Fixed-tilt cabling

To start working on cabling, you should have the following established and defined:

• Frames with stringing & electrical devices placed;

• Trench lines were drawn throughout the PV area.

Trench lines

Start by opening the Cabling section of the Electrical Design menu and click on Select PV areas - select the PV area boundary line and press Space or Enter on the keyboard. Example below:

You may then draw the trench lines using basic AutoCAD polylines. It is crucial for the trench lines to either touch or overlap each other - this will allow PVcase to operate optimally.

Once all trench lines are created, you may then return to the Cabling section in the Electrical design menu and click on Select trench lines. Select the newly-drawn trench polylines and press Space or Enter on the keyboard. Example below:

Note: if the trench lines were modified or new trench lines were drawn do not forget to reselect them in order to implement the changes.

There are some more features when it comes to trench lines:

• Clear - lets you deselect all the trench lines

• Clear specific - lets you deselect specific trench lines

• Indicate -  highlights all currently selected trench lines

Before starting the cabling, choose the Cable stickiness to the trench line. If you choose the option the Shortest path, the cabling algorithm is programmed to find the shortest cable route possible. But sometimes the result does not meet the expectations. In that case, you can toggle the cabling algorithm to follow the trench more strictly by choosing Stick. This should help keep the cable route within the defined trench lines.

Cabling

Now you can choose the Cabling type from the drop-down menu:

• AC cabling

• DC cabling

• HV cabling

  

  In the case a system with Central inverters is used, instead of AC and DC cabling, there will be the options to do DC Main cabling (from combiner box to inverter) and DC string cables (from strings to combiners).

Let us start with DC cabling. After choosing the cabling type, you need to choose Cabling generation type. For that, you have 2 options:

• Auto - all cables for strings and devices will be generated automatically according to the selected trenches.

• Semi-auto - mode allows the selection of individual strings or devices as well as to specify in more detail the route of the cable. That ultimately forces the software to design the cabling according to the trench lines that are being selected and not the software estimating which ones to use from a handful of selected trench lines.

We will use Auto generation. The next step would be to specify the details of cable management. In order to do that, go to Cable separation:

After enabling the checkbox in the pop-up window, you can set the Number of cables per layer, the Distance from the trench sides to the cables, and lastly Cable center separation Vertical and Horizontal.

Under voltage drop you can:

• choose between IEC and NEC standards
• set a minimum CSA, we will not go below your choice
• set the nominal AC voltage of your inverters (AC V)
• select the material (aluminum or copper)
• set the voltage drop you want to reach
• set the nominal voltage (Vmpp) and current (Impp) of your modules

Once all parameters are adjusted to your needs, click on Generate DC cabling. You will then be prompted to select the transformer - having done so, press Space or Enter on the keyboard. Example below:

As you can see in the image above, the DC cabling was generated for all the strings and devices for this transformer. Each cable run is drawn as its own, thin blue polyline, which will be accounted for in the Bill of Materials.

The same process is applicable to AC cabling. From the drop-down menu choose AC cabling, leave the generation type as Auto, cables stickiness value to the Stick setting, and lastly click on Generate AC cabling. You will be prompted to select the transformer - having done so, press Space or Enter on the keyboard. The cabling for AC will be purple. Example below:

PVcase also has the option to create HV cabling runs from inverters & transformers to grid-connected sub-stations. Per European standards, these systems are referred to as High Voltage. To do so, one should create a new, additional block much in the same way as it was done for the transformer. You may draw a rectangle, then type BLOCK to open the Block definition menu, where you may select the rectangle & give the new block a name. One should make sure that there are trench lines between the substation and transformer stations. Example below:

To start, you need to choose HV cabling from the drop-down menu. Next, you need to select what kind of HV run you would want to implement:

• Regular - connects Transformer Stations in the order that you would like them to be connected.

• Ring - it will behave the same as the regular HV cabling option the only difference is that the final Transformer Station will loop back to the Grid Connection to complete the ring.

In this case, choose the standard option - Regular. Finally, before generating the HV cabling you need to define Cable stickiness to trench - in our case let's leave it at the Stick setting. To generate the cables click on Generate HV cabling. You will be prompted to select the substation block and press Space or Enter to continue. Then you should select the transformers you want to connect to the substation. To finalize the process, press Space or Enter on the keyboard, and now you should have HV cable runs on your drawing. Example below:

You can also convert the cables from 2D representations into more realistic 3D segments. For that, you need to define your Cable placement in relation to the ground. It can either be

Below or Above the ground;

In this case, we will set it to the Below setting. The next step would be to define the Minimum cable depth. Then click Convert to 3D, which will prompt you to select transformer and press Space or Enter on the keyboard. You are then prompted to select if you want to perform this for the DC, AC, HV, or ALL types of cables. In this case, choose to do it for ALL cables. Example below:

After the cabling has been generated and converted to 3D, you may perform a cable cross-section. In order to perform this action, click on the Export cross-section button, then you are prompted to select the trench line, and to finalize, click to place the cross-section at your desired location. If you were to zoom in, you would be able to see the arrangement of our cables below the ground. Example below:

To observe this change, you may switch to SW Isometric in AutoCAD and zoom in. Should you prefer to do it manually, you may rotate the screen free-hand by holding the left shift and pressing on the mouse scroll wheel. The cables should now be visually moving from the frames, down into the terrain, and following the trench lines. Example below:

Troubleshooting tips

Cabling for some devices is not possible. Please check if the intersection with trench lines is possible for all devices.

This error means that devices could not be connected with cable polylines because the trench line is either too far away or cannot be located from the device location when it's checking the left or right of itself for a trench line. The solution is to check whether all trench polylines reach all electrical devices and if not extend.

Trench polylines are not intersecting with each other

Formulas used for voltage drop calculation