Help adding seconds to a formula

Hello! I need some help adding seconds into a calculated column

This is the formula I got now:

=IF(INT(Minuter/60)<10;"0"&INT(Minuter/60);INT(Minuter/60))&":"&IF(ROUND((((Minuter/60)-INT(Minuter/60))*60);0)<10;"0"&ROUND((((Minuter/60)-INT(Minuter/60))*60);0);ROUND((((Minuter/60)-INT(Minuter/60))*60);0)))

Why I use this code is because I want it to exceed 24 hours, which it does in "hh:mm" and it works just fine. Now I would like to add seconds so it shows "hh:mm:ss". Anyone got any ideés how? 

It looks like this atm:

Thanks!