strings, DC fuses, and surge protection.
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Conversion: Inverters and their specific ratings (kW).
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AC Side: Circuit breakers, transformers, and the “Point of Interconnection” (POI) to the grid.
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Safety: Grounding/earthing connections and protection relays.
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Primary Use: Used by electrical engineers for load flow analysis and by technicians for wiring and troubleshooting.
2. Layout Drawing
The Layout Drawing (often called a Site Plan) is a birds-eye view of the entire project. It focuses on how the components fit within the physical boundaries of the site.
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Focus: Spatial organization and site utilization.
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Key Components: * Array Placement: Exactly where the solar rows are located.
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Clearances: Setbacks from property lines, trees, or roof edges.
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Equipment Pad: The physical location of the inverters and transformers.
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Cable Routing: The “trenches” or conduits where wires travel from the panels to the inverter.
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Primary Use: Used by site managers to coordinate heavy machinery and by installers to mark out where structures will be bolted down.
3. General Arrangement (GA) Drawing
While the Layout shows where things go, the GA Drawing shows how they are built and fit together. It provides specific dimensions and structural details.
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Focus: Detailed assembly and structural dimensions.
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Key Components: * Structure Views: Front, side, and top views of the Module Mounting Structure (MMS).
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Tilt & Orientation: The specific angle (e.g., 25°) and azimuth (e.g., 180° South) of the panels.
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Foundation Details: Cross-sections showing how deep a pile is driven or the size of a concrete ballast block.
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Mechanical Clearances: Minimum distance from the bottom of the panel to the ground (ground clearance).
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Primary Use: Used by civil and structural teams for the physical installation of the racking and panels.
Comparison Summary
| Drawing Type | Question it Answers | Typical Scale | Primary User |
| SLD | How is it wired? | Not to scale | Electrician / Engineer |
| Layout | Where does it go? | 1:500 or 1:1000 | Site Manager |
| GA Drawing | How is it built? | 1:20 or 1:50 | Structural Installer |
Would you like me to provide a specific list of the symbols used in an SLD, or perhaps a checklist of what to look for when reviewing a Layout drawing?
How to Read Electrical Single Line Diagrams (SLD)
This video provides a practical, step-by-step guide on how to interpret the symbols and logic used in electrical single line diagrams, which is essential for understanding the electrical design of a solar system.