Btw I noticed that the cast every 10 minutes will also interrupt any media that might be playing. So now i created a scriptfile that I run instead of the single CATT command. The script will check if anything is playing on the Google Hub. So in the automation I now call /config/cast.sh which contains:
if ! catt -d "Living Room display" status | grep 'PLAYING' ; then
catt -d "Living Room display" cast_site http://192.168.178.87:8123/lovelace-test/0
fi
Note: I put the cast.sh file in the config folder so that it will remain there after a complete reboot.