Three line diagram vs one line diagram

What is a three line electrical diagram? What does it differ from one line diagram?

I started for a volunteering for a foundation who installs solar systems.

During the installation, we were looking at one line diagrams and they told that we will need three line diagrams for the permit process. What's the difference?


The one line diagram (also called single line diagram or drawing) is the electrical system drawing that shows the main items within the solar system and how they are interconnecting eachother without giving any details.

On a one line diagram (regardless of the system's properties, such as AC, DC, 3 three phase etc.) the connections are represented as lines.

On a three line diagram, however, you can see the positive, negative, ground cables of a DC system, and L1, L2, (L3 on three phase) Neutral and Ground cables on an AC system. Each positive and negative line is represented as a single line.

The connection from a PV module to an inverter is represented with only one line on a single line drawing, whereas the same connection is represented as three lines (positive, negative, ground) on a three line drawing.

For your convenience, CivicSolar could provide the one line or three line diagrams of the solar PV system you are working on. We may also provide you some samples if you are going to use it for your education. Just contact us via email or telephone.