How to Draw an Electrical Diagram for a Photovoltaic Installation and What Protections Should Be Included?

Photovoltaics Masters Institute

EasySolar electrical diagrams: How to Draw an Electrical Diagram for a Photovoltaic Installation and What Protections Should Be Included?

The easiest way to draw electrical diagrams for photovoltaic installations is by using the EasySolar app, where such diagrams, including all necessary components, can be automatically generated. A photovoltaic (PV) installation consists of several key components that must be correctly represented on the electrical diagram. Each of these components serves a specific function, and their proper placement and protection are crucial for the safety and efficiency of the system. In this article, we will discuss how to draw a PV installation diagram and the protections that should be included, along with the symbols used to represent them.

Key Elements of the Electrical Diagram for a Photovoltaic Installation

The PV installation diagram should include the following key components:

1. Photovoltaic Panels (PV modules)
-> Symbol: A rectangle or a set of rectangles representing PV panels.
-> Description: Indicate the number and power of the panels and their connection method (series, parallel, or a combination). PV panels generate direct current (DC).

2. Inverter
-> Symbol: A rectangle with an inverter label.
-> Description: The inverter converts direct current (DC) from the panels into alternating current (AC), which can be used in the home or fed back into the power grid.

3. Battery (if applicable)
–> Symbol: A rectangle with a battery symbol.
-> Description: In systems with energy storage, a battery is used to store electricity. Include the capacity and voltage of the batteries in the diagram.

4. Charge Controller (if applicable)
-> Symbol: A rectangle with a charge controller symbol.
-> Description: Used in off-grid and hybrid systems, it controls the charging process of the batteries, protecting them from overcharging.

5. Switches and Protections
-> Symbol: Switches (e.g., dashed lines) or fuses.
-> Description: Protective elements that safeguard the installation from overloading, short circuits, and surges.

6. AC and DC Distribution Boards
-> Symbol: Rectangles representing distribution boards.
-> Description: The DC distribution board includes protections on the DC side, while the AC distribution board handles protections on the AC side.

7. Energy Meter
-> Symbol: A rectangle with a meter symbol.
-> Description: The energy meter monitors the amount of energy produced by the system or fed into the grid.

8. Cable Connections
-> Symbol: Lines connecting the components.
-> Description: Connections between the components, where solid lines represent electrical cables.

9. Grounding (Earthing)
-> Symbol: A symbol for grounding (three decreasing horizontal lines).
-> Description: Indicates grounding points that protect the system from surges.

10. Power Grid (for on-grid systems)
->Symbol: A line with a grid label.
-> Description: Represents the connection to the electrical grid if the PV system is grid-tied (on-grid).

Protections in a Photovoltaic Installation

Protections are critical for safeguarding both the equipment and users. Depending on the type of system (on-grid, off-grid, hybrid), different protections are needed. Below are the most important protections.

Direct Current (DC) Protections

1. DC Circuit Breaker (DC Disconnector)
-> Symbol: An open, dashed square.
-> Description: Allows manual disconnection of the PV installation from the inverter for maintenance or in case of a fault.
->Location: Between the PV panels and the inverter.

2. DC Fuse
-> Symbol: A dashed line with a fuse symbol.
-> Description: Protects the DC circuit from overcurrent and short circuits.
-> Location: Between the PV panels and the inverter.

3. DC Surge Protection Device (SPD)
-> Symbol: A square with a lightning bolt.
-> Description: Protects the system from surges induced by lightning strikes.
-> Location: Between the PV panels and the inverter.

4. DC Overload Protection
-> Symbol: A dashed line with a circle.
-> Description: Protects against overloads in the DC circuit.

Alternating Current (AC) Protections

1. AC Circuit Breaker (AC Disconnector)
-> Symbol: Similar to the DC disconnector, but on the AC side.
-> Description: Allows manual disconnection of the inverter from the electrical grid.
-> Location: On the inverter’s output side, before connecting to the home or public grid.

2. AC Fuse
-> Symbol: AC fuse symbol, dashed line.
-> Description: Protects the AC circuit from overcurrent and short circuits.
-> Location: Between the inverter and the home distribution board.

3. AC Surge Protection Device (SPD)
-> Symbol: A square with a lightning bolt.
-> Description: Protects the system from surges on the AC side.
-> Location: On the AC side, between the inverter and the home distribution board.

5. Residual Current Device (RCD)
-> Symbol: A dashed line with the letter “R”.
-> Description: Protects against electric shock in the event of leakage currents.
-> Location: In the AC distribution board in home circuits.

Fire Protection Devices
-> Purpose: Protect the system from fire risk in case of equipment failure.
-> Location: Typically placed on both the DC and AC sides, depending on system design.

Protections for On-Grid Systems

1. Main Double-Pole Disconnect Switch
-> Purpose: Disconnects the PV system from the grid in case of failure.
-> Location: Between the inverter and the bidirectional energy meter.

2. Anti-Islanding Protection
-> Purpose: Prevents the inverter from generating power in case of a grid outage.
-> Location: Usually integrated into the inverter.

Protections for Off-Grid and Hybrid Systems

1. Battery Fuses
-> Purpose: Protects the batteries from overcurrent and short circuits.
-> Location: Between the batteries and the inverter or charge controller.

2. Charge Controller
-> Purpose: Protects the batteries from overcharging.
-> Location: Between the PV panels and the batteries.

Conclusion

The easiest way to create electrical diagrams for photovoltaic installations is by using the EasySolar app, which automatically generates diagrams that include all the necessary components and protections. When designing a photovoltaic installation diagram, it’s essential to include all the key components such as PV panels, inverter, distribution boards, meters, and protections that safeguard the system from various risks. EasySolar streamlines this process, ensuring that the diagrams are accurate, compliant with local standards, and save time by automating much of the design work.