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What is a Single Line Diagram (SLD)?

Single line diagrams (SLDs) are simplified graphical representations of electrical systems, showing components, connections, and power flow.

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    Single-Line Diagram (SLD)

    Solar plan sets are integral for any PV (Photovoltaic) installer, EPC, or construction company looking to streamline their solar panel installation process. An integral part of these sets is the single-line diagram. But what is a single-line diagram?

    What is a Single Line Diagram?

    A single-line diagram, or SLD, is a simplified notation for representing a three-phase power system. Instead of illustrating all three phases, the SLD represents the entire power system via a single line, focusing on the main components such as the power source, power distribution pathways, electrical equipment, and protection devices.

    In the context of solar plan sets, an SLD provides an overview of how all the critical components of a solar system are connected. It includes the layout and design of the PV array, the circuit conductors, the rating and size of the circuit breakers, and the incoming power from the grid.

    Single-Line vs Schematic Diagrams: Key Differences

    While both single-line and schematic diagrams play essential roles in system design, understanding their distinctions is crucial.

    A single-line diagram (SLD) is a condensed method for representing a three-phase power system. The SLD simplifies the power system by illustrating it with single lines and symbols. It focuses mainly on the power flow and primary components such as power sources, power distribution pathways, and crucial electrical equipment.

    On the other hand, a schematic diagram goes into greater depth. It illustrates detailed wiring and connections between all components, providing a comprehensive view of the entire system.

    To put it in simple terms:

    • Single-Line Diagrams:
      • Provides a simplified view of the system.
      • Emphasizes on power flow and primary components.
      • Useful for understanding the general working of the system.
    • Schematic Diagrams:
      • Offers a detailed representation of connections.
      • Shows the exact wiring and interconnections between all components.
      • Ideal for technical purposes such as installation, troubleshooting, and maintenance.

    Understanding the differences between these two types of diagrams can help professionals choose the appropriate one based on their specific needs and the level of detail required.

    Importance of Single-Line Diagrams

    Having a professionally drafted SLD offers multiple benefits:

    • Simplifies Complexity: The single-line diagram simplifies the complexity of the electrical system, making it easier to understand.
    • Facilitates Planning: The SLD provides an overall view of the power system, facilitating planning and decision-making processes.
    • Enhances Safety: By clearly marking protection devices, the SLD enhances safety by helping to prevent short circuits and electrical overloads.
    • Aids Troubleshooting: If issues arise, the SLD can serve as a guide for troubleshooting and maintenance.

    Decoding the Single Line Diagram

    Let’s imagine a scenario where a commercial building has decided to install a 100 kW solar PV system along with a battery backup. Here’s how each component is represented and calculated in the single-line diagram:

    1. PV Array: The diagram displays the PV array as a single line or symbol. For our example, the size and rating of the PV array is determined to be 100 kW. This rating plays a crucial role in determining the size and ratings of the circuit conductors, circuit breakers, and any other related equipment.
    2. Inverter: The diagram further depicts how power flows from the PV array to an inverter where DC power is converted to AC power. The inverter’s rating is typically the same as the PV array’s capacity, so in this instance, the inverter rating would also be 100 kW.
    3. Battery Storage System: The single-line diagram also portrays the battery storage system, its connection to the inverter, and its disconnection means. The size of the battery storage system is set based on the client’s backup power requirements.
    4. Grid Connection: Finally, the diagram represents the connection to the grid. This includes the main service panel that houses the circuit breakers designed to safeguard the system against short circuits.

    By comprehending these calculations and their respective representations in the single-line diagram, stakeholders can easily interpret the layout of the solar PV system, along with its interconnections.

    Read More: Solar + Battery Plan Sets Starting at $299

    Why Outsource Your Solar Drafting Services?

    Outsourcing your solar drafting services to a specialist like SolarPlanSets offers numerous benefits:

    • Expertise: SolarPlanSets has extensive experience in drafting solar plan sets, solar + battery backup designs, and standby generator plan sets.
    • Cost-Efficiency: Outsourcing reduces costs, as you only pay for the services when needed. This saves on hiring and laying off personnel depending on project availability.
    • Scalability: Whether you’re installing a small residential PV system or a large commercial system, SolarPlanSets can scale its services to match your needs.

    Single Line Diagram FAQs

    Here are the top 10 questions about single-line diagrams (SLD) we are asked most often by our readers and customers. If you don’t see your question answered, feel free to reach out to our support team for help.

    1. What is a single-line diagram?

    A single-line diagram (SLD) is a simplified graphical representation of an electrical system, showing the main components, connections, and power flow using symbols and lines. It’s a useful tool for understanding and designing electrical systems.

    1. Why are single-line diagrams important?

    SLDs are important because they provide a clear and concise overview of an electrical system’s layout, components, and connections, making it easier to understand, design, troubleshoot, and maintain the system.

    1. What are the main components of a single-line diagram?

    The main components of an SLD include generators, transformers, circuit breakers, switches, busbars, loads, and protective devices like relays and fuses. These components are represented by standardized symbols.

    1. How do I read a single-line diagram?

    To read an SLD, start by identifying the symbols representing the main components and their connections. Follow the lines to understand the power flow direction and relationships between components. Look for labels and annotations that provide additional information.

    1. What is the difference between a single-line diagram and a schematic diagram?

    A single-line diagram represents an electrical system using single lines and symbols, focusing on the power flow and main components. In contrast, a schematic diagram shows the detailed wiring and connections between all components, providing more in-depth information.

    1. How are single-line diagrams used in power system analysis?

    SLDs are used in power system analysis to study the system’s performance, stability, and reliability. They help in identifying potential issues, planning system expansions, and evaluating the impact of changes in the system.

    1. What software can I use to create single-line diagrams?

    There are various software tools available for creating SLDs, such as AutoCAD, SmartDraw, and ETAP. These tools offer libraries of symbols, templates, and features that make it easy to design and customize SLDs.

    1. What information should I include in a single-line diagram?

    An SLD should include information about the main components, their connections, power flow direction, voltage levels, and any protective devices. It may also include annotations, labels, and legends to provide additional details and context.

    1. What are the common symbols used in single-line diagrams?

    Common symbols in SLDs include circles for generators, squares for transformers, lines for busbars, and various shapes for switches, circuit breakers, and protective devices. Each symbol represents a specific component or function in the electrical system.

    1. How can I ensure the accuracy and completeness of my single-line diagram?

    To ensure the accuracy and completeness of your SLD, start by gathering all relevant information about the electrical system, including component specifications, connections, and voltage levels. Double-check your work, use standardized symbols, and consider having a colleague or expert review the diagram for accuracy and clarity.


    Understanding single-line diagrams and their role in solar plan sets can enhance your solar installation process. If you’re looking for expert assistance in drafting solar plan sets, SolarPlanSets is your go-to provider. Our expertise and dedication to quality ensure you receive a comprehensive, easy-to-understand plan set to streamline your solar installations.

    Reach out to us to learn more about our services or to order your solar plan sets. Harness the power of the sun efficiently with SolarPlanSets.

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