Learn what overhead lines are, what they are for, and how to create them.
Do you want to define an electrical transport line to connect the substation of your project to the utility substation?
This article explains how you can create an overhead line (OHL) to connect your PV plant to the electricity grid and will highlight some helpful hints in doing so.
What are overhead lines?
An OHL is a user-defined path that will be added to the HV cabling layout. The OHL connects the plant substation, via a MV or HV cable, to the utility substation or other interconnection point. OHL can be configured by drawing a path in the KML file. Subsequently, pvDesign will place different towers and traces the HV cable as defined by the user.
Connecting the project’s substation to the utility’s substation
In the next example, by utilizing a customized overhead line, we can connect the substation (ST polygon) to the next connection point. In order to do so, we will need to create a path of at least two points with the first point at the substation polygon (ST).
OHL can be configured on the medium and high voltage levels. Depending on the interconnection facility used (Substation for HV or Switching and breaking station or MV), respectively a transmission or distribution line is configured. Both the distribution and transmission lines will be overhead, they will however follow different calculation models.
How to create custom overhead lines
There's two ways that you can create OHL or "Gen Tie". One would be to do it on google earth and upload the file to pvDesign. And the other would be to create it using the site creator inside the software.
After getting into the site creator interface (as per the article on how to create a site directly inside pvDesign), you will be able to select the "Path" box, and choose overhead line.
After defining your site's KML/KMZ file (as per the article on how to create a site), you can opt to customize your HV route following these steps:
1. Open the site's KML/KMZ file in Google Earth (desktop edition).
2. Inside the initial site folder, define the overhead line from the substation of your project (ST polygon) to the utility substation. To do so, you must use the path tool. The dedicated name for your path should be “OHL”
Right-click on the initial site folder and go to Add → Path
3. The final step is to save the whole folder (in other words the main folder) as a KML or a KMZ.
4. You can now upload the KML or KMZ file to pvDesign. Done!
There are some special cases and conditions needed to use this tool:
- The OHL should not intersect with itself
- An OHL route can only be used to connect the project substation's first point of the path inside the ST polygon to the utility substation (last point of the path).
- The placement of overhead power towers is not prevented by restricted areas (RA polygons)
- pvDesign will assess all the points defined in the path by the user, but might remove or add points if necessary to define the position of each tower.
- It may happen that your overhead line is not feasible due to the incoherence between the capacity, voltage, and/or line length. If this happens, you will receive a warning in the platform.
If this happens, a warning will be displayed on the platform and if you generate a design with this warning, the OHLs documentation will not be generated.
To solve this problem try to change the high voltage (if you are using aSubstation) or the medium voltage (if you are using a Switching and breaking station) at the grid point tab to obtain the overhead line's results.
For any other questions or more information regarding this topic, you can contact us at: email@example.com