Hi dilmarfjunior
Thanks for your interest in Lumion.
The problem is a known issue with some Dell Precision Tower 5810, and the lack of a suitable power supply to support the high performance GTX 1080 Ti card you have in the PC. Usually we find that there may be a low 400W supply, or a supply that does not provide adequate continuous supply to the 12 volt bridge.
When Lumion starts rendering it makes use of all the performance of the graphics card, and if the power supply is inadequate, then that can cause the PC to restart.
Just to verify with you that it is the PC is restarting, and not Lumion is crashing to the desktop?
I don't know what your upgrade options are in terms of power supplies, but you'd need to ask Dell if they can replace it with an 80+ Gold- or Titanium-rated power supply with a Wattage greater than 700W, and guarantee that it will work with your GTX 1080 Ti graphics card. There's more information about power supplies versus high-end graphics cards like the GTX 1080 in this Knowledge Base article:
Which power supply do you need?There is a possible solution.
The process involves limiting the power to the graphics card. It means that the graphics card is running slower, so renders will take longer than on a system where the power supply and graphics cards are working correctly

. So it's not a fix, but a workaround to get the hardware working together that no longer causes PC systems to restart.
Here are the steps:
1. Download and install 'MSI Afterburner via the 'Downloads' tab on this page:
https://www.msi.com/page/afterburner2. Start 'MSI Afterburner' and click on the 'Settings' button:
3. Tick these boxes in the 'Settings' menu if they're not already ticked and click 'OK':
4) It will ask you if you want to restart the PC. Click 'OK' to go ahead.
5. After restarting the PC, 'MSI Afterburner' should now be running in the task tray.
Click on this icon to open the 'MSI Afterburner' window again:
6. Try to set the 'Power limit to 50% and click on the tick button to accept the changes (Let me know if this slider isn't available for you):
7. Save all files in all open apps to prevent data loss if the PC still restarts when rendering images with 'Hyperlight' in Lumion.
8. Start Lumion, and load one of the demo scenes.
9. Simply add one of the new 'Styles' to a Photo or Clip and then render a 'Print' or 'Poster' resolution image to check if the PC restarts.

If that works at 50% then, you can test higher 'Power limit' values to find the "sweet spot". Try 60%, 70%, 80% and 90% for example.
Let us know if it works or not.
Thanks in advance.
The only remaining alternative is to ask Dell if there is a way to replace the power supply with a more powerful 80+ gold- or titanium-rated power supply, and of course, ask them to guarantee that doing so will work with your GTX graphics card.