UPS compatible with seasonic S12-II bronze 520w PSU

the problem might be with the non sine-wave output of your ups.
some seasonic psu and many others which have got an active pfc circiut inside the psu are incompatible with non sine wave outputs from these cheap backups,
if u want to solve this problem try a ups which has a sine wave output.
try www.apc.com and search for a ups which has got a pure sine wave output (not a simulated sine wave)

also the reason that some other power supplies work with this ups is that those psu's
may be a non active pfc power supply which are very cheap and does not care about
the wave form of the backup current. this type of psu's are not good for your computer, but your seasonic psu is with active pfc and that's why it turns off when seeing a bad waveform output from your ups's battery backup,also this does not depend upon where you live this is because of a bad ups.

ups in india is like a neccesity i lived there for 2 years country side up north (punjab)

the power outage there is ridiculous it was like every 3 hours power was gone for like an hour

anyway im also buying a seasonic m12ii bronze 520w

do we really need a pure sine wave? cause those are a bit expensive
here is an thread discussing about pure sine wave ups
http://www.tomshardware.com/forum/252532-28-purest-sine...

I have done lots of reading on the internet. I know that pure sine wave ups will work but that is simply out of my budget. seasonic also says that psu will work with all standby (which are cheapest) and online ups. But there is no guarantee with line interactive ups which are most commonly available in market. seasonic says chances are 70-80 % for it to work.

Till now I have read that luminous 600VA works, APC Backup series and APC Backup ES series works.

if an active pfc pwer supply is working fine on the standby ups without any issues then you are good to go, in your case if the apc backup series will work then go for it,but confirm it first,
or it will be a waste of money..

let me know how it turns out im also planning to buy the same psu and pair it with a ups

Brought home APC BackUP RS Series 600VA/360V ( BR600CI-IN ) on a leap of faith and its working fine.
I haven't done any extensive tests but I was playing a not-so intensive game NFS-MW(2005) when power failed.
I successfully exited the game and shut down my PC. Another time I was doing some simple tasks and lost power.
I waited 2-3 minutes and power came back. So, I guess it'll work.

This model has a way to program AVR to work with less, medium and high sensitive equipments. Just check the manual, if you buy it.

it will work for you from now on since you had no problem for 2-3 minutes earlier you said that it didnt even work for 5 seconds dont worry!!