No it doesn't use your SP it uses your VP (Voting Power). You can check on steemd under your user name to see what it is. I think it replenishes roughly every 24hrs and is a percentage (0-100). Every time you vote or post it goes down.
As for self upvoting I commented on this too in my last post here:
https://steemit.com/steemit/@thecryptofiend/the-whale-issue-and-how-they-are-the-new-nobility
The TLDR of it is that I think there should be a cap of value on self-voting payments e.g. $1. This would help reduce the impact of whales and big SP holders self-voting themselves right to the top. For minnows it doesn't really matter because the impact is tiny.
great thanks for the information.
It does seem a bit strange, its like a punishment for spending time on the site.
it does prevent spamming i suppose but there is a time delay for that..
Thanks for the link too I will check out your point of view too.
Just about whales, they obviously have more weight with their vote for other people so I don't see why it should be capped for themselves. If they can make other people posts visible they should be able to do it for themselves? I think this is in the interest of steem and how are continuing to incentivise holding steempower