Hi to everyone, 

What can cause to burnt this panels up to this level. Of course not mine but pasted from Facebook group. 

There could be various reasons for the failure and damage in your picture but the most common hazard on solar arrays is ARC FLASH. 

The types of Arc Flash that can be generated within the solar industry are another major risk. With arcs capable of reaching more than 3000 degrees Celsius in temperature, these arcs not only cause fires but can also melt materials such as glass and metals including copper and aluminium. This can subsequently ignite any combustible materials and items in the surrounding area. In the solar industry, it is not only the direct risks of arc flash that must be considered but also the many possible indirect risks, too.

Improper crimping of MC4 connectors, loose connection in combiners, damaged solar cables ,damaged solar panels(micro cracks) can all lead to arc flash. Great care need to be taken when installing solar panels as dc is not as forgiving as ac curcuits.