Voting one per day

Nope. It is per post per day then it is possible. It is not possible sitewide.

I have voting per post. So how can I do this?

I found this hook:
wp_postratings_cookie_expiration
but will it work when I have IP checking too?

Sorry I didn’t miss the IP in your question, it will work for cookie only. IP can only be rated once.

Thanks for help.